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  • Why can't I enforce derived classes to have parameterless constructors?

    - by FrisbeeBen
    I am trying to do the following: public class foo<T> where T : bar, new() { public foo() { _t = new T(); } private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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  • How does the below program work in c++?

    - by Srinivasa Varadan
    I have just created 2 pointers which has undefined behavior and try to invoke a class member function which has no object created ? I don't understand this? #include<iostream> using namespace std; class Animal { public: void talk() { cout<<"I am an animal"<<endl; } }; class Dog : public Animal { public: void talk() { cout<<"bark"<<endl; } }; int main() { Animal * a; Dog * d; d->talk(); a->talk(); }

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  • toupper/tolower + locale (german)

    - by Oops
    Hi, how to convert a string (wstring) from lowercase to uppercase characters and vice versa? I searched the net and found there is a STL-function std::transform. But until now I hav'nt figured out how to give the right locale-object for example "Germany_german" to the function. Who can help please? my code looks like: wstring strin = L"ABCÄÖÜabcäöü"; wstring str = strin; locale loc( "Germany_german" ); // ??? how to apply this ??? std::transform( str.begin(), str.end(), str.begin(), (int(*)(int)tolower ); //result: "abcäöüabcäöü" The characters ÄÖÜ and äöü (it's like Ae, Oe, Ue) will not be converted correctly. P.S.: I don't prefer a big switch sweat and also I know BOOST is capable of everything, i would prefer a STL solution. thanks in advance Oops

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  • How do I use a graphics method to pass parameters? Example is below.

    - by sonny5
    private static void getCorners(out float Wx, out float Wy, out float Vx, out float Vy) { // note-- I don't know how to flip the Y axis using this method... this is not a "graphics" method // In other words, I should use something like: // flipY(object sender, System.EventArgs e); // but don't know the syntax or whatever // I tried to do this: //Graphics g = this.CreateGraphic //Matrix myMatrix2 = new Matrix(1, 0, 0, -1, 0, 0); // flip Y axis //g.Transform = myMatrix2; //g.TranslateTransform(0, 480, MatrixOrder.Append); // ...but I get the error: // error CS0026: Keyword 'this' is not valid in a static property, static method, or // static field initializer Wx = 1.00F; Wy = 1.00F; // make this 1.00 (not 3.00F) down from the TOP since cannot get Y flipped Vx = ((Wx- WXmin)*((VXmax-VXmin)+VXmin)/(WXmax-WXmin)); Vy = ((Wy-WYmin)*(VYmax-VYmin)/(WYmax-WYmin)+VYmin); } thanks, Sonny5

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  • Best way of invoking getter by reflection

    - by Javi
    Hello, I need to get the value of a field with a specific annotation, So with reflection I am able to get this Field Object. The problem is that this field will be always private though I know in advance it will always have a getter method. I know that I can use setAccesible(true) and get its value (when there is no PermissionManager), though I prefer to invoke its getter method. I know that I could look for the method by looking for "get+fieldName" (though I know for example for boolean fields are sometimes named as "is+fieldName"). I wonder if there is a better way to invoke this getter (many frameworks use getters/setters to access the attributes so maybe they do in another way). Thanks

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  • Infinite loop when Selecting a panel?

    - by serhio
    I have a winform in witch I have a custom LongPanel with textboxes. In order to validate an eventually edited textbox when the user click somewhere out of textBoxY I use the following code: Private Sub LongPanel_MouseClick(ByVal sender As Object, _ ByVal e As MouseEventArgs) _ Handles MyBase.MouseClick _AttachedPanel.Select() End Sub In runtime application freezes at the "Select" line... I receive infinite panel Leave events(sender is a panel)... any idea why? EDIT: precision on panels parents: Form => SplitPanel => _AttachedPanel | _LongPanel (_LongPanel contains a reference to _AttachedPanel)

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  • Best way to make an attribute always an array?

