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• Add controls dynamically on button click in asp.net mvc

  - by Ashwani K

  Hello All: I am creating an asp.net MVC application in which I want to provide a functionality to add a controls dynamically. I have a form in which there are 2 text boxes for First Name and Last name which serve as a single control. Now an user can add any number of this group of controls. I am able to add these controls on the page using java script. But I do not know how to access the values of these control when the user submits. Please help in this or suggest another approach Thanks

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• WPF drop shadow

  - by Petezah

  Currently I'm making something in WPF that has a border that contains a grid and other controls. The problem I'm facing is that whenever I set the Border.Effect property to a drop shadow effect every control contained in the border now has a drop shadow. Is there a way to set the shadow just to the border and not every control contained in the border? Here is a short example of my code: <Grid> <Border Margin="68,67,60,67" BorderBrush="Black" BorderThickness="1" CornerRadius="10"> <Border.Effect> <DropShadowEffect/> </Border.Effect> <Rectangle Fill="White" Stroke="Black" Margin="37,89,118,98" /> </Border> </Grid>

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• How to navigate from one view to other view using UIPageControl?

  - by Madan Mohan

  Hi Guys, I have page control but not navigating to other view. so please provide the solution. pageControl=[[UIPageControl alloc] initWithFrame:CGRectMake(0,380,320,40)]; pageControl.backgroundColor=[UIColor clearColor]; pageControl.userInteractionEnabled =YES; [pageControl addTarget:self action:@selector(pageAction:) forControlEvents:UIControlEventValueChanged]; [pageControl setHighlighted:YES]; -(void)pageAction:(UIPageControl*)control { [self displayNextPage]; [self displayPreviousPage]; } Thank You, Madan Mohan.

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• How to enable HTTP response caching in Spring Boot

  - by Samuli Kärkkäinen

  I have implemented a REST server using Spring Boot 1.0.2. I'm having trouble preventing Spring from setting HTTP headers that disable HTTP caching. My controller is as following: @Controller public class MyRestController { @RequestMapping(value = "/someUrl", method = RequestMethod.GET) public @ResponseBody ResponseEntity<String> myMethod( HttpServletResponse httpResponse) throws SQLException { return new ResponseEntity<String>("{}", HttpStatus.OK); } } All HTTP responses contain the following headers: Cache-Control: no-cache, no-store, max-age=0, must-revalidate Expires: 0 Pragma: no-cache I've tried the following to remove or change those headers: Call setCacheSeconds(-1) in the controller. Call httpResponse.setHeader("Cache-Control", "max-age=123") in the controller. Define @Bean that returns WebContentInterceptor for which I've called setCacheSeconds(-1). Set property spring.resources.cache-period to -1 or a positive value in application.properties. None of the above have had any effect. How do I disable or change these headers for all or individual requests in Spring Boot?

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• SQLPlus - spooling to multiple files from PL/SQL blocks

  - by FrustratedWithFormsDesigner

  I have a query that returns a lot of data into a CSV file. So much, in fact, that Excel can't open it - there are too many rows. Is there a way to control spool to spool to a new file everytime 65000 rows have been processed? Ideally, I'd like to have my output in files named in sequence, such as large_data_1.csv, large_data_2.csv, large_data_3.csv, etc... I could use dbms_output in a PL/SQL block to control how many rows are output, but then how would I switch files, as spool does not seem to be accessible from PL/SQL blocks? (Oracle 10g)

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• jQuery - datepicker - onblur

  - by d3020

  I'm using the jQuery datepicker where I have two textboxes (start date / end date). The user clicks in a respective textbox and the calendar shows up. That is OK. What I need to do is when the user say, clicks in the start date textbox and picks a date. I need an onblur event to be triggered then. Where do I set that onblur event for the calendar control after a date has been selected? I tried in the actual textbox but that's not right because that happens before an actual date is picked from the calendar control.

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• Element is already the child of another element.

  - by Erica

  I get the folowing error in my Silverlight application. But i cant figure out what control it is that is the problem. If i debug it don't break on anything in the code, it just fails in this framework callstack with only framework code. Is there any way to get more information on what part of a Silverlight app that is the problem in this case. Message: Sys.InvalidOperationException: ManagedRuntimeError error #4004 in control 'Xaml1': System.InvalidOperationException: Element is already the child of another element. at MS.Internal.XcpImports.CheckHResult(UInt32 hr) at MS.Internal.XcpImports.Collection_AddValue[T](PresentationFrameworkCollection1 collection, CValue value) at MS.Internal.XcpImports.Collection_AddDependencyObject[T](PresentationFrameworkCollection1 collection, DependencyObject value) at System.Windows.PresentationFrameworkCollection1.AddDependencyObject(DependencyObject value) at System.Windows.Controls.UIElementCollection.AddInternal(UIElement value) at System.Windows.PresentationFrameworkCollection1.Add(T value) at System.Windows.Controls.AutoCompleteBox.OnApplyTemplate() at System.Windows.FrameworkElement.OnApplyTemplate(IntPtr nativeTarget)

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• SphinxSearch or a spider - which one to choose?

  - by r2b2

  Hello, here is my problem: We own SiteA and SiteB and they share the same server and database where we have full control. SiteC , siteD and siteE are some of the sites we own as well but reside on a different web hosts. The goal is to create a unified search functionality for all of the sites mentioned above. That is if somebody search for a term in SiteA, the search result will automatically come up with results from SiteB,SiteC,SiteD and Site E too. The search results should be shown under the website they were found in. All these websites content are stored in their own databases. If I use SphinxSearch to index the above sites,I would then require those sites that we dont have complete control with to setup a web service where i can download a database dump or csv file for indexing. Im not quite sure about how a sphider will come into play here so need your opinion. Sphinx or a spider? THanks!

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• how to prevent MPMoviePlayer controls from hiding

  - by huevos de oro

  I am trying to implement a custom MPMoviePlayer to play mp3 audio. I have got it working in portrait mode along with an overlay window over the native controls - thanks to other stackoverflow posts. The current issue is the song progress control shows up when the media window opens (blue bar taking up the first 40 odd pixels), but seems to disappear when the song starts leaving a white bar. It will then re-appear when touching the area, so functionally works fine. I would like to find a way to ensure the controls always stay visible but have not found an appropriate property in the reference. Ideally I would like to have my custom control to replace the default, more because I would like to change the position that the look and feel. This being said, I understand it is not possible as the current position in the song from a MPMoviePlayer cannot be accessed.

