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  • How do I create a check constraint?

    - by Zack Peterson
    Please imagine this small database... Diagram Tables Volunteer Event Shift EventVolunteer ========= ===== ===== ============== Id Id Id EventId Name Name EventId VolunteerId Email Location VolunteerId Phone Day Description Comment Description Start End Associations Volunteers may sign up for multiple events. Events may be staffed by multiple volunteers. An event may have multiple shifts. A shift belongs to only a single event. A shift may be staffed by only a single volunteer. A volunteer may staff multiple shifts. Check Constraints Can I create a check constraint to enforce that no shift is staffed by a volunteer that's not signed up for that shift's event? Can I create a check constraint to enforce that two overlapping shifts are never staffed by the same volunteer?

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  • JQuery getJSON Callback Returning Null Data

    - by user338828
    I have a getJSON call that is called back correctly, but the data variable is null. The python code posted below is executed by the getJSON call to the demandURL. Any ideas? javascript: var demandURL = "/demand/washington/"; $.getJSON(demandURL, function(data) { console.log(data); }); python: data = {"demand_count":"one"} json = simplejson.dumps(data) return HttpResponse(json, mimetype="application/json")

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  • null value exception thrown when deserializing null value JSON.net

    - by Bharath
    Hi Friends I am trying to deserialize a hidden control field into a json object the code is as follows Dim settings As New Newtonsoft.Json.JsonSerializerSettings() settings.NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore Return Newtonsoft.Json.JsonConvert.DeserializeObject(Of testContract)(txtHidden.Text, settings) But I am getting the following exception. value cannot be null parameter name s: I even added the following lines but it still does not work out. Please help settings.MissingMemberHandling = Newtonsoft.Json.MissingMemberHandling.Ignore settings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore settings.ObjectCreationHandling = Newtonsoft.Json.ObjectCreationHandling.Replace Thanks Bharath

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  • What do you think about ??= operator in C#?

    - by TN
    Do you think that C# will support something like ??= operator? Instead of this: if (list == null) list = new List<int>(); It might be possible to write: list ??= new List<int>(); Now, I could use (but it seems to me not well readable): list = list ?? new List<int>();

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  • GetHashCode on null fields?

    - by Shimmy
    How do I deal with null fields in GetHashCode function? Module Module1 Sub Main() Dim c As New Contact Dim hash = c.GetHashCode End Sub Public Class Contact : Implements IEquatable(Of Contact) Public Name As String Public Address As String Public Overloads Function Equals(ByVal other As Contact) As Boolean _ Implements System.IEquatable(Of Contact).Equals Return Name = other.Name AndAlso Address = other.Address End Function Public Overrides Function Equals(ByVal obj As Object) As Boolean If ReferenceEquals(Me, obj) Then Return True If TypeOf obj Is Contact Then Return Equals(DirectCast(obj, Contact)) Else Return False End If End Function Public Overrides Function GetHashCode() As Integer Return Name.GetHashCode Xor Address.GetHashCode End Function End Class End Module

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  • DPAPI encryted section returns null

    - by Jay
    Hi, I am encrypting the appSettings and the connectionStrings sections in the app.config file. But when I try to read the value, its always returning null. I am not sure if I am missing something. I thought the decryption was transparent. Has anyone else had any success with reading DPAPI protected sections in the app.config file.

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  • linq null refactoring code

    - by user276640
    i have code public List<Files> List(int? menuId) { if (menuId == null) { return _dataContext.Files.ToList(); } else { return _dataContext.Files.Where(f => f.Menu.MenuId == menuId).ToList(); } } is it possible to make it only one line like return _dataContext.Files.Where(f = f.Menu.MenuId == menuId).ToList();?

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  • SmartGWT throws JavaScriptException: (null): null

    - by elviejo
    When using GWT 2.0.x and SmartGWT 2.2 Code as simple as: public class SmartGwtTest implements EntryPoint { public void onModuleLoad() { IButton button = new IButton("say hello"); } } will generate the exception. com.google.gwt.core.client.JavaScriptException: (null): This only happens in hosted (devmode) ant hosted I also suspect that maybe the GWT Development Plugin might have something to do with it. Have you found a similar problem? How did you solve it?