    - by Shadowfirebird
    I'm using my MOO project to teach myself Test Driven Design, and it's taking me interesting places. For example, I wrote a test that said an attribute on a particular object should always return an array, so -- t = Thing.new("test") p t.names #-> ["test"] t.names = nil p t.names #-> [] The code I have for this is okay, but it doesn't seem terribly ruby to me: class Thing def initialize(names) self.names = names end def names=(n) n = [] if n.nil? n = [n] unless n.instance_of?(Array) @names = n end attr_reader :names end Is there a more elegant, Ruby-ish way of doing this? (NB: if anyone wants to tell me why this is a dumb test to write, that would be interesting too...)

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  • selected index event is not working in dropdown

    - by prince23
    <asp:DropDownList ID="ddlTime" runat="server" CausesValidation="true" AutoPostBack="true" onselectedindexchanged="ddlTime_SelectedIndexChanged"> <asp:ListItem Selected Value = "True">--Select--</asp:ListItem> <asp:ListItem>8.50</asp:ListItem> <asp:ListItem>9.00</asp:ListItem> <asp:ListItem>9.50</asp:ListItem> </asp:DropDownList> I have drop down with the event changing . but when ever i select an value this event is not firing at all protected void ddlTime_SelectedIndexChanged(object sender, EventArgs e) { } What is the issue that is causing here any help would be great thank you

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  • How can I assign a DBNull in a better way?

    - by Mike
    Hi, I need to parse value from a datarow and assign it to another datarow.If the input is valid, then I need to parse it to double or else add a dbnull value to the output.I'm doing the following, is there a better way to do it? public double? GetVolume(object data) { string colValue = data == null ? string.Empty : data.ToString(); double volume; if (!Double.TryParse(colValue.ToString(), out volume)) { return null; } return volume; } public void Assign(DataRow theRowInput,DataRow theRowOutput) { double? volume = GetVolume(theRowInput[0]); if(volumne.HasValue) theRowOutput[0] = volume.value; else theRowOutput[0] = DbNull.Value; return theRowOutput; } Thanks, -M

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  • Is there any way to use imagegrabwindow() with Firefox or Chrome?

    - by patternsofchaos
    I'm trying to generate website thumbnails programatically in PHP. To do this, I'm using imagegrabwindow() with a COM object: $browser = new COM("InternetExplorer.Application"); $handle = $browser->HWND; $browser->Visible = true; $browser->Navigate($pre.$URL); while ($browser->Busy) { com_message_pump(4000); } $img = imagegrabwindow($handle); What I'm wondering is if there is any way to do the same thing with Firefox or Chrome? Can I invoke either of them with PHP COM?

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  • KeyDown event is not Working for Arrow keys ,Home , End ,Pageup,Pagedown and other similar keys in s

    - by Subhen
    Hi , I want to over ride the selection behaviour of listbox Items. We can traverse through listbox items using Up and Down arrows where as I wan to traverse the list using Left and Right arrow keys. While I am trying to add the key down event for Listbox, It shows almost all key presses except for Arrow Keys, Home, End and Similar keys. I have the following Code: private void listArtist_KeyDown(object sender, System.Windows.Input.KeyEventArgs e) { if (e.Key.ToString() == "Enter") { //Go to Some Page } else { MessageBox.Show(e.Key.ToString()); } } I am clue less about it. Please help. Thanks, Subhen

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  • Is it possible in Scala to force the caller to specify a type parameter for a polymorphic method ?

    - by Alex Kravets
    //API class Node class Person extends Node object Finder { def find[T <: Node](name: String): T = doFind(name).asInstanceOf[T] } //Call site (correct) val person = find[Person]("joe") //Call site (dies with a ClassCast inside b/c inferred type is Nothing) val person = find("joe") In the code above the client site "forgot" to specify the type parameter, as the API writer I want that to mean "just return Node". Is there any way to define a generic method (not a class) to achieve this (or equivalent). Note: using a manifest inside the implementation to do the cast if (manifest != scala.reflect.Manifest.Nothing) won't compile ... I have a nagging feeling that some Scala Wizard knows how to use Predef.<:< for this :-) Ideas ?

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  • Imbedded wpf textbox does not accept input

    - by pro3carp3
    I put a wpf textbox inside a combobox to allow the user to enter a custom setting. I can read the keypress in the keydown event, but the text in the textbox does not change. What am I missing? <ComboBoxItem Name="GridSizeCustom"> <StackPanel Height="30" Orientation="Horizontal"> <TextBlock Text="Grid Size (8 - 200)" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="0" /> <TextBox Name="GridSizeBox" KeyDown="test" Width="50" /> </StackPanel> </ComboBoxItem> I step through this event handler when I press a key, but no change to the textbox text: public void test(Object sender, KeyboardEventArgs e) { int x = 0; } Any help is appreciated. Thanks.