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• Silverlight Chat WrapPanel Crash / Bug

  - by Matt

  I've been given the task to create a simple Silverlight chat box for two people. My control must adhere to the following requirements Scrollable Text must wrap if it's too long When a new item / message is added it must scroll that item into view Now I've successfully made a usercontrol to meet these requirements, but I've run into a possible bug / crash that I can't for the life of me fix. I'm looking for either a fix to the bug, or a different approach to creating a scrollable chat control. Here's the code I've been using. We'll start with my XAML for the chat window <ListBox x:Name="lbChatHistory" Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="2" ScrollViewer.VerticalScrollBarVisibility="Visible" ScrollViewer.HorizontalScrollBarVisibility="Disabled" > <ListBox.ItemTemplate> <DataTemplate> <Grid Background="Beige"> <Grid.ColumnDefinitions> <ColumnDefinition Width="70"></ColumnDefinition> <ColumnDefinition Width="Auto"></ColumnDefinition> </Grid.ColumnDefinitions> <TextBlock x:Name="lblPlayer" Foreground="{Binding ForeColor}" Text="{Binding Player}" Grid.Column="0"></TextBlock> <ContentPresenter Grid.Column="1" Width="200" Content="{Binding Message}" /> </Grid> </DataTemplate> </ListBox.ItemTemplate> </ListBox> The idea is to add a new Item to the listbox. The Item (as layed out in the XAML) is a simple 2 column grid. One column for the username, and one column for the message. Now the "items" that I add to the ListBox is a custom class. It has three properties (Player, ForeColor, and Message) that I using binding on within my XAML Player is a string of the current user to display. ForeColor is just a foreground color preference. It helps distinguish the difference between messages. Message is a WrapPanel. I programmatically break the supplied string on the white space for each word. Then for each word, I add a new TextBlock element to the WrapPanel Here is the custom class. public class ChatMessage :DependencyObject, INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; public static DependencyProperty PlayerProperty = DependencyProperty.Register( "Player", typeof( string ), typeof( ChatMessage ), new PropertyMetadata( new PropertyChangedCallback( OnPlayerPropertyChanged ) ) ); public static DependencyProperty MessageProperty = DependencyProperty.Register( "Message", typeof( WrapPanel ), typeof( ChatMessage ), new PropertyMetadata( new PropertyChangedCallback( OnMessagePropertyChanged ) ) ); public static DependencyProperty ForeColorProperty = DependencyProperty.Register( "ForeColor", typeof( SolidColorBrush ), typeof( ChatMessage ), new PropertyMetadata( new PropertyChangedCallback( OnForeColorPropertyChanged ) ) ); private static void OnForeColorPropertyChanged( DependencyObject d, DependencyPropertyChangedEventArgs e ) { ChatMessage c = d as ChatMessage; c.ForeColor = ( SolidColorBrush ) e.NewValue; } public ChatMessage() { Message = new WrapPanel(); ForeColor = new SolidColorBrush( Colors.White ); } private static void OnMessagePropertyChanged( DependencyObject d, DependencyPropertyChangedEventArgs e ) { ChatMessage c = d as ChatMessage; c.Message = ( WrapPanel ) e.NewValue; } private static void OnPlayerPropertyChanged( DependencyObject d, DependencyPropertyChangedEventArgs e ) { ChatMessage c = d as ChatMessage; c.Player = e.NewValue.ToString(); } public SolidColorBrush ForeColor { get { return ( SolidColorBrush ) GetValue( ForeColorProperty ); } set { SetValue( ForeColorProperty, value ); if(PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs( "ForeColor" )); } } public string Player { get { return ( string ) GetValue( PlayerProperty ); } set { SetValue( PlayerProperty, value ); if ( PropertyChanged != null ) PropertyChanged( this, new PropertyChangedEventArgs( "Player" ) ); } } public WrapPanel Message { get { return ( WrapPanel ) GetValue( MessageProperty ); } set { SetValue( MessageProperty, value ); if ( PropertyChanged != null ) PropertyChanged( this, new PropertyChangedEventArgs( "Message" ) ); } } } Lastly I add my items to the ListBox. Here's the simple method. It takes the above ChatMessage class as a parameter public void AddChatItem( ChatMessage msg ) { lbChatHistory.Items.Add( msg ); lbChatHistory.ScrollIntoView( msg ); } Now I've tested this and it all works. The problem I'm getting is when I use the scroll bar. You can scroll down using the side scroll bar or arrow keys, but when you scroll up Silverlight crashes. FireBug returns a ManagedRuntimeError #4004 with a XamlParseException. I'm soo close to having this control work, I can taste it! Any thoughts on what I should do or change? Is there a better approach than the one I've taken? Thanks in advance. UPDATE I've found an alternative solution using a ScrollViewer and an ItemsControl instead of a ListBox control. For the most part it's stable.

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• jQuery Select Menu Replacement

  - by Brad

  I have a select drop-down that selects a theme for the current page the user is on: <select id="style" name="acct-stylenum"> <option value="1" selected="true">Light</option> <option value="2">Dark</option> </select> Now what I would like to do is add two divs that will also control this select menu. I would much rather have the user select between two images than a select menu. The divs are as follows: <div class="style-box light"></div> <div class="style-box dark"></div> I would like to use jQuery to make the select menu hidden but still use its input. Also I would like the divs to control the menus value and show a selected state. Please let me know the easiest way this can be done using jQuery or JavaScript. Thanks in advance. -B

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• Howto bind a RoutedCommand in a child?

  - by Wouter

  I am having trouble binding a Command that is generated up the UI tree to a control. The following example illustrates my point, the CommandBinding in Grid does not act on the InputBindings in Window. Maybe I do not understand the point of commands, but I would like to have a nice solution for child controls to act on user input on the Window (any control on the Window). <Window x:Class="SilverFit.Menu.Wpf.WpfWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> <Window.InputBindings> <KeyBinding Command="Close" Key="Escape"/> <MouseBinding Command="Close" MouseAction="RightClick" /> </Window.InputBindings> <Grid Name="grid"> <Grid.CommandBindings> <CommandBinding Command="Close" Executed="Close"/> </Grid.CommandBindings> </Grid> </Window>

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• openvpn: after changing to server mode, client does not create TUN device