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  • Eclipse getResourceAsStream returning null

    - by Chris
    I cannot get getResourceAsStream to find a file. I have put the file in the top level dir, target dir, etc, etc and have tried it with a "/" in front as well. Everytime it returns null. Any suggestions ? Thanks. public class T { public static final void main(String[] args) { InputStream propertiesIS = T.class.getClassLoader().getResourceAsStream("test.txt"); System.out.println("Break"); } }

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  • getting Null pointer exception

    - by Abhijeet
    Hi I am getting this message on emulator when I run my android project: The application MediaPlayerDemo_Video.java (process com.android.MediaPlayerDemo_Video) has stopped unexpectedly. Please try again I am trying to run the MediaPlayerDemo_Video.java given in ApiDemos in the Samples given on developer.android.com. The code is : package com.android.MediaPlayerDemo_Video; import android.app.Activity; import android.media.AudioManager; import android.media.MediaPlayer; import android.media.MediaPlayer.OnBufferingUpdateListener; import android.media.MediaPlayer.OnCompletionListener; import android.media.MediaPlayer.OnPreparedListener; import android.media.MediaPlayer.OnVideoSizeChangedListener; import android.os.Bundle; import android.util.Log; import android.view.SurfaceHolder; import android.view.SurfaceView; import android.widget.Toast; public class MediaPlayerDemo_Video extends Activity implements OnBufferingUpdateListener, OnCompletionListener, OnPreparedListener, OnVideoSizeChangedListener, SurfaceHolder.Callback { private static final String TAG = "MediaPlayerDemo"; private int mVideoWidth; private int mVideoHeight; private MediaPlayer mMediaPlayer; private SurfaceView mPreview; private SurfaceHolder holder; private String path; private Bundle extras; private static final String MEDIA = "media"; // private static final int LOCAL_AUDIO = 1; // private static final int STREAM_AUDIO = 2; // private static final int RESOURCES_AUDIO = 3; private static final int LOCAL_VIDEO = 4; private static final int STREAM_VIDEO = 5; private boolean mIsVideoSizeKnown = false; private boolean mIsVideoReadyToBePlayed = false; /** * * Called when the activity is first created. */ @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.mediaplayer_2); mPreview = (SurfaceView) findViewById(R.id.surface); holder = mPreview.getHolder(); holder.addCallback(this); holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); extras = getIntent().getExtras(); } private void playVideo(Integer Media) { doCleanUp(); try { switch (Media) { case LOCAL_VIDEO: // Set the path variable to a local media file path. path = ""; if (path == "") { // Tell the user to provide a media file URL. Toast .makeText( MediaPlayerDemo_Video.this, "Please edit MediaPlayerDemo_Video Activity, " + "and set the path variable to your media file path." + " Your media file must be stored on sdcard.", Toast.LENGTH_LONG).show(); } break; case STREAM_VIDEO: /* * Set path variable to progressive streamable mp4 or * 3gpp format URL. Http protocol should be used. * Mediaplayer can only play "progressive streamable * contents" which basically means: 1. the movie atom has to * precede all the media data atoms. 2. The clip has to be * reasonably interleaved. * */ path = ""; if (path == "") { // Tell the user to provide a media file URL. Toast .makeText( MediaPlayerDemo_Video.this, "Please edit MediaPlayerDemo_Video Activity," + " and set the path variable to your media file URL.", Toast.LENGTH_LONG).show(); } break; } // Create a new media player and set the listeners mMediaPlayer = new MediaPlayer(); mMediaPlayer.setDataSource(path); mMediaPlayer.setDisplay(holder); mMediaPlayer.prepare(); mMediaPlayer.setOnBufferingUpdateListener(this); mMediaPlayer.setOnCompletionListener(this); mMediaPlayer.setOnPreparedListener(this); mMediaPlayer.setOnVideoSizeChangedListener(this); mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC); } catch (Exception e) { Log.e(TAG, "error: " + e.getMessage(), e); } } public void onBufferingUpdate(MediaPlayer arg0, int percent) { Log.d(TAG, "onBufferingUpdate percent:" + percent); } public void onCompletion(MediaPlayer arg0) { Log.d(TAG, "onCompletion called"); } public void onVideoSizeChanged(MediaPlayer mp, int width, int height) { Log.v(TAG, "onVideoSizeChanged called"); if (width == 0 || height == 0) { Log.e(TAG, "invalid video width(" + width + ") or height(" + height + ")"); return; } mIsVideoSizeKnown = true; mVideoWidth = width; mVideoHeight = height; if (mIsVideoReadyToBePlayed && mIsVideoSizeKnown) { startVideoPlayback(); } } public void onPrepared(MediaPlayer mediaplayer) { Log.d(TAG, "onPrepared called"); mIsVideoReadyToBePlayed = true; if (mIsVideoReadyToBePlayed && mIsVideoSizeKnown) { startVideoPlayback(); } } public void surfaceChanged(SurfaceHolder surfaceholder, int i, int j, int k) { Log.d(TAG, "surfaceChanged called"); } public void surfaceDestroyed(SurfaceHolder surfaceholder) { Log.d(TAG, "surfaceDestroyed called"); } public void surfaceCreated(SurfaceHolder holder) { Log.d(TAG, "surfaceCreated called"); playVideo(extras.getInt(MEDIA)); } @Override protected void onPause() { super.onPause(); releaseMediaPlayer(); doCleanUp(); } @Override protected void onDestroy() { super.onDestroy(); releaseMediaPlayer(); doCleanUp(); } private void releaseMediaPlayer() { if (mMediaPlayer != null) { mMediaPlayer.release(); mMediaPlayer = null; } } private void doCleanUp() { mVideoWidth = 0; mVideoHeight = 0; mIsVideoReadyToBePlayed = false; mIsVideoSizeKnown = false; } private void startVideoPlayback() { Log.v(TAG, "startVideoPlayback"); holder.setFixedSize(mVideoWidth, mVideoHeight); mMediaPlayer.start(); } } I think the above message is due to Null pointer exception , however I may be false. I am unable to find where the error is . So , Please someone help me out .

