ReceiveAsync Issues - WPF Discussion Boards

Re: How to check duplicate data in listbox.itemtemplate

18-Apr-11 5:03

In the code where you bind the property of the textbox, write some code to check if if the text box value is already contained within the collection that binds to the listbox. You can then handle the duplicate as you like.

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Rocky2318-Apr-11 23:03

Rocky23

18-Apr-11 23:03

hi, i have used the code like the way u said, still its not running the code inside it(if Condition)...

Directive lstdir = new Directive { DirectiveName = txtDirectiveName.Text.Trim(), DirectiveDescription = txtDirectiveDescription.Text.Trim() };
if (txtDirectiveName.Text != lstdir.DirectiveName && txtDirectiveDescription.Text != lstdir.DirectiveDescription)
{
MessageBox.Show("Execute");
}

else MessageBox.Show("Duplicate Data")

Bind a UserControl string array property to containing window

Jean-Louis Leroy17-Apr-11 23:08

Jean-Louis Leroy

17-Apr-11 23:08

Hello,

I have a UserControl that exposes a Selection property:

public partial class FeatureSelectionControl : UserControl
{

  public string[] Selection
  {
    get { return (string[])GetValue(SelectionProperty); }
    set { SetValue(SelectionProperty, value); }
  }

  public static readonly DependencyProperty SelectionProperty =
      DependencyProperty.Register("Selection", typeof(string[]), typeof(FeatureSelectionControl), new UIPropertyMetadata(new string[] { }));

I want to use it in a window and bind the control's property to one of the window's properties:

<Window Name="Window" ...>
    <local:FeatureSelectionControl Selection="{Binding ElementName=Window,Path=CustomerGroups}" ...>
    </local:FeatureSelectionControl>

Code behind:

public partial class WindowCounterpartyGroupRiskReview : Window
{
  public WindowCounterpartyGroupRiskReview()
  {
    CustomerGroups = new string[] { };
    InitializeComponent();
  }

  public string[] CustomerGroups { get; set; }

This crashes with a "first chance exception of type 'System.NullReferenceException' occurred in PresentationFramework.dll Additional information: Object reference not set to an instance of an object". STack trace is:

	PresentationFramework.dll!System.Windows.Markup.BamlRecordReader.ProvideValueFromMarkupExtension(System.Windows.Markup.MarkupExtension markupExtension = null, object obj = {System.Windows.Markup.BamlCollectionHolder}, object member = null) + 0x52 bytes	
 	PresentationFramework.dll!System.Windows.Markup.BamlRecordReader.ReadPropertyArrayEndRecord() + 0x5f bytes	
 	PresentationFramework.dll!System.Windows.Markup.BamlRecordReader.ReadRecord(System.Windows.Markup.BamlRecord bamlRecord) + 0x636 bytes	
 	PresentationFramework.dll!System.Windows.Markup.BamlRecordReader.Read(bool singleRecord = false) + 0x1c bytes	
 	PresentationFramework.dll!System.Windows.Markup.TreeBuilderBamlTranslator.ParseFragment() + 0xc9 bytes	
 	PresentationFramework.dll!System.Windows.Markup.TreeBuilder.Parse() + 0xf bytes	
 	PresentationFramework.dll!System.Windows.Markup.XamlReader.LoadBaml(System.IO.Stream stream, System.Windows.Markup.ParserContext parserContext, object parent, bool closeStream) + 0xc7 bytes	
 	PresentationFramework.dll!System.Windows.Application.LoadComponent(object component, System.Uri resourceLocator) + 0x16e bytes	
>	CRRT.exe!CRRT.WindowCounterpartyGroupRiskReview.InitializeComponent() Line 1 + 0xb bytes	C#

However, when I change my code and make the property a mere string, I don't get an exception and everything works as expected.

Any idea ?

Re: Bind a UserControl string array property to containing window

Jean-Louis Leroy17-Apr-11 23:41

Jean-Louis Leroy

17-Apr-11 23:41

Ok I found the solution here: use a List<string> instead of a string[].