  - by lurscher

  i had a previously working configuration with the config files used in a previous question However, i've changed this now to the following configuration using server mode, everything on the logs seem fine, however the client doesn't create any tun interface, so i don't have anything to connect to, presumably, i need to add or push some route commands, but i don't have any idea at this point what i need to do. I am posting all my relevant configuration files server.conf: dev tun server 10.8.117.0 255.255.255.0 ifconfig-pool-persist ipp.txt tls-server dh /home/lurscher/keys/dh1024.pem ca /home/lurscher/keys/ca.crt cert /home/lurscher/keys/vpnCh8TestServer.crt key /home/lurscher/keys/vpnCh8TestServer.key status openvpn-status.log log openvpn.log comp-lzo verb 3 and client.conf: dev tun remote my.server.com tls-client ca /home/chuckq/keys/ca.crt cert /home/chuckq/keys/vpnCh8TestClient.crt key /home/chuckq/keys/vpnCh8TestClient.key ns-cert-type server ; port 1194 ; user nobody ; group nogroup status openvpn-status.log log openvpn.log comp-lzo verb 3 the server ifconfig shows a tun device: tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:10.8.117.1 P-t-P:10.8.117.2 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) However the client ifconfig does not show any tun interface! $ ifconfig tun0 tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 POINTOPOINT NOARP MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) the client log says: Tue May 17 23:27:09 2011 OpenVPN 2.1.0 i686-pc-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [MH] [PF_INET6] [eurephia] built on Jul 12 2010 Tue May 17 23:27:09 2011 IMPORTANT: OpenVPN's default port number is now 1194, based on an official port number assignment by IANA. OpenVPN 2.0-beta16 and earlier used 5000 as the default port. Tue May 17 23:27:09 2011 NOTE: the current --script-security setting may allow this configuration to call user-defined scripts Tue May 17 23:27:09 2011 /usr/bin/openssl-vulnkey -q -b 1024 -m <modulus omitted> Tue May 17 23:27:09 2011 LZO compression initialized Tue May 17 23:27:09 2011 Control Channel MTU parms [ L:1542 D:138 EF:38 EB:0 ET:0 EL:0 ] Tue May 17 23:27:09 2011 TUN/TAP device tun0 opened Tue May 17 23:27:09 2011 TUN/TAP TX queue length set to 100 Tue May 17 23:27:09 2011 Data Channel MTU parms [ L:1542 D:1450 EF:42 EB:135 ET:0 EL:0 AF:3/1 ] Tue May 17 23:27:09 2011 Local Options hash (VER=V4): '41690919' Tue May 17 23:27:09 2011 Expected Remote Options hash (VER=V4): '530fdded' Tue May 17 23:27:09 2011 Socket Buffers: R=[114688->131072] S=[114688->131072] Tue May 17 23:27:09 2011 UDPv4 link local (bound): [undef] Tue May 17 23:27:09 2011 UDPv4 link remote: [AF_INET]192.168.0.101:1194 Tue May 17 23:27:09 2011 TLS: Initial packet from [AF_INET]192.168.0.101:1194, sid=8e8bdc33 f4275407 Tue May 17 23:27:09 2011 VERIFY OK: depth=1, /C=CA/ST=Out/L=There/O=Ubuntu/OU=Home/CN=Ubuntu_CA/name=lurscher/[email protected] Tue May 17 23:27:09 2011 VERIFY OK: nsCertType=SERVER Tue May 17 23:27:09 2011 VERIFY OK: depth=0, /C=CA/ST=Out/L=There/O=Ubuntu/OU=Home/CN=vpnCh8TestServer/name=lurscher/[email protected] Tue May 17 23:27:09 2011 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key Tue May 17 23:27:09 2011 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Tue May 17 23:27:09 2011 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key Tue May 17 23:27:09 2011 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Tue May 17 23:27:09 2011 Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 1024 bit RSA Tue May 17 23:27:09 2011 [vpnCh8TestServer] Peer Connection Initiated with [AF_INET]192.168.0.101:1194 Tue May 17 23:27:10 2011 Initialization Sequence Completed the client status log: OpenVPN STATISTICS Updated,Tue May 17 23:30:09 2011 TUN/TAP read bytes,0 TUN/TAP write bytes,0 TCP/UDP read bytes,5604 TCP/UDP write bytes,4244 Auth read bytes,0 pre-compress bytes,0 post-compress bytes,0 pre-decompress bytes,0 post-decompress bytes,0 END and the server log says: Tue May 17 23:18:25 2011 OpenVPN 2.1.0 x86_64-pc-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [MH] [PF_INET6] [eurephia] built on Jul 12 2010 Tue May 17 23:18:25 2011 IMPORTANT: OpenVPN's default port number is now 1194, based on an official port number assignment by IANA. OpenVPN 2.0-beta16 and earlier used 5000 as the default port. Tue May 17 23:18:25 2011 WARNING: --keepalive option is missing from server config Tue May 17 23:18:25 2011 NOTE: your local LAN uses the extremely common subnet address 192.168.0.x or 192.168.1.x. Be aware that this might create routing conflicts if you connect to the VPN server from public locations such as internet cafes that use the same subnet. Tue May 17 23:18:25 2011 NOTE: the current --script-security setting may allow this configuration to call user-defined scripts Tue May 17 23:18:25 2011 Diffie-Hellman initialized with 1024 bit key Tue May 17 23:18:25 2011 /usr/bin/openssl-vulnkey -q -b 1024 -m <modulus omitted> Tue May 17 23:18:25 2011 TLS-Auth MTU parms [ L:1542 D:138 EF:38 EB:0 ET:0 EL:0 ] Tue May 17 23:18:25 2011 ROUTE default_gateway=192.168.0.1 Tue May 17 23:18:25 2011 TUN/TAP device tun0 opened Tue May 17 23:18:25 2011 TUN/TAP TX queue length set to 100 Tue May 17 23:18:25 2011 /sbin/ifconfig tun0 10.8.117.1 pointopoint 10.8.117.2 mtu 1500 Tue May 17 23:18:25 2011 /sbin/route add -net 10.8.117.0 netmask 255.255.255.0 gw 10.8.117.2 Tue May 17 23:18:25 2011 Data Channel MTU parms [ L:1542 D:1450 EF:42 EB:135 ET:0 EL:0 AF:3/1 ] Tue May 17 23:18:25 2011 Socket Buffers: R=[126976->131072] S=[126976->131072] Tue May 17 23:18:25 2011 UDPv4 link local (bound): [undef] Tue May 17 23:18:25 2011 UDPv4 link remote: [undef] Tue May 17 23:18:25 2011 MULTI: multi_init called, r=256 v=256 Tue May 17 23:18:25 2011 IFCONFIG POOL: base=10.8.117.4 size=62 Tue May 17 23:18:25 2011 IFCONFIG POOL LIST Tue May 17 23:18:25 2011 vpnCh8TestClient,10.8.117.4 Tue May 17 23:18:25 2011 Initialization Sequence Completed Tue May 17 23:27:22 2011 MULTI: multi_create_instance called Tue May 17 23:27:22 2011 192.168.0.104:1194 Re-using SSL/TLS context Tue May 17 23:27:22 2011 192.168.0.104:1194 LZO compression initialized Tue May 17 23:27:22 2011 192.168.0.104:1194 Control Channel MTU parms [ L:1542 D:138 EF:38 EB:0 ET:0 EL:0 ] Tue May 17 23:27:22 2011 192.168.0.104:1194 Data Channel MTU parms [ L:1542 D:1450 EF:42 EB:135 ET:0 EL:0 AF:3/1 ] Tue May 17 23:27:22 2011 192.168.0.104:1194 Local Options hash (VER=V4): '530fdded' Tue May 17 23:27:22 2011 192.168.0.104:1194 Expected Remote Options hash (VER=V4): '41690919' Tue May 17 23:27:22 2011 192.168.0.104:1194 TLS: Initial packet from [AF_INET]192.168.0.104:1194, sid=8972b565 79323f68 Tue May 17 23:27:22 2011 192.168.0.104:1194 VERIFY OK: depth=1, /C=CA/ST=Out/L=There/O=Ubuntu/OU=Home/CN=Ubuntu_CA/name=lurscher/[email protected] Tue May 17 23:27:22 2011 192.168.0.104:1194 VERIFY OK: depth=0, /C=CA/ST=Out/L=There/O=Ubuntu/OU=Home/CN=Ubuntu_CA/name=lurscher/[email protected] Tue May 17 23:27:22 2011 192.168.0.104:1194 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key Tue May 17 23:27:22 2011 192.168.0.104:1194 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Tue May 17 23:27:22 2011 192.168.0.104:1194 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key Tue May 17 23:27:22 2011 192.168.0.104:1194 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Tue May 17 23:27:22 2011 192.168.0.104:1194 Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 1024 bit RSA Tue May 17 23:27:22 2011 192.168.0.104:1194 [vpnCh8TestClient] Peer Connection Initiated with [AF_INET]192.168.0.104:1194 Tue May 17 23:27:22 2011 vpnCh8TestClient/192.168.0.104:1194 MULTI: Learn: 10.8.117.6 -> vpnCh8TestClient/192.168.0.104:1194 Tue May 17 23:27:22 2011 vpnCh8TestClient/192.168.0.104:1194 MULTI: primary virtual IP for vpnCh8TestClient/192.168.0.104:1194: 10.8.117.6 finally, the server status log: OpenVPN CLIENT LIST Updated,Tue May 17 23:36:25 2011 Common Name,Real Address,Bytes Received,Bytes Sent,Connected Since vpnCh8TestClient,192.168.0.104:1194,4244,5604,Tue May 17 23:27:22 2011 ROUTING TABLE Virtual Address,Common Name,Real Address,Last Ref 10.8.117.6,vpnCh8TestClient,192.168.0.104:1194,Tue May 17 23:27:22 2011 GLOBAL STATS Max bcast/mcast queue length,0 END

