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  • Are protected constructors considered good practice?

    - by Álvaro G. Vicario
    I'm writing some little helper classes to handle trees. Basically, I have a node and a special root node that represents the tree. I want to keep it generic and simple. This is part of the code: <?php class Tree extends TreeNode{ public function addById($node_id, $parent_id, $generic_content){ if( $parent = $this->findNodeById($parent_id) ){ $parent->addChildById($node_id, $generic_content); } } } class TreeNode{ public function __construct($node_id, $parent_id, $generic_content){ // ... } protected function addChildById($node_id, $generic_content){ $this->children[] = new TreeNode($this->node_id, $node_id, $generic_content); } } $Categories = new Tree; $Categories->addById(1, NULL, $foo); $Categories->addById(2, NULL, $bar); $Categories->addById(3, 1, $gee); ?> My questions: Is it sensible to force TreeNode instances to be created through TreeNode::addById()? If it's so, would it be good practise to declare TreeNode::__construct() as private/protected?

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  • List<string> doesn't update the UI when change occurs [WPF]

    - by Hard Turner
    <ListBox x:Name="MainList" HorizontalAlignment="Left" Height="468" Margin="10,10,0,0" VerticalAlignment="Top" Width="100" ItemsSource="{Binding Items,Mode=TwoWay}" DisplayMemberPath="Name"/> [Serializable()] public class MYcontainer : INotifyPropertyChanged,ISerializable { private List<MYClass> _items = new List<MYClass>(); public List<MYClass> Items { get{ return _items;} set { this._items =value; OnPropertyChanged("Items"); } public event PropertyChangedEventHandler PropertyChanged; public void OnPropertyChanged(string propertyName = null) { var eventHandler = this.PropertyChanged; if (eventHandler != null) eventHandler(this, new PropertyChangedEventArgs(propertyName)); } } when i add an item to "Items" the UI doesnt update, the binding is working fine, since if i closed the window and opened it again, the new items appear correctly what am i doing wrong? i know if i used observablecollection it will work fine, but shouldn't it work with List<? , i already have in another window a string[] property and it update fine

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  • findNode in binary search tree

    - by Weadadada Awda
    Does this look right? I mean I am trying to implement the delete function. Node* BST::findNode(int tofind) { Node* node = new Node; node = root; while (node != NULL) { if (node->val == tofind) { return node; } else if (tofind < node->val) { node = node->left; } else { node = node->right; } } } Here is the delete, it's not even close to done but, void BST::Delete(int todelete) { // bool found = false; Node* toDelete = new Node(); toDelete=findNode(todelete); if(toDelete->val!=NULL) { cout << toDelete->val << endl; } } This causes a segmentation fault just running that, any ideas?

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  • linq and contains

    - by kusanagi
    i have func public PageOfList<ConsaltQuestion> Filter(int? type, int pageId, EntityCollection<ConsaltCost> ConsaltRoles) { // return _dataContext.ConsaltQuestion.Where((o => o.Type == type || type == null) && (o=>o.Paid == paid)); return (from i in _dataContext.ConsaltQuestion where ((i.Type == type || type == null) && (i.Paid == true) && (ConsaltRoles.Contains(ConsaltCostDetails(i.Type.Value)))) select i).ToList().ToPageOfList(pageId, 20); } it return error LINQ to Entities does not recognize the method 'Boolean Contains(mrhome.Models.ConsaltCost)' method, and this method cannot be translated into a store expression. how can i fix it?

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  • How select data from SQLite table where date = week of year?