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  • How to check null objects in jQuery

    - by Prashant
    I am using jQuery, I want to check existence of an element in my page. I have done following code, but its not working? if ($("#btext" + i) != null){ //alert($("#btext" + i).text()); $("#btext" + i).text("Branch " + i); } Please tell me what will be the right code? Thanks

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  • Elegant check for null and exit in C#

    - by aip.cd.aish
    What is an elegant way of writing this? if (lastSelection != null) { lastSelection.changeColor(); } else { MessageBox.Show("No Selection Made"); return; } changeColor() is a void function and the function that is running the above code is a void function as well.

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  • NetBeans IDE 7.3 Knows Null

    - by Geertjan
    What's the difference between these two methods, "test1" and "test2"? public int test1(String str) {     return str.length(); } public int test2(String str) {     if (str == null) {         System.err.println("Passed null!.");         //forgotten return;     }     return str.length(); } The difference, or at least, the difference that is relevant for this blog entry, is that whoever wrote "test2" apparently thinks that the variable "str" may be null, though did not provide a null check. In NetBeans IDE 7.3, you see this hint for "test2", but no hint for "test1", since in that case we don't know anything about the developer's intention for the variable and providing a hint in that case would flood the source code with too many false positives:  Annotations are supported in understanding how a piece of code is intended to be used. If method return types use @Nullable, @NullAllowed, @CheckForNull, the value is considered to be "strongly possible to be null", as well as if the variable is tested to be null, as shown above. When using @NotNull, @NonNull, @Nonnull, the value is considered to be non-null. (The exact FQNs of the annotations are ignored, only simple names are checked.) Here are examples showing where the hints are displayed for the non-null hints (the "strongly possible to be null" hints are not shown below, though you can see one of them in the screenshot above), together with a comment showing what is shown when you hover over the hint: There isn't a "one size fits all" refactoring for these various instances relating to null checks, hence you can't do an automated refactoring across your code base via tools in NetBeans IDE, as shown yesterday for class member reordering across code bases. However, you can, instead, go to Source | Inspect and then do a scan throughout a scope (e.g., current file/package/project or combinations of these or all open projects) for class elements that the IDE identifies as potentially having a problem in this area: Thanks to Jan Lahoda, who reports that this currently also works in NetBeans IDE 7.3 dev builds for fields but that may need to be disabled since right now too many false positives are returned, for help with the info above and any misunderstandings are my own fault!