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• First toe in the water with Object Databases : DB4O

  - by REA_ANDREW

  I have been wanting to have a play with Object Databases for a while now, and today I have done just that.  One of the obvious choices I had to make was which one to use.  My criteria for choosing one today was simple, I wanted one which I could literally wack in and start using, which means I wanted one which either had a .NET API or was designed/ported to .NET.  My decision was between two being: db4o MongoDb I went for db4o for the single reason that it looked like I could get it running and integrated the quickest.  I am making a Blogging application and front end as a project with which I can test and learn with these object databases.  Another requirement which I thought I would mention is that I also want to be able to use the said database in a shared hosting environment where I cannot install, run and maintain a server instance of said object database.  I can do exactly this with db4o. I have not tried to do this with MongoDb at time of writing.  There are quite a few in the industry now and you read an interesting post about different ones and how they are used with some of the heavy weights in the industry here : http://blog.marcua.net/post/442594842/notes-from-nosql-live-boston-2010 In the example which I am building I am using StructureMap as my IOC.  To inject the object for db4o I went with a Singleton instance scope as I am using a single file and I need this to be available to any thread on in the process as opposed to using the server implementation where I could open and close client connections with the server handling each one respectively.  Again I want to point out that I have chosen to stick with the non server implementation of db4o as I wanted to use this in a shared hosting environment where I cannot have such servers installed and run.     public static class Bootstrapper    {        public static void ConfigureStructureMap()        {            ObjectFactory.Initialize(x => x.AddRegistry(new MyApplicationRegistry()));        }    }    public class MyApplicationRegistry : Registry    {        public const string DB4O_FILENAME = "blog123";        public string DbPath        {            get            {                return Path.Combine(Path.GetDirectoryName(Assembly.GetAssembly(typeof(IBlogRepository)).Location), DB4O_FILENAME);            }        }        public MyApplicationRegistry()        {            For<IObjectContainer>().Singleton().Use(                () => Db4oEmbedded.OpenFile(Db4oEmbedded.NewConfiguration(), DbPath));            Scan(assemblyScanner =>            {                assemblyScanner.TheCallingAssembly();                assemblyScanner.WithDefaultConventions();            });        }    } So my code above is the structure map plumbing which I use for the application.  I am doing this simply as a quick scratch pad to play around with different things so I am simply segregating logical layers with folder structure as opposed to different assemblies.  It will be easy if I want to do this with any segment but for the purposes of example I have literally just wacked everything in the one assembly.  You can see an example file structure I have on the right.  I am planning on testing out a few implementations of the object databases out there so I can program to an interface of IBlogRepository One of the things which I was unsure about was how it performed under a multi threaded environment which it will undoubtedly be used 9 times out of 10, and for the reason that I am using the db context as a singleton, I assumed that the library was of course thread safe but I did not know as I have not read any where in the documentation, again this is probably me not reading things correctly.  In short though I threw together a simple test where I simply iterate to a limit each time kicking a common task off with a thread from a thread pool.  This task simply created and added an random Post and added it to the storage. The execution of the threads I put inside the Setup of the Test and then simply ensure the number of posts committed to the database is equal to the number of iterations I made; here is the code I used to do the multi thread jobs: [TestInitialize] public void Setup() { var sw = new System.Diagnostics.Stopwatch(); sw.Start(); var resetEvent = new ManualResetEvent(false); ThreadPool.SetMaxThreads(20, 20); for (var i = 0; i < MAX_ITERATIONS; i++) { ThreadPool.QueueUserWorkItem(delegate(object state) { var eventToReset = (ManualResetEvent)state; var post = new Post { Author = MockUser, Content = "Mock Content", Title = "Title" }; Repository.Put(post); var counter = Interlocked.Decrement(ref _threadCounter); if (counter == 0) eventToReset.Set(); }, resetEvent); } WaitHandle.WaitAll(new[] { resetEvent }); sw.Stop(); Console.WriteLine("{0:00}.{1:00} seconds", sw.Elapsed.Seconds, sw.Elapsed.Milliseconds); }   I was not doing this to test out the speed performance of db4o but while I was doing this I could not help but put in a StopWatch and see out of sheer interest how fast it would take to insert a number of Posts.  I tested it out in this case with 10000 inserts of a small, simple POCO and it resulted in an average of:  899.36 object inserts / second.  Again this is just  simple crude test which came out of my curiosity at how it performed under many threads when using the non server implementation of db4o. The spec summary of the computer I used is as follows: With regards to the actual Repository implementation itself, it really is quite straight forward and I have to say I am very surprised at how easy it was to integrate and get up and running.  One thing I have noticed in the exposure I have had so far is that the Query returns IList<T> as opposed to IQueryable<T> but again I have not looked into this in depth and this could be there already and if not they have provided everything one needs to make there own repository.  An example of a couple of methods from by db4o implementation of the BlogRepository is below: public class BlogRepository : IBlogRepository { private readonly IObjectContainer _db; public BlogRepository(IObjectContainer db) { _db = db; } public void Put(DomainObject obj) { _db.Store(obj); } public void Delete(DomainObject obj) { _db.Delete(obj); } public Post GetByKey(object key) { return _db.Query<Post>(post => post.Key == key).FirstOrDefault(); } … Anyways I hope to get a few more implementations going of the object databases and literally just get familiarized with them and the concept of no sql databases. Cheers for now, Andrew