    - by vovaxo
    I have table expense: "create table " + Expense.TABLE_NAME + "(" + Expense.ID + " integer primary key autoincrement not null, " + Expense.CATEGORY_ID + " integer, " + Expense.ITEM + " text, " + Expense.PRICE + " real, " + Expense.DATE + " date, " + Expense.TIME + " time);"; And I want to select Expense.PRICE where Expense.DATE = current day/week/month. I tried to do this cursor = mDB.rawQuery("select " + Expense.PRICE + " where " + " (strftime('%W', " + Expense.DATE + "))" + "=" + week, null); where week is week = calendar.get(Calendar.WEEK_OF_YEAR); but it gives an error in cursor: 09-15 09:32:02.647: E/AndroidRuntime(18939): Caused by: java.lang.NullPointerException 09-15 09:32:02.647: E/AndroidRuntime(18939): at com.pllug.summercamp.expensemanager.DataAdapter.getPrice(DataAdapter.java:242)

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  • Translating this query in LINQ ? (list of like)

    - by Erick
    I would like to translate this query in LINQ ... it is very easy to construct if we do it in pure SQL but in dynamically created LINQ query (building a search query based on user input) it's a whole new story. SELECT * FROM MyTable WHERE 1=1 AND Column2 IN (1,2,3) AND ( Column1 LIKE '%a%' OR Column1 LIKE '%b%' ) Now to try to construct this we tried it this way : if(myOjb.Column2Collection != null) query = query.where(f => f.Column2.Contains(myOjb.Column2Collection)); if(myObj.Column1Collection != null) { // tough part here ? //query = query.Where(); ... } So what would be the best aproach to this normally ? Note that I am aware of the SqlMethod.Like, tho I can't figure a way to implement it here ...

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  • ASP.Net mysterious behaviour

    - by kalan
    Does anyone have any idea why this works (expression in the if-clause) if (!(childNode.Roles != null && !Helper.HasEqualElements((string[])childNode.Roles, System.Web.Security.Roles.GetRolesForUser()))) AddNode(childNode, parentNode); And this doesn't if (childNode.Roles == null || Helper.HasEqualElements((string[])childNode.Roles, System.Web.Security.Roles.GetRolesForUser())) AddNode(childNode, parentNode); The problem is that the second if-clause sometimes doesn't work. Though it always works in debug mode, but it sometimes fails while running. And the strange thing is that these two pieces of code seems absolutely equal for me.

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  • Two collections and a for loop. (Urgent help needed) Checking an object variable against an inputted

    - by Elliott
    Hi there, I'm relatively new to java, I'm certain the error is trivial. But can't for the life of me spot it. I have an end of term exam on monday and currently trying to get to grips with past papers! Anyway heregoes, in another method (ALGO_1) I search over elements of and check the value H_NAME equals a value entered in the main. When I attempt to run the code I get a null pointer exception, also upon trying to print (with System.out.println etc) the H_NAME value after each for loop in the snippet I also get a null statement returned to me. I am fairly certain that the collection is simply not storing the data gathered up by the Scanner. But then again when I check the collection size with size() it is about the right size. Either way I'm pretty lost and would appreciate the help. Main questions I guess to ask are: from the readBackground method is the data.add in the wrong place? is the snippet simply structured wrongly? oh and another point when I use System.out.println to check the Background object values name, starttime, increment etc they print out fine. Thanks in advance.(PS im guessing the formatting is terrible, apologies.) snippet of code: for(Hydro hd: hydros){ System.out.println(hd.H_NAME); for(Background back : backgs){ System.out.println(back.H_NAME); if(back.H_NAME.equals(hydroName)){ //get error here public static Collection<Background> readBackground(String url) throws IOException { URL u = new URL(url); InputStream is = u.openStream(); InputStreamReader isr = new InputStreamReader(is); BufferedReader b = new BufferedReader(isr); String line =""; Vector<Background> data = new Vector<Background>(); while((line = b.readLine())!= null){ Scanner s = new Scanner(line); String name = s.next(); double starttime = Double.parseDouble(s.next()); double increment = Double.parseDouble(s.next()); double sum = 0; double p = 0; double nterms = 0; while((s.hasNextDouble())){ p = Double.parseDouble(s.next()); nterms++; sum += p; } double pbmean = sum/nterms; Background SAMP = new Background(name, starttime, increment, pbmean); data.add(SAMP); } return data; } Edit/Delete Message

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  • How to open connection to local network path protected by password in smart way? (Whith C#)