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  • WHERE x = @x OR @x IS NULL

    - by steveh99999
    Every SQL DBA and developer should read the blog of MVP Erland Sommarskog – but particularly  his article on dynamic search conditions in T-SQL. I’ve linked above to his SQL 2005 article but his 2008 version is also a must-read. I seem to regularly come across uses of the SQL in the title above… Erland’s article explains in detail why this is inefficient, but I came across a nice example recently… A stored procedure contained the following code :- WHERE @Name is null or [Name] like @Name as a nonclustered index exists on the Name column, you might assume this would be handled efficiently by SQL Server. However, I got the following output from SET STATISTICS IO Table 'xxxxx'. Scan count 15, logical reads 47760, physical reads 9, read-ahead reads 13872, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0. Note the high number of logical reads… After a bit of investigation, we found that @Name could never actually be set to NULL in this particular example. ie the @x IS NULL was spurious… So, we changed the call to WHERE  [Name] like @Name Now, how much more efficient is this code ? Table 'xxxxx'. Scan count 3, logical reads 24, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0 A nice easy win in this case…… a full index scan has been replaced by a significantly more efficient index seek. I managed to recreate the same behaviour on Adventureworks – here’s a quick query to demonstrate :- USE adventureworks SET STATISTICS IO ON DECLARE @id INT = 51721 SELECT * FROM Sales.SalesOrderDetail WHERE @id IS NULL OR salesorderid = @id SELECT * FROM Sales.SalesOrderDetail WHERE salesorderid = @id Take a look at the STATISTICS IO output and compare the actual query plans used to prove the impact of  WHERE @id IS NULL. And just to follow some of Erland’s advice – here’s how you could get similar performance if it was possible that @id could actually sometimes contain NULL. DECLARE @sql NVARCHAR(4000), @parameterlist NVARCHAR(4000) DECLARE @id INT = 51721 – or change to NULL to prove query is functionally correct SET @sql = 'SELECT * FROM Sales.SalesOrderDetail WHERE 1 = 1' IF @id IS NOT NULL SET @sql = @sql + ' AND salesorderid = @id' IF @id IS NULL SET @sql = @sql + ' AND salesorderid IS NULL' SET @parameterlist = '@id INT' EXEC sp_executesql @sql, @parameterlist,@id Sometimes I think we focus too much on hardware and SQL Server configuration – when really the answer is focus on writing efficient SQL.

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  • handle null values for string when implementing IXmlSerializable interface

    - by user208081
    I have the following class that implements IXmlSerializable. When implementing WriteXml(), I need to handle the case where the string members of this class may be null values. What is the best way of handling this? Currently, I am using the default constructor in which all the string properties are initialized to empty string values. This way, when WriteXml() is called, the string will not be null. One other way I could do this is check using String.IsNullOrEmpty before writing each string in xml. Any suggestions on how I can improve this code? using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Xml.Serialization; using System.Globalization; namespace TCS.Common.InformationObjects { public sealed class FaxSender : IXmlSerializable { #region Public Constants private const string DEFAULT_CLASS_NAME = "FaxSender"; #endregion Public Constants #region Public Properties public string Name { get; set; } public string Organization { get; set; } public string PhoneNumber { get; set; } public string FaxNumber { get; set; } public string EmailAddress { get; set; } #endregion Public Properties #region Public Methods #region Constructors public FaxSender() { Name = String.Empty; Organization = String.Empty; PhoneNumber = String.Empty; FaxNumber = String.Empty; EmailAddress = String.Empty; } public FaxSender(string name, string organization, string phoneNumber, string faxNumber, string emailAddress) { Name = name; Organization = organization; PhoneNumber = phoneNumber; FaxNumber = faxNumber; EmailAddress = emailAddress; } #endregion Constructors #region IXmlSerializable Members public System.Xml.Schema.XmlSchema GetSchema() { throw new NotImplementedException(); } public void ReadXml(System.Xml.XmlReader reader) { throw new NotImplementedException(); } public void WriteXml(System.Xml.XmlWriter xmlWriter) { try { // <sender> xmlWriter.WriteStartElement("sender"); // Write the name of the sender as an element. xmlWriter.WriteElementString("name", this.Name.ToString(CultureInfo.CurrentCulture)); // Write the organization of the sender as an element. xmlWriter.WriteElementString("organization", this.Organization.ToString(CultureInfo.CurrentCulture)); // Write the phone number of the sender as an element. xmlWriter.WriteElementString("phone_number", this.PhoneNumber.ToString(CultureInfo.CurrentCulture)); // Write the fax number of the sender as an element. xmlWriter.WriteElementString("fax_number", this.FaxNumber.ToString(CultureInfo.CurrentCulture)); // Write the email address of the sender as an element. xmlWriter.WriteElementString("email_address", this.EmailAddress.ToString(CultureInfo.CurrentCulture)); // </sender> xmlWriter.WriteEndElement(); } catch { // Rethrow any exceptions. throw; } } #endregion IXmlSerializable Members #endregion Public Methods } }