ReceiveAsync Issues

veggieCoder15-Apr-11 8:13

veggieCoder

15-Apr-11 8:13

Hello,

I'm having some difficulty retrieving JSON formatted data returned from a remote server. I'm using Silverlight 4 in VS 2010. My code is as follows:

byte[] response = new byte[32768]; 
SocketAsyncEventArgs e = new SocketAsyncEventArgs(); 
e.SetBuffer(response, 0, response.Length); 
soc.ReceiveAsync(e); 
//System.Threading.Thread.Sleep(4000); 
string data = Encoding.UTF8.GetString(e.Buffer, e.Offset, e.BytesTransferred).Trim(new char[] { '\0' });

If I uncomment the call to Sleep for 4 or 5 seconds, then my string variable "data" populates consistently. However, if I don't Sleep, then after a few times of receiving updates, the variable "data" is consistently empty (although there is data in the buffer). Basically, I have to slow the whole process down in order to get my updates. That's not an acceptable solution though, as I'm dealing with market data which needs to be processed in real-time.

Incidentally, nearly identical code works without the call to Sleep in a console app I wrote against the same remote server. In that case, the following works perfectly:

byte[] snapBytes = new byte[32768]; 
soc.Receive(snapBytes); 
String data = Encoding.ASCII.GetString(snapBytes).Trim(new char[] { '\0' });

Thanks in advance for any thoughts or ideas.

Re: ReceiveAsync Issues

SledgeHammer0115-Apr-11 10:05

SledgeHammer01

15-Apr-11 10:05

Well, yeah...

Do you understand what the "Async" in "ReceiveAsync" is supposed to do? Its an asynchronous function meaning its non blocking. So when you call soc.ReceiveAsync() it IMMEDIATELY goes to the next line and the buffer will be filled to a random length depending on millions of things.

This is used so you don't hang your GUI and don't need to handle multi-threading yourself.

You need to wait til the call is *really* done. For instance, by subscribing to the SocketAsyncEventArgs.Completed event Smile | :)

PRISM in Silverlight

NTheOne15-Apr-11 0:30

NTheOne

15-Apr-11 0:30

Hello,

Anyone can tell me advantages using PRISM in Silverlight.
And Which design pattern is suitable for PRISM....Its MVVM?

Thanks & Regards...

Re: PRISM in Silverlight

Tarun.K.S15-Apr-11 0:59

Tarun.K.S

15-Apr-11 0:59

Check out these links :

http://www.grumpydev.com/2009/07/04/why-shouldn%E2%80%99t-i-use-prism/[^]

http://msdn.microsoft.com/en-us/magazine/cc785479.aspx[^]

Lastly a full detail about it :
http://msdn.microsoft.com/en-us/library/gg430865%28PandP.40%29.aspx[^]

Good luck!

People with high attitude deserve the standing ovation of our highest finger!

My Blog![^]

Re: PRISM in Silverlight

Pete O'Hanlon15-Apr-11 1:59

15-Apr-11 1:59

Code Project author and Prism team member Karl Shifflett has literally written the book on Prism development. Check out his blog[^], and order the book.

Forgive your enemies - it messes with their heads

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Re: PRISM in Silverlight

Abhinav S15-Apr-11 17:58

15-Apr-11 17:58

MVVM does complement Prism.

Prism give you an opportunity to work in a more decoupled UI / code environment while giving you necessary framework features to call these framework features.

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WPF PopUp control

Rahul Chitte14-Apr-11 1:59

Rahul Chitte

14-Apr-11 1:59

Hi,

I have just started learning WPF and exploring more on WPF controls.

Can any one help how to display popup? I have used TextBlock under popup control as below :

<pre> <Popup StaysOpen="True">
<TextBlock Name="txtBlock1">
This is simple PopUp in WPF..
</TextBlock>
</Popup></pre>

But how to trigger this popup?

Thanks and regards,
Rahul Chitte

Pete O'Hanlon14-Apr-11 2:20

14-Apr-11 2:20

Popups are shown with the IsOpen method.

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Forgive your enemies - it messes with their heads

Ian Shlasko14-Apr-11 3:19

Ian Shlasko

14-Apr-11 3:19

Two ways:

1) Give it a name (The Popup itself, not just the TextBlock), and open it in the code-behind

2) (The preferred method) Bind the Popup's IsOpen property to something else, such as a toggle button or a boolean field on your underlying model.