    - by lfx
    Hi, I developing program witch have to write some data in file whom are stored in network computer witch are protected by password. Now I'm doing this way - open connection with cmd then write data. static bool ConnectToSrv() { String myUser = "domain.local\\user"; String myPass = "pwd"; String cmdString = "net use \\\\otherPC\\folder\\ /user:" + myUser + " " + myPass; try { ManagementClass processClass = new ManagementClass("Win32_Process"); object[] methodArgs = { cmdString, null, null, 0 }; object result = processClass.InvokeMethod("Create", methodArgs); return true; } catch (System.Exception error) { return false; } } public void writeDate(string data){ } I believe there must by better way. I mean the .NET way. Does anybody know how to do it? :) Thanks

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  • Does NavigationHandler.handleNavigation() clear the flash?

    - by kgrad
    I am using JSF2.0 Mojarra 2.0.2. I have a method that logs out a user and puts a logout message in the flash, forwards to the login page (which has a div that prints out the flash). However, when I use navigationHandlers handleNavigation method for some reason the flash is not being displayed. I have a similar method that forwards a user to the login page if he/she isn't logged in. If I handle the navigation through an h:link and just call the logout method directly, the flash is displayed as normal, but if I use the handleNavigation() method, the flash is cleared for some reason. The code in question is: public void performLogout() { getFacesContext().getExternalContext().invalidateSession(); setCurrentUser(null); getFlash().put("notice", "Successfully logged out."); super.getFacesContext().getApplication().getNavigationHandler() .handleNavigation(getFacesContext(), null, "login"); } Is there some way I can keep the flash when navigating like this? thanks.

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  • how to save state of dynamically created editTexts

    - by user922531
    I'm stuck at how to save the state of my EditTexts on screen orientation. Currently if text is inputted into the EditTexts and the screen is orientated, the fields are wiped (as expected). I am already calling onSaveInstanceState and saving a String, but I have no clue on how to save the EditTexts which are created in code and then retrieve them and add them to the EditTexts when redrawing the activity. Snippet of my code: My main activity is as follows: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); // get the multidim array b = getIntent().getBundleExtra("obj"); m = (Methods) b.getSerializable("Methods"); // method to draw the layout InitialiseUI(); // Restore UI state from the savedInstanceState. if (savedInstanceState != null) { String strValue = savedInstanceState.getString("light"); if (strValue != null) { FLight = strValue; } } try { mCamera = Camera.open(); if (FLight.equals("true")) { flashLight(); } } catch (Exception e) { Log.d(TAG, "Thrown exception onCreate() camera: " + e); } } // end onCreate /** Called when the back button is pressed. */ @Override public void onResume() { super.onResume(); try { mCamera = Camera.open(); if (FLight.equals("true")) { flashLight(); } } catch (Exception e) { Log.d(TAG, "Thrown exception onCreate() camera: " + e); } } // end onCreate /** saves data before leaving the screen */ @Override protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putString("light", FLight); } /** called when exiting / leaving the screen */ @Override protected void onPause() { super.onPause(); Log.d(TAG, "onPause()"); if (mCamera != null) { mCamera.stopPreview(); mCamera.release(); mCamera = null; } } /* * set up the UI elements - add click listeners to buttons used in * onCreate() and onConfigurationChanged() * * Set the editTexts fields to show the previous readings as Hints */ public void InitialiseUI() { Log.d(TAG, "Start of InitialiseUI, Main activity"); // get a reference to the TableLayout final TableLayout myTLreads = (TableLayout) findViewById(R.id.myTLreads); // Create arrays to hold the TVs and ETs final TextView[] myTextViews = new TextView[m.getNoRows()]; // create an empty array; final EditText[] myEditTexts = new EditText[m.getNoRows()]; // create an empty array; for(int i =0; i<=m.getNoRows()-1;i++ ){ TableRow tr=new TableRow(this); tr.setLayoutParams(new LayoutParams( LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT)); // create a new textview / editText final TextView rowTextView = new TextView(this); final EditText rowEditText = new EditText(this); // setWidth is needed otherwise my landscape layout is OFF rowEditText.setWidth(400); // this stops the keyboard taking up the whole screen in landscape layout rowEditText.setImeOptions(EditorInfo.IME_FLAG_NO_EXTRACT_UI); // add some padding to the right of the TV rowTextView.setPadding(0,0,10,0); // set colors to white rowTextView.setTextColor(Color.parseColor("#FFFFFF")); rowEditText.setTextColor(Color.parseColor("#FFFFFF")); // if readings already sent today set color to yellow if(m.getTransmit(i+1)==false){ rowEditText.setEnabled(false); rowEditText.setHintTextColor(Color.parseColor("#FFFF00")); } // set the text of the TV to the meter name rowTextView.setText(m.getMeterName(i+1)); // set the hint of the ET to the last submitted reading rowEditText.setHint(m.getLastReadString(i+1)); // add the textview to the linearlayout rowEditText.setInputType(InputType.TYPE_CLASS_PHONE);//InputType.TYPE_NUMBER_FLAG_DECIMAL); tr.addView(rowTextView); tr.addView(rowEditText); myTLreads.addView(tr); // add a reference to the textView myTextViews[i] = rowTextView; myEditTexts[i] = rowEditText; } final Button submit = (Button) findViewById(R.id.submitReadings); // add a click listener to the button try { submit.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { Log.d(TAG, "Submit button clicked, Main activity"); preSubmitCheck(m.getAccNo(), m.getPostCode(), myEditTexts); // method to do HTML getting and sending } }); } catch (Exception e) { Log.d(TAG, "Exceptions (submit button)" + e.toString()); } }// end of InitialiseUI I don't need to do anything with these values until a button is clicked. Would it be easier if they were a ListView, i'm guessing I would still have the problem of saving them and retrieving them on rotation. If it helps I have an object m which is a string[][] I could temporarily somehow store them in