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• VB.NET - 'Title' is not a member of 'Calendar.Appointment'

  - by Daniel

  I am having a problem with my code. I am using VB.NET and Visual Studio 2010 to write my program. The source of the control that I am using can be found here. First, I imported the Calendar.DayView.dll file into my toolbox to use as a control. Then I added the following code to my existing code: Private Sub DayView1_NewAppointment(ByVal sender As System.Object, ByVal args As Calendar.NewAppointmentEventArgs) Dim appointment As New Calendar.Appointment() appointment.StartDate = args.StartDate appointment.EndDate = args.EndDate appointment.Title = args.Title appointments.Add(appointment) End Sub I get this error 'Title' is not a member of 'Calendar.Appointment'. I have no access to the Calendar namespace or the Appointment class. I am able to view the properties of both in the Object Browser but I can't edit any of them. Any suggestions?

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• Modal MessageBox for ASP.NET without jQuery

  - by Joe

  I have an assembly with custom ASP.NET server controls that is used in several, mostly in-house, ASP.NET 2.0 applications. The server controls use simple modal popup messageboxes, which are currently implemented using the javascript alert and confirm functions. I want to release a new version of this assembly that uses a better solution for messageboxes, including support for Yes/No buttons. The appearance would be something like a simplified version of the Ajax Control Toolkit ModalPopup extender (sample here). My constraints are that this should be as easy as possible to integrate into existing ASP.NET 2.0 applications without introducing new dependencies: ideally just drop in a new version of the assembly, that contains all the javascript it needs as an embedded resource, and possibly a CSS file. Because of this constraint, I am not considering solutions I've seen that use jquery, or the ASP.NET Ajax Control Toolkit, which appears to require adding elements to pages that use the extenders (ScriptManagers and the like). Any recommendations?

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• How to Prevent SelectionChange a Silverlight DataGrid

  - by Matt Eland

  I'm using a Silverlight 3 DataGrid control and have set the SelectionMode to Extended. The DataGrid takes care of managing the extended selection for me in an almost perfect manner out of the box, but a key piece of the logic is interfering with me. I have a cell that can function as a drag and drop thumb and initiate a drag operation but users want to do a series of shift or control clicks to set a selection followed by a click and drag on one of the selected rows to initiate the drag. The problem is that the click and drag at the end of this series causes the selection to be set to only the row that was clicked. I've poked around for ways of conditionally preventing the DataGrid from changing selection, but can't seem to find anything that works. Does anyone have any ideas for preventing selection from changing?

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• "Z-Index" in winforms

  - by sv88erik

  In CSS, we have a Property called z-index, what is the same in Winfrom set for a Panel control to the "Z-Index?

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• How do you debug a XamlParseException?

  - by Craig Shearer

  I'm trying to use a 3rd party component in my Silverlight application and when I try to create an instance of the control, I get a XamlParseException: {System.Windows.Markup.XamlParseException: Set property 'System.Windows.FrameworkElement.Style' threw an exception. [Line: 0 Position: 0] --- System.Windows.Markup.XamlParseException: Elements in the same ResourceDictionary cannot have the same x:Key [Line: 1739 Position: 47] at MS.Internal.XcpImports.CreateFromXaml(UnmanagedMemoryStream stream, String sourceAssemblyName, Boolean createNamescope, Boolean requireDefaultNamespace, Boolean allowEventHandlers) at System.Windows.Controls.Control.GetBuiltInStyle(IntPtr nativeTarget, IntPtr& nativeStyle) --- End of inner exception stack trace --- at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator) at SpellCheckerSample.StandardSpellDialog.InitializeComponent() at SpellCheckerSample.StandardSpellDialog..ctor()} How can I debug this? How do I know what file line 1739, Position 47 is in?