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  • Check if an object is defined in html

    - by Manikanta
    In HTML, I have an object tag as follows: <OBJECT ID="objectid" CLASSID="some-class-id" CODEBASE="some-codebase"> I have written a function in JavaScript to access this object. I checked the null value as follows: if(objectid==null){-----} i want to check if the object is undefined or is empty. Do we have any functions to check so?

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  • Check constraint over two columns

    - by Rippo
    I want to add a Check Constraint to a table for server 2005 but cannot work it out. MemberId ClubId MeetingId 1 100 10 2 100 10 3 100 10 7 101 10 <-This would throw a check constraint 1 100 11 2 100 11 I do not want to have more than one ClubId for a single MeetingId Basically a ClubId can only belong to a single MeetingId but can have more than one member assigned. How do I achieve this?

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  • jQuery getJson returning null

    - by Adam
    I'm trying to use this api that lets you reference an exact text, but the getJson does not seem to be working, it's just returning null. $.getJSON('http://api.biblia.com/v1/bible/content/KJV.json?key=MYAPIKEY=John+3:16-18&style=bibleTextOnly', function(data) { alert(data); }); I just took the key out, i've been testing it with my real api key, and it works fine when i just visit the url. is there anything else i need to do to make it work? This is what you get from the url when you have an api key in the url: {"text":"For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. For God sent not his Son into the world to condemn the world; but that the world through him might be saved. He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God."}

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  • Android 2.1 View's getDrawingCache() method always returns null

    - by Impression
    Hello, I'm working with Android 2.1 and have the following problem: Using the method View.getDrawingCache() always returns null. Example code: public void onCreate(final Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); final View view = findViewById(R.id.ImageView01); view.setDrawingCacheEnabled(true); view.buildDrawingCache(); final Bitmap bmp = view.getDrawingCache(); System.out.println(bmp); } I've already tried different ways to configure the View object for generating the drawing cache (e.g. View.setWillNotDraw(boolean) and View.setWillNotCacheDrawing(boolean)), but nothing works. What is the right ways, or what do I wrong?

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  • Null-coalescing operator and operator && in C#

    - by abatishchev
    Is it possible to use together any way operator ?? and operator && in next case: bool? Any { get { var any = this.ViewState["any"] as bool?; return any.HasValue ? any.Value && this.SomeBool : any; } } This means next: if any is null then this.Any.HasValue return false if any has value, then it returns value considering another boolean property, i.e. Any && SomeBool

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  • Null Pointer Exception on a 2D array (Java)

    - by user315156
    I have a class, "Tetris", in which one of the instance variables is "board". "board" is 2D array of Color objects. Upon the creation of a tetris object I call a method that sets the dimensions of board and then sets all of the Color objects to be the Default value, that is to say, Color.blue. public Tetris(int rows, int cols){ this.rows = rows; this.cols = cols; reset(rows, cols); } public void reset(int rows, int cols){ Color[][] board = new Color[rows][cols]; for(int i = 0; i Unfortunately, when I run the code (which obviously has not been posted in its entirety) I get a null pointer exception on the line: board[i][j] = DEFAULT_COLOR; // Color.blue; //DEFAULT-COLOR. Is there anything obviously wrong with what I am doing? (Sorry if there are glaring format issues, this is my first time on Stack Overflow)

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