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  • Why are awkward numbers and letters in my query string??

    - by Nicole
    Hi everyone!! I have a MVC website and when I execute it, the query string (url) that appears is: http://localhost:6970/(S(51aegi45qneolxa0oxwuzh55))/default.aspx what the hell is that strange combination of numbers and letters??? please help!!!!! previously i had been working with the session expires to redirect to one of my views, could be something of that?? i have added the following action filter: public override void OnActionExecuting(ActionExecutingContext filterContext) { HttpContextBase ctx = filterContext.HttpContext; // check if session is supported if (ctx.Session != null) { // check if a new session id was generated if (ctx.Session.IsNewSession) { // If it says it is a new session, but an existing cookie exists, then it must // have timed out string sessionCookie = ctx.Request.Headers["Cookie"]; if ((null != sessionCookie) && (sessionCookie.IndexOf("ASP.NET_SessionId") >= 0)) { filterContext.HttpContext.Response.Redirect("~/Error/SesionExpirada", true); } } } base.OnActionExecuting(filterContext); } but if I put it in ignore it stills add that rare thing to my urls. Please help!!! thanks

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  • Bug in Programming Interviews Exposed?

    - by Sam
    Hi, I could not find an errata for the 2nd edition of this book. My question concerns the if-statement in the following piece of code. void removeHead (Node ** head) { Node * temp; if (!(*head)) { temp = (*head)->next; delete *head; *head = temp; } } So I understand that the point of the if-statement is to check if the Node is null. However by adding an additional "!" to the evaluation, wouldn't this negate the false value of null? Would it be correct to change it to something like: if (*head) { ... } Also if anyone knows where I can find an official errata for the 2nd edition that would be great. Thanks, Sam

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  • How much memory is reserved when i declare a string?

    - by Bhagya
    What exactly happens, in terms of memory, when i declare something like: char arr[4]; How many bytes are reserved for arr? How is null string accommodated when I 'strcpy' a string of length 4 in arr? I was writing a socket program, and when I tried to suffix NULL at arr[4] (i.e. the 5th memory location), I ended up replacing the values of some other variables of the program (overflow) and got into a big time mess. Any descriptions of how compilers (gcc is what I used) manage memory?