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• MVC Automatic Menu

  - by Nuri Halperin

  An ex-colleague of mine used to call his SQL script generator "Super-Scriptmatic 2000". It impressed our then boss little, but was fun to say and use. We called every batch job and script "something 2000" from that day on. I'm tempted to call this one Menu-Matic 2000, except it's waaaay past 2000. Oh well. The problem: I'm developing a bunch of stuff in MVC. There's no PM to generate mounds of requirements and there's no Ux Architect to create wireframe. During development, things change. Specifically, actions get renamed, moved from controller x to y etc. Well, as the site grows, it becomes a major pain to keep a static menu up to date, because the links change. The HtmlHelper doesn't live up to it's name and provides little help. How do I keep this growing list of pesky little forgotten actions reigned in? The general plan is: Decorate every action you want as a menu item with a custom attribute Reflect out all menu items into a structure at load time Render the menu using as CSS  friendly <ul><li> HTML. The MvcMenuItemAttribute decorates an action, designating it to be included as a menu item: [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)] public class MvcMenuItemAttribute : Attribute {   public string MenuText { get; set; }   public int Order { get; set; }   public string ParentLink { get; set; }   internal string Controller { get; set; }   internal string Action { get; set; }     #region ctor   public MvcMenuItemAttribute(string menuText) : this(menuText, 0) { } public MvcMenuItemAttribute(string menuText, int order) { MenuText = menuText; Order = order; }       internal string Link { get { return string.Format("/{0}/{1}", Controller, this.Action); } }   internal MvcMenuItemAttribute ParentItem { get; set; } #endregion } The MenuText allows overriding the text displayed on the menu. The Order allows the items to be ordered. The ParentLink allows you to make this item a child of another menu item. An example action could then be decorated thusly: [MvcMenuItem("Tracks", Order = 20, ParentLink = "/Session/Index")] . All pretty straightforward methinks. The challenge with menu hierarchy becomes fairly apparent when you try to render a menu and highlight the "current" item or render a breadcrumb control. Both encounter an  ambiguity if you allow a data source to have more than one menu item with the same URL link. The issue is that there is no great way to tell which link a person click. Using referring URL will fail if a user bookmarked the page. Using some extra query string to disambiguate duplicate URLs essentially changes the links, and also ads a chance of collision with other query parameters. Besides, that smells. The stock ASP.Net sitemap provider simply disallows duplicate URLS. I decided not to, and simply pick the first one encountered as the "current". Although it doesn't solve the issue completely – one might say they wanted the second of the 2 links to be "current"- it allows one to include a link twice (home->deals and products->deals etc), and the logic of deciding "current" is easy enough to explain to the customer. Now that we got that out of the way, let's build the menu data structure: public static List<MvcMenuItemAttribute> ListMenuItems(Assembly assembly) { var result = new List<MvcMenuItemAttribute>(); foreach (var type in assembly.GetTypes()) { if (!type.IsSubclassOf(typeof(Controller))) { continue; } foreach (var method in type.GetMethods()) { var items = method.GetCustomAttributes(typeof(MvcMenuItemAttribute), false) as MvcMenuItemAttribute[]; if (items == null) { continue; } foreach (var item in items) { if (String.IsNullOrEmpty(item.Controller)) { item.Controller = type.Name.Substring(0, type.Name.Length - "Controller".Length); } if (String.IsNullOrEmpty(item.Action)) { item.Action = method.Name; } result.Add(item); } } } return result.OrderBy(i => i.Order).ToList(); } Using reflection, the ListMenuItems method takes an assembly (you will hand it your MVC web assembly) and generates a list of menu items. It digs up all the types, and for each one that is an MVC Controller, digs up the methods. Methods decorated with the MvcMenuItemAttribute get plucked and added to the output list. Again, pretty simple. To make the structure hierarchical, a LINQ expression matches up all the items to their parent: public static void RegisterMenuItems(List<MvcMenuItemAttribute> items) { _MenuItems = items; _MenuItems.ForEach(i => i.ParentItem = items.FirstOrDefault(p => String.Equals(p.Link, i.ParentLink, StringComparison.InvariantCultureIgnoreCase))); } The _MenuItems is simply an internal list to keep things around for later rendering. Finally, to package the menu building for easy consumption: public static void RegisterMenuItems(Type mvcApplicationType) { RegisterMenuItems(ListMenuItems(Assembly.GetAssembly(mvcApplicationType))); } To bring this puppy home, a call in Global.asax.cs Application_Start() registers the menu. Notice the ugliness of reflection is tucked away from the innocent developer. All they have to do is call the RegisterMenuItems() and pass in the type of the application. When you use the new project template, global.asax declares a class public class MvcApplication : HttpApplication and that is why the Register call passes in that type. protected void Application_Start() { AreaRegistration.RegisterAllAreas(); RegisterRoutes(RouteTable.Routes);   MvcMenu.RegisterMenuItems(typeof(MvcApplication)); }   What else is left to do? Oh, right, render! public static void ShowMenu(this TextWriter output) { var writer = new HtmlTextWriter(output);   renderHierarchy(writer, _MenuItems, null); }   public static void ShowBreadCrumb(this TextWriter output, Uri currentUri) { var writer = new HtmlTextWriter(output); string currentLink = "/" + currentUri.GetComponents(UriComponents.Path, UriFormat.Unescaped);   var menuItem = _MenuItems.FirstOrDefault(m => m.Link.Equals(currentLink, StringComparison.CurrentCultureIgnoreCase)); if (menuItem != null) { renderBreadCrumb(writer, _MenuItems, menuItem); } }   private static void renderBreadCrumb(HtmlTextWriter writer, List<MvcMenuItemAttribute> menuItems, MvcMenuItemAttribute current) { if (current == null) { return; } var parent = current.ParentItem; renderBreadCrumb(writer, menuItems, parent); writer.Write(current.MenuText); writer.Write(" / ");   }     static void renderHierarchy(HtmlTextWriter writer, List<MvcMenuItemAttribute> hierarchy, MvcMenuItemAttribute root) { if (!hierarchy.Any(i => i.ParentItem == root)) return;   writer.RenderBeginTag(HtmlTextWriterTag.Ul); foreach (var current in hierarchy.Where(element => element.ParentItem == root).OrderBy(i => i.Order)) { if (ItemFilter == null || ItemFilter(current)) {   writer.RenderBeginTag(HtmlTextWriterTag.Li); writer.AddAttribute(HtmlTextWriterAttribute.Href, current.Link); writer.AddAttribute(HtmlTextWriterAttribute.Alt, current.MenuText); writer.RenderBeginTag(HtmlTextWriterTag.A); writer.WriteEncodedText(current.MenuText); writer.RenderEndTag(); // link renderHierarchy(writer, hierarchy, current); writer.RenderEndTag(); // li } } writer.RenderEndTag(); // ul } The ShowMenu method renders the menu out to the provided TextWriter. In previous posts I've discussed my partiality to using well debugged, time test HtmlTextWriter to render HTML rather than writing out angled brackets by hand. In addition, writing out using the actual writer on the actual stream rather than generating string and byte intermediaries (yes, StringBuilder being no exception) disturbs me. To carry out the rendering of an hierarchical menu, the recursive renderHierarchy() is used. You may notice that an ItemFilter is called before rendering each item. I figured that at some point one might want to exclude certain items from the menu based on security role or context or something. That delegate is the hook for such future feature. To carry out rendering of a breadcrumb recursion is used again, this time simply to unwind the parent hierarchy from the leaf node, then rendering on the return from the recursion rather than as we go along deeper. I guess I was stuck in LISP that day.. recursion is fun though.   Now all that is left is some usage! Open your Site.Master or wherever you'd like to place a menu or breadcrumb, and plant one of these calls: <% MvcMenu.ShowBreadCrumb(this.Writer, Request.Url); %> to show a breadcrumb trail (notice lack of "=" after <% and the semicolon). <% MvcMenu.ShowMenu(Writer); %> to show the menu.   As mentioned before, the HTML output is nested <UL> <LI> tags, which should make it easy to style using abundant CSS to produce anything from static horizontal or vertical to dynamic drop-downs.   This has been quite a fun little implementation and I was pleased that the code size remained low. The main crux was figuring out how to pass parent information from the attribute to the hierarchy builder because attributes have restricted parameter types. Once I settled on that implementation, the rest falls into place quite easily.

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• Freeze the indent of a row group in DevExpress GridControl

  - by brader

  I am required to display a DevExpress WinForms GridControl where the rows must be grouped by a date column. When horizontally scrolling the grid, I am required to keep the group row and group indents fixed to the left of the control (so they do not scroll with the columns). I have so far been unable to find any built-in capability for this. There is the ability to fix a column to the left or right side of the control, but the indent is not a true column. FYI, the group row portion is staying "fixed" by handling the drawing of it to always position it at the left. I do not see a way of controlling the drawing of the indent however. Attempts to custom draw an indent have been unsuccessful so far. We are using version 9.3.2.0 of the DevExpress XtraGrid controls for WinForms. Does anyone have any solutions or workarounds that might allow us to at least give the appearance that the group indents are fixed? Thank you!