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  • Selecting a sequence of elements from the IList

    - by KhanS
    I have a IList. where the object PersonDetails consists of the persons name, address and phone number. The list consists of more than 1000 person details. I would like to display 50 PersonDetails per page. Is there a way to select only 50 elements from the list, and return them. For example. myList.select(1,50) myList.select(51, 100) I am able to select only first 50 by using. myList.Take(50); The entire list is at the wcf service, and i would like to get only fifty elements at a time.

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  • how do you set a property of a control to an address of a function in xaml?

    - by ambog36
    Hi, I have a control that has a "Filter" property that expects a function that defines how the contents of the control should be filtered. so far i am setting the filter in code behind as such: MyControl.Filter = AddressOf Filters.MyFilter In this example MyFilter is a shared function in the Filters class with the following signature: Public Shared Function MyFilter(ByVal obj As Object, ByVal text As String) As Boolean I would like to set this in xaml. I was thinking of setting the Filters.MyFilter as a static resource and setting it that way: ...Filter="{StaticResource myFilter}"/ but i cant set Filters.MyFilter as a static resource. Any ideas on how to achieve this? Thanks,

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  • Method for SharePoint list/item locking across processes/machines?

    - by Steve
    In general, is there a decent way in SharePoint to control race conditions due to two processes or even two machines in the farm operating on the same list or list item at the same time? That is, is there any mechanism either built in or that can be fabricated via the Object Model for doing cross-process or cross-machine locking of individual list items? I want to write a timer job that performs a bunch of manipulations on a list. This list is written to by the SharePoint UI and then read by the UI. I want to be able to make sure that the UI doesn't either write to or read from the list when it is in an inconsistent state due to the timer job being in the middle of a manipulation. Is there any way to do this? Also, I want to allow for multiple instances of the timer job to run simultaneously. This, again, will require a lock to be sure that the two jobs don't attempt to operate on the same list/item at the same time. TIA for any help!

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  • Why doesn't the C++ default destructor destroy my objects?

    - by Oszkar
    The C++ specification says the default destructor deletes all non-static members. Nevertheless, I can't manage to achieve that. I have this: class N { public: ~N() { std::cout << "Destroying object of type N"; } }; class M { public: M() { n = new N; } // ~M() { //this should happen by default // delete n; // } private: N* n; }; Then this should print the given message, but it doesn't: M* m = new M(); delete m; //this should invoke the default destructor

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  • Dictionary as parameter, where the Value-Type is irrelevant

    - by aaginor
    Hi folks, I have a function, that returns the next higher value of a Dictionary-Keys-List compared to a given value. If we have a Key-List of {1, 4, 10, 24} and a given value of 8, the function would return 10. Obviously the type of the Value-Part of the Dictionary doesn't matter for the function, the function-code for a Dictionary<int, int> and Dictionary<int, myClass> would be the same. How has the method-head have to look like, when I want to call the function with any Dictionary, that has int as key-Type and the value-Type is irrelevant? I tried: private int GetClosedKey(Dictionary<int, object> list, int theValue); but it says that there are illegal arguments, when I call it with a Dictionary. I don't want to copy'n'paste the function for each different value-type that my function may be called. Any idea, how to accomplish that? Thanks in advance, Frank

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  • Movement in game programming

    - by hanesjw
    This question may have been asked before, but I'm starting to get into game programming on the Android. I'm having a hard time figuring out the best way to move an object. To put it simply, lets say I have a bitmap located on 0,0 and i want to move it across the screen. The obvious way to do it would be to simply increment the X position by one every time the Surface View onDraw method gets called. But what if I wanted to make it move faster? I could increment it by two or three instead of one, but then the movement starts to get really choppy and stupid looking. What is the best way to go about doing this?