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  • Java - Layering issues with Lists and Graphics2D

    - by Mirrorcrazy
    So I have a DisplayPanel class that extends JPanel and that also paints my numerous images for my program using Graphics2D. In order to be able to easily customly use this I set it up so that every time the panel is repainted it uses a List, that I can add to or remove from as the program processes. My problem is with layering. I've run into an issue where the List must have reached its resizing point (or something whacky like that) and so the images i want to display end up beneath all of the other images already on the screen. I've come to the community for an answer because I have faith you will provide a good one. DisplayPanel: package earthworm; import java.awt.Graphics; import java.awt.Graphics2D; import java.util.ArrayList; import java.util.List; import javax.swing.JPanel; public class DisplayPanel extends JPanel { private List<ImageMap> images = new ArrayList(); public DisplayPanel() { setSize(800, 640); refresh(); } public void refresh() { revalidate(); repaint(); } @Override public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g; g2d.clearRect(0, 0, 800, 640); for(int i = 0; i < images.size(); i++) g2d.drawImage( images.get(i).getImage(), images.get(i).getX(), images.get(i).getY(), null); } public void paintImage(ImageMap[] images, ImageMap[] clearImages, boolean clear) { if(clear) this.images.clear(); else if(clearImages!=null) for(int i = 0; i < clearImages.length; i++) this.images.remove(clearImages[i]); if(images!=null) for(int i = 0; i<images.length; i++) this.images.add(images[i]); refresh(); } }

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  • How do I avoid boxing/unboxing when extending System.Object?

    - by Robert H.
    I'm working on an extension method that's only applicable to reference types. I think, however, it's currently boxing and unboxing the the value. How can I avoid this? namespace System { public static class SystemExtensions { public static TResult GetOrDefaultIfNull<T, TResult>(this T obj, Func<T, TResult> getValue, TResult defaultValue) { if (obj == null) return defaultValue; return getValue(obj); } } } Example usage: public class Foo { public int Bar { get; set; } } In some method: Foo aFooObject = new Foo { Bar = 1 }; Foo nullReference = null; Console.WriteLine(aFooObject.GetOrDefaultIfNull((o) => o.Bar, 0)); // results: 1 Console.WriteLine(nullReference.GetOrDefaultIfNull((o) => o.Bar, 0)); // results: 0

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  • Bad allocation exceptions in C++

    - by me1982
    Hello, In a school project of mine I was requested to create a program not using STL. In the program I use alot of Pointer* = new Something; if (Pointer == NULL) throw AllocationError(); My question is about allocation errors: 1. is there an autamtic exception thrown by new when allocation fails? 2. if so how can I catch it if I'm not using STL (#include "exception.h) 3. is using the NULL testing enugh? thank you. I'm using eclipseCDT(C++) with MinGW on windows 7.

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  • Linked List Inserting in sorted format

    - by user2738718
    package practise; public class Node { public int data; public Node next; public Node (int data, Node next) { this.data = data; this.next = next; } public int size (Node list) { int count = 0; while(list != null){ list = list.next; count++; } return count; } public static Node insert(Node head, int value) { Node T; if (head == null || head.data <= value) { T = new Node(value,head); return T; } else { head.next = insert(head.next, value); return head; } } } This work fine for all data values less than the first or the head. anything greater than than doesn't get added to the list.please explain in simple terms thanks.

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  • Why is TargetInvocationException treated as uncaught by the IDE?

    - by Jason Coyne
    I have some code that is using reflection to pull property values from an object. In some cases the properties may throw exceptions, because they have null references etc. try { child.Target = propertyInfo.GetValue(target, null); } catch (TargetInvocationException ex) { child.Target = ex.InnerException.Message; } catch (Exception ex) { child.Target = ex.Message; } Ultimately the code works correctly, however when I am running under the debugger : When the property throws an exception, the IDE drops into the debugger as if the exception was uncaught. If I just hit run, the program flows through and the exception comes out as a TargetInvocationException with the real exception in the InnerException property. How can I stop this from happening?