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• How to detect touches on MPMoviePlayerController window and still having the standard playback cont

  - by gkedmi

  Hello I have the MPMoviePlayerController set up to play a movie.I want to detect a touch on the movie for bringing up few buttons.I used the code : // The movie's window is the one that is active UIWindow* moviePlayerWindow = [[UIApplication sharedApplication] keyWindow]; // Now we create an invisible control with the same size as the window UIControl* overlay = [[[UIControl alloc] initWithFrame:moviePlayerWindow.frame]autorelease]; // We want to get notified whenever the overlay control is touched [overlay addTarget:self action:@selector(movieWindowTouched:) forControlEvents:UIControlEventTouchDown]; // Add the overlay to the window's subviews [moviePlayerWindow addSubview:overlay]; but then the play back controllers doesn't appear , I guess because the player window doesn't get the touch.how can I keep the player controllers and still detects touches? thanks

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• Are there alternatives to UltraWinGrid (for C#)?

  - by MPelletier

  I've been using the Infragistics UltraWinGrid for a while in a C# project, and while it's very spiffy, it is sometimes a bit heavy to run (and editing it in Visual Studio can be hazardous). I'm looking for a lighter alternative. Looks (always a big plus with Infragistics) are not as important as functionality. Namely, I'm looking for a beefed up DataGridView which: has data binding (duh!) has lock control over editing allows for sub-tables on opening a row can have multiple headers to group columns together (say header 1 is composed of "Group A" and "Group B", and header 2 has various columns under each group) has sorting by column (and can sort numbers properly, even if it does not have a stock method at first) has filtering by column (perhaps the most demanding spec) à la UltraWinGrid/Excel (text field with a way to specify if the filter is equal, not equal, greater, lesser, starts with, ends with, etc). supports check box, text box or data bound list/combo box cells allows cells to be merged (not the control cells of course!) can have events bound to each row (say double click)

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• Execute Silverlight 4 Command on Load

  - by Craig Shoemaker

  How do you implement a Silverlight 4 command to execute when the user control loads instead of being mapped to an explicit button click?

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• Hello Operator, My Switch Is Bored