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  • C#: Select row from DataGridView

    - by Bi
    Hi I have a form with a DataGridView (of 3 columns) and a Button. Every time the user clicks on a button, I want the get the values stored in the 1st column of that row. Here is the code I have: private void myButton_Click(object sender, EventArgs e) { foreach (DataGridViewRow row in ProductsGrid.Rows) { if (this.ProductsGrid.SelectedRows.Count == 1) { // get information of 1st column from the row string value = this.ProductsGrid.SelectedRows[0].Cells[0].ToString(); } } } However when I click on myButton, the this.ProductsGrid.SelectedRows.Count is 0. Also, how do I ensure that the user selects only one row and not multiple rows? Does this code look right?

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  • Detect NativeDragDrop to Trash or RecycleBin

    - by colder
    I will let user remove item from List with a cool method. Drag an item in adobe air List control and then drop it to Trash(OSX) or Recycle Bin(Win). The trash accept move drag action only. So I think I must set dragMoveEnable=true. When I drag an item to Recycle Bin on Windows. It show accept effect(alpha mask) and Air remove that object from List's dataProvider. So I can find which one is disappear. But when I drag to Trash on MacOSX. It show effect too. But Air do nothing for List. Maybe this is a bug. How can I avoid it? Are there any way to detect where dropped by user?

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  • Passing an array of structures to an Oracle stored procedure (CFMX)

    - by Patti
    I'm looking to write a Oracle stored procedure where I would pass in (from ColdFusion) an array of structures and loop over each iteration to insert the bits and pieces within the structures to the DB., I haven't written this type of procedure / package before. I am planning to do an sp / package similar to what is sketched out in the second reply to this thread: How to pass a array of object to oracle stored procedure Assuming I do, how can I call the procedure from ColdFusion (I'm using MX) and pass in my array? As far as I can see, none of the CF_SQL_Types make sense.

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  • It says command.ExecuteNonQuery() is not initialized

    - by Alfrezo
    My code: // Get Connection String string conn = WebConfigurationManager.ConnectionStrings["GraduatesConnectionString"].ToString(); // Create connection object SqlConnection connection = new SqlConnection(conn); SqlCommand command = connection.CreateCommand(); try { // Open the connection. connection.Open(); // Execute the insert command. command.CommandText = ("INSERT INTO PersonalInfo(Id,Name,LastName,ContactNumber, Address,Gender, Date_Of_Birth) VALUES(\'" + (this.txtID.Text + ("\',\'" + (this.txtName.Text + ("\',\'" + (this.txtLastName.Text + ("\',\'" + (this.txtContactNumber.Text + ("\',\'" + (this.txtAddress.Text + ("\',\'" + (this.gender + ("\',\'" + (this.txtDateofBirth.Text + ("\',\'" ))))); command.ExecuteNonQuery(); } finally { // Close the connection. connection.Close(); }

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  • Struggling with how to compare hours with different time zones in Java?

    - by Riki
    Hi! I have 2 date object in the database that represent the company's working hours. I only need the hours but since I have to save date. it appears like this: Date companyWorkStartHour; Date companyWorkEndHour; start hours: 12-12-2001-13:00:00 finish hours: 12-12-2001-18:00:00 I have the timezone of the company and of the user. (my server may be in another timezone). TimeZone userTimeZone; TimeZone companyTimeZone; I need to check if the user's current time (considering his timezone) is within the company working hours (considering the company's time zone). How can I do it? I am struggling for over a week with Java calendar and with no success!

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  • Does SetThreadPriority cause thread reschedulling?

    - by Suma
    Consider following situation, assuming single CPU system: thread A is running with a priority THREAD_PRIORITY_NORMAL, signals event E thread B with a priority THREAD_PRIORITY_LOWEST is waiting for an event E (Note: at this point the thread is not scheduled because it is runnable, but A is higher priority and runnable as well) thread A calls SetThreadPriority(B, THREAD_PRIORITY_ABOVE_NORMAL) Is thread B re-scheduled immediately to run, or is thread A allowed to continue until current time-slice is over, and B is scheduled only once a new time-slice has begun? I would be interested to know the answer for WinXP, Vista and Win7, if possible. Note: the scenario above is simplified from my real world code, where multiple threads are running on multiple cores, but the main object of the question stays: does SetThreadPriority cause thread scheduling to happen?

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