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  • mysql add auto increment and a additional key

    - by Lee
    Hey all I am trying to alter a table with adding a new column setting it as auto increment and with a key. The table already has one key and this one will be an addition. The error I get is the following. error : Multiple primary key defined My code is: alter table user add column id int (11) NOT NULL AUTO_INCREMENT PRIMARY KEY FIRST; I have also tries wrapping the key name ie alter table user add column id int (11) NOT NULL AUTO_INCREMENT PRIMARY (id) KEY FIRST; But still no luck. How can it be done ?

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  • SQL Server 2000 - Filter by String Length

    - by user208662
    Hello, I have a database on a SQL Server 2000 server. This database has a table called "Person" that has a field call "FullName" that is a VARCHAR(100). I am trying to write a query that will allow me to get all records that have a name. Records that do not have a name have a FullName value of either null or an empty string. How do I get all of the Person records have a FullName? In other words, I want to ignore the records that do not have a FullName. Currently I am trying the following: SELECT * FROM Person p WHERE p.FullName IS NOT NULL AND LEN(p.FullName) > 0 Thank you

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  • Why MySQL multiple-column index is overpopulated?

    - by actual
    Consider following MySQL table: CREATE TABLE `log` ( `what` enum('add', 'edit', 'remove') CHARACTER SET ascii COLLATE ascii_bin NOT NULL, `with` int(10) unsigned NOT NULL, KEY `with_what` (`with`,`what`) ) ENGINE=InnoDB; INSERT INTO `log` (`what`, `with`) VALUES ('add', 1), ('edit', 1), ('add', 2), ('remove', 2); As I understand, with_what index must have 2 unique entries on its first with level and 3 unique entries in what "subindex". But MySQL reports 4 unique entries for each level. In other words, number of unique elements for each level is always equal to number of rows in log table. Is that a bug, a feature or my misunderstanding?

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  • Getting ready for learn html5

    - by vtortola
    Hi, I'm a desktop application developer, and I plan learning html5, but as it's not released, there is no (almost) published books and no too much infomation from beginners on the web... I fell I should start with html4 and the current web development skills. I think, I should start with html4, css and javascript... but there are so many technologies related that I get lost :D So, what current technologies will be sill used when html5 be released? I mean, what about "jquery" and "ajax"? I know they are javascript under the hood, but will they still make sense in the future? What would you recommend me considering that I have just a little bit of html knowlegde, almost null CSS and completely null in javascript? Thanks in advance.

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  • how to get count column

    - by soclose
    Hi I'd like to get the value of Count column from cursor. public Cursor getRCount(String iplace) throws SQLException { try { String strSql = "SELECT COUNT(_id) AS RCount FROM tbName WHERE place= '" + iplace + "'"; return db.rawQuery(strSql, null); } catch (SQLException e) { Log.e("Exception on query", e.toString()); return null; } } I tried to get this count column value from cursor like below Cursor cR = mDbHelper.getRCount(cplace);if (cR.getCount() > 0){long lCount = cR.getLong(0);}cR.close();} I got the debug error. How to get it?

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  • Problem with non data bound value in ASP.NET DropDownList.

    - by ProfK
    I'm trying to 'inject' an [All Regions] item into my regions dropdown, as follows: <asp:DropDownList ID="regionList" runat="server" AutoPostBack="true" AppendDataBoundItems="true" Width="200px" DataSourceID="regionDataSource" DataTextField="Desc" DataValueField="RegionId"> <asp:ListItem Selected="True" Value="">[All Regions]</asp:ListItem> </asp:DropDownList> I also have a rank dropdown, for taxi ranks in a region, with the following select parameter: <asp:ControlParameter ControlID="regionList" Name="RegionId" PropertyName="SelectedValue" Type="Int32" DefaultValue="" ConvertEmptyStringToNull="true" /> So the expected behaviour is that when [All Regions] is selected, the ranks dropdown should get a null parameter, and mt SQL selects all ranks, for all regions. I know my SQL works with a null parameter, but the ranks dropdown is not data binding when I select [All Regions] on the region list. It binds when I select a region from the DB, but keeps that binding when I select [All Regions] again. What am I doing wrong?

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