  - by Paul White

  This is a post for T-SQL Tuesday #43 hosted by my good friend Rob Farley. The topic this month is Plan Operators. I haven’t taken part in T-SQL Tuesday before, but I do like to write about execution plans, so this seemed like a good time to start. This post is in two parts. The first part is primarily an excuse to use a pretty bad play on words in the title of this blog post (if you’re too young to know what a telephone operator or a switchboard is, I hate you). The second part of the post looks at an invisible query plan operator (so to speak). 1. My Switch Is Bored Allow me to present the rare and interesting execution plan operator, Switch: Books Online has this to say about Switch: Following that description, I had a go at producing a Fast Forward Cursor plan that used the TOP operator, but had no luck. That may be due to my lack of skill with cursors, I’m not too sure. The only application of Switch in SQL Server 2012 that I am familiar with requires a local partitioned view: CREATE TABLE dbo.T1 (c1 int NOT NULL CHECK (c1 BETWEEN 00 AND 24)); CREATE TABLE dbo.T2 (c1 int NOT NULL CHECK (c1 BETWEEN 25 AND 49)); CREATE TABLE dbo.T3 (c1 int NOT NULL CHECK (c1 BETWEEN 50 AND 74)); CREATE TABLE dbo.T4 (c1 int NOT NULL CHECK (c1 BETWEEN 75 AND 99)); GO CREATE VIEW V1 AS SELECT c1 FROM dbo.T1 UNION ALL SELECT c1 FROM dbo.T2 UNION ALL SELECT c1 FROM dbo.T3 UNION ALL SELECT c1 FROM dbo.T4; Not only that, but it needs an updatable local partitioned view. We’ll need some primary keys to meet that requirement: ALTER TABLE dbo.T1 ADD CONSTRAINT PK_T1 PRIMARY KEY (c1);   ALTER TABLE dbo.T2 ADD CONSTRAINT PK_T2 PRIMARY KEY (c1);   ALTER TABLE dbo.T3 ADD CONSTRAINT PK_T3 PRIMARY KEY (c1);   ALTER TABLE dbo.T4 ADD CONSTRAINT PK_T4 PRIMARY KEY (c1); We also need an INSERT statement that references the view. Even more specifically, to see a Switch operator, we need to perform a single-row insert (multi-row inserts use a different plan shape): INSERT dbo.V1 (c1) VALUES (1); And now…the execution plan: The Constant Scan manufactures a single row with no columns. The Compute Scalar works out which partition of the view the new value should go in. The Assert checks that the computed partition number is not null (if it is, an error is returned). The Nested Loops Join executes exactly once, with the partition id as an outer reference (correlated parameter). The Switch operator checks the value of the parameter and executes the corresponding input only. If the partition id is 0, the uppermost Clustered Index Insert is executed, adding a row to table T1. If the partition id is 1, the next lower Clustered Index Insert is executed, adding a row to table T2…and so on. In case you were wondering, here’s a query and execution plan for a multi-row insert to the view: INSERT dbo.V1 (c1) VALUES (1), (2); Yuck! An Eager Table Spool and four Filters! I prefer the Switch plan. My guess is that almost all the old strategies that used a Switch operator have been replaced over time, using things like a regular Concatenation Union All combined with Start-Up Filters on its inputs. Other new (relative to the Switch operator) features like table partitioning have specific execution plan support that doesn’t need the Switch operator either. This feels like a bit of a shame, but perhaps it is just nostalgia on my part, it’s hard to know. Please do let me know if you encounter a query that can still use the Switch operator in 2012 – it must be very bored if this is the only possible modern usage! 2. Invisible Plan Operators The second part of this post uses an example based on a question Dave Ballantyne asked using the SQL Sentry Plan Explorer plan upload facility. If you haven’t tried that yet, make sure you’re on the latest version of the (free) Plan Explorer software, and then click the Post to SQLPerformance.com button. That will create a site question with the query plan attached (which can be anonymized if the plan contains sensitive information). Aaron Bertrand and I keep a close eye on questions there, so if you have ever wanted to ask a query plan question of either of us, that’s a good way to do it. The problem The issue I want to talk about revolves around a query issued against a calendar table. The script below creates a simplified version and adds 100 years of per-day information to it: USE tempdb; GO CREATE TABLE dbo.Calendar ( dt date NOT NULL, isWeekday bit NOT NULL, theYear smallint NOT NULL,   CONSTRAINT PK__dbo_Calendar_dt PRIMARY KEY CLUSTERED (dt) ); GO -- Monday is the first day of the week for me SET DATEFIRST 1;   -- Add 100 years of data INSERT dbo.Calendar WITH (TABLOCKX) (dt, isWeekday, theYear) SELECT CA.dt, isWeekday = CASE WHEN DATEPART(WEEKDAY, CA.dt) IN (6, 7) THEN 0 ELSE 1 END, theYear = YEAR(CA.dt) FROM Sandpit.dbo.Numbers AS N CROSS APPLY ( VALUES (DATEADD(DAY, N.n - 1, CONVERT(date, '01 Jan 2000', 113))) ) AS CA (dt) WHERE N.n BETWEEN 1 AND 36525; The following query counts the number of weekend days in 2013: SELECT Days = COUNT_BIG(*) FROM dbo.Calendar AS C WHERE theYear = 2013 AND isWeekday = 0; It returns the correct result (104) using the following execution plan: The query optimizer has managed to estimate the number of rows returned from the table exactly, based purely on the default statistics created separately on the two columns referenced in the query’s WHERE clause. (Well, almost exactly, the unrounded estimate is 104.289 rows.) There is already an invisible operator in this query plan – a Filter operator used to apply the WHERE clause predicates. We can see it by re-running the query with the enormously useful (but undocumented) trace flag 9130 enabled: Now we can see the full picture. The whole table is scanned, returning all 36,525 rows, before the Filter narrows that down to just the 104 we want. Without the trace flag, the Filter is incorporated in the Clustered Index Scan as a residual predicate. It is a little bit more efficient than using a separate operator, but residual predicates are still something you will want to avoid where possible. The estimates are still spot on though: Anyway, looking to improve the performance of this query, Dave added the following filtered index to the Calendar table: CREATE NONCLUSTERED INDEX Weekends ON dbo.Calendar(theYear) WHERE isWeekday = 0; The original query now produces a much more efficient plan: Unfortunately, the estimated number of rows produced by the seek is now wrong (365 instead of 104): What’s going on? The estimate was spot on before we added the index! Explanation You might want to grab a coffee for this bit. Using another trace flag or two (8606 and 8612) we can see that the cardinality estimates were exactly right initially: The highlighted information shows the initial cardinality estimates for the base table (36,525 rows), the result of applying the two relational selects in our WHERE clause (104 rows), and after performing the COUNT_BIG(*) group by aggregate (1 row). All of these are correct, but that was before cost-based optimization got involved :) Cost-based optimization When cost-based optimization starts up, the logical tree above is copied into a structure (the ‘memo’) that has one group per logical operation (roughly speaking). The logical read of the base table (LogOp_Get) ends up in group 7; the two predicates (LogOp_Select) end up in group 8 (with the details of the selections in subgroups 0-6). These two groups still have the correct cardinalities as trace flag 8608 output (initial memo contents) shows: During cost-based optimization, a rule called SelToIdxStrategy runs on group 8. It’s job is to match logical selections to indexable expressions (SARGs). It successfully matches the selections (theYear = 2013, is Weekday = 0) to the filtered index, and writes a new alternative into the memo structure. The new alternative is entered into group 8 as option 1 (option 0 was the original LogOp_Select): The new alternative is to do nothing (PhyOp_NOP = no operation), but to instead follow the new logical instructions listed below the NOP. The LogOp_GetIdx (full read of an index) goes into group 21, and the LogOp_SelectIdx (selection on an index) is placed in group 22, operating on the result of group 21. The definition of the comparison ‘the Year = 2013’ (ScaOp_Comp downwards) was already present in the memo starting at group 2, so no new memo groups are created for that. New Cardinality Estimates The new memo groups require two new cardinality estimates to be derived. First, LogOp_Idx (full read of the index) gets a predicted cardinality of 10,436. This number comes from the filtered index statistics: DBCC SHOW_STATISTICS (Calendar, Weekends) WITH STAT_HEADER; The second new cardinality derivation is for the LogOp_SelectIdx applying the predicate (theYear = 2013). To get a number for this, the cardinality estimator uses statistics for the column ‘theYear’, producing an estimate of 365 rows (there are 365 days in 2013!): DBCC SHOW_STATISTICS (Calendar, theYear) WITH HISTOGRAM; This is where the mistake happens. Cardinality estimation should have used the filtered index statistics here, to get an estimate of 104 rows: DBCC SHOW_STATISTICS (Calendar, Weekends) WITH HISTOGRAM; Unfortunately, the logic has lost sight of the link between the read of the filtered index (LogOp_GetIdx) in group 22, and the selection on that index (LogOp_SelectIdx) that it is deriving a cardinality estimate for, in group 21. The correct cardinality estimate (104 rows) is still present in the memo, attached to group 8, but that group now has a PhyOp_NOP implementation. Skipping over the rest of cost-based optimization (in a belated attempt at brevity) we can see the optimizer’s final output using trace flag 8607: This output shows the (incorrect, but understandable) 365 row estimate for the index range operation, and the correct 104 estimate still attached to its PhyOp_NOP. This tree still has to go through a few post-optimizer rewrites and ‘copy out’ from the memo structure into a tree suitable for the execution engine. One step in this process removes PhyOp_NOP, discarding its 104-row cardinality estimate as it does so. To finish this section on a more positive note, consider what happens if we add an OVER clause to the query aggregate. This isn’t intended to be a ‘fix’ of any sort, I just want to show you that the 104 estimate can survive and be used if later cardinality estimation needs it: SELECT Days = COUNT_BIG(*) OVER () FROM dbo.Calendar AS C WHERE theYear = 2013 AND isWeekday = 0; The estimated execution plan is: Note the 365 estimate at the Index Seek, but the 104 lives again at the Segment! We can imagine the lost predicate ‘isWeekday = 0’ as sitting between the seek and the segment in an invisible Filter operator that drops the estimate from 365 to 104. Even though the NOP group is removed after optimization (so we don’t see it in the execution plan) bear in mind that all cost-based choices were made with the 104-row memo group present, so although things look a bit odd, it shouldn’t affect the optimizer’s plan selection. I should also mention that we can work around the estimation issue by including the index’s filtering columns in the index key: CREATE NONCLUSTERED INDEX Weekends ON dbo.Calendar(theYear, isWeekday) WHERE isWeekday = 0 WITH (DROP_EXISTING = ON); There are some downsides to doing this, including that changes to the isWeekday column may now require Halloween Protection, but that is unlikely to be a big problem for a static calendar table ;)  With the updated index in place, the original query produces an execution plan with the correct cardinality estimation showing at the Index Seek: That’s all for today, remember to let me know about any Switch plans you come across on a modern instance of SQL Server! Finally, here are some other posts of mine that cover other plan operators: Segment and Sequence Project Common Subexpression Spools Why Plan Operators Run Backwards Row Goals and the Top Operator Hash Match Flow Distinct Top N Sort Index Spools and Page Splits Singleton and Range Seeks Bitmaps Hash Join Performance Compute Scalar © 2013 Paul White – All Rights Reserved Twitter: @SQL_Kiwi

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