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Author of the Guardians Saga (Sci-Fi/Fantasy novels)

Abhinav S14-Apr-11 3:32

14-Apr-11 3:32

This sample [^]could help you out.

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Tarun.K.S14-Apr-11 3:50

Tarun.K.S

14-Apr-11 3:50

That's a good example! Thumbs Up | :thumbsup:

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My Blog![^]

Abhinav S14-Apr-11 4:05

Another Dummies question (sorry)

14-Apr-11 4:05

Thank you Tarun.

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Johnny J.14-Apr-11 0:53

Johnny J.

14-Apr-11 0:53

OK; I have digested the depressing news I got in my "Data Access for Dummies" thread below and accepted that I need to create a Silverlight 4 client app and a WCF host service that supplies the data.

SFSG!

Of course, I want to create a common class library containing the DTO class definitions so that the host and the client can share the same definitions.

BUT!!! If I create a Silverlight class library, I can't use Ado objects to access the db (which I want to do), and if I create a "normal" windows class library, I can't reference it in my Silverlight client app.

So how can I do that???

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-----
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Pete O'Hanlon14-Apr-11 1:33

14-Apr-11 1:33

Do you know how WCF works? I'm not being funny, I'm just trying to find a common basepoint here. If you have your Silverlight app needing to know about Ado types, then you have just put a hard dependency in which means that your service could not be consumed by other types of systems (such as Java ones) that have no knowledge of the Ado types.

You create your model as a DataContract. Here's an example:

namespace WcfServer
{
    using System;
    using System.Runtime.Serialization;

    /// <summary>
    /// The contract that defines the customer structure.
    /// </summary>
    [DataContract]
    public class Customer
    {
        /// <summary>
        /// Gets or sets the customer forename.
        /// </summary>
        [DataMember]
        public string Forename { get; set; }

        /// <summary>
        /// Gets or sets the customer surname.
        /// </summary>
        [DataMember]
        public string Surname { get; set; }

        /// <summary>
        /// Gets or sets the date of birth of the customer
        /// </summary>
        [DataMember]
        public DateTime DateOfBirth { get; set; }

        /// <summary>
        /// Gets the Id of the customer.
        /// </summary>
        [DataMember]
        public int Id { get; internal set; }
    }
}

As you can see, it's POCO. Now, the point here is that you don't add this as a class library into your Silverlight application. What you do, is import the service reference into your Silverlight application, so it gets access to the contract (and all the other gubbins it needs, such as the OperationContract). You now have a nice separation in place which means that you can leverage things such as web farms to manage scalability of your service.

As you are new at this, I would recommend buying a book and reading up on this. There's a lot to it, and it's well worth the investment. The book I usually recommend for Silverlight is Silverlight 4 Unleashed[^] by MVP and Mix speaker, Laurent Bugnion.

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Forgive your enemies - it messes with their heads

Johnny J.14-Apr-11 2:26

Johnny J.

14-Apr-11 2:26

All this is quite new to me, I've never used neither Silverlight nor WCF before and my knowledge about those techniques is quite limited, hence the stupid questions.

Thanks for having patience with me, though. I get your point above to a certain point. But isn't it so (with reference to your example) that the Customer class with its DataContract attributes needs to be defined and have identical definitions on both sides of the WCF wall? That is at least what I seem to recall having read somewhere.

Thanks for the book recommendation. I actually ordered that very book yesterday. But since it's going to take some time for it to arrive, I thought I'd get going by asking stupid questions in this Forum in the meanwhile... Big Grin | :-D

Pete O'Hanlon14-Apr-11 2:52

14-Apr-11 2:52

Johnny J. wrote:
But isn't it so (with reference to your example) that the Customer class with
its DataContract attributes needs to be defined and have identical definitions
on both sides of the WCF wall?

Yes, but when you import the service reference, that comes with it. In other words, the proxy implementation that your Silverlight service calls is created for you - that's cool.

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Johnny J.14-Apr-11 2:55

Johnny J.

14-Apr-11 2:55

So when you change somthing in your service, you need to refresh or delete/readd your service reference?

Pete O'Hanlon14-Apr-11 3:19

14-Apr-11 3:19

Yes. You import the contract, which creates a proxy implementation.

I'm not a stalker, I just know things. Oh by the way, you're out of milk.

Forgive your enemies - it messes with their heads