Delegates and Threads - Convert C# to VB.Net 1

[eatwork]

Hi everyone,
I am attempting to learn about threads and multithreading in VB.net and stumbled across a tutorial online. I was following until the article, which is in C# did this:

        // update the grid a thread safe fasion!
        MethodInvoker updateGrid = delegate
        {
          m_grid.DataSource = ds.Tables(0)
        }

Does anyone know what this is doing and how to translate this into vb.net? thank you

 

[jebenson]

No clue, but there a three excellent FAQs here on TekTips that cover Threading:

An Intro to Threading: faq796-5929
An Intro to Threading 2: Delegates faq796-6036
An Intro to Threading 3: Crossing thread boundries (and passing parameters) faq796-6056

Check those out and maybe your question will be answered.

I used to rock and roll every night and party every day. Then it was every other day. Now I'm lucky if I can find 30 minutes a week in which to get funky. - Homer Simpson

Arrrr, mateys! Ye needs ta be preparin' yerselves fer Talk Like a Pirate Day! Ye has a choice: talk like a pira

 

[eatwork]

This is the full function posted in the tutorial:

    private void CallBack(IAsyncResult ar)
    {
        // get the dataset as output
        DataSet ds = m_invokeMe.EndInvoke(ar);

        // update the grid a thread safe fasion!
        MethodInvoker updateGrid = delegate
        {
            m_grid.DataSource = ds.Tables[0];
        };

        if (m_grid.InvokeRequired)
            m_grid.Invoke(updateGrid);
        else
            updateGrid();
    }

 

[eatwork]

Thanks for the post jebenson,
I looked up the FAQ's you posted, although informative, I couldn't really see an answer to my question from there. But I will definately keep those in mind as a future reference. Thanks

 

[earthandfire]

This explains the purpose and usage of MeyhodInvoker and shows the VB.NET declaration:

http://msdn2.microsoft.com/en-us/library/system.windows.forms.methodinvoker.aspx

Hope this helps.

 

[eatwork]

Hi earthandFire,
thank you for the post. I took a look at the site you have provided, and I am still unable to understand the section where they set the method invoker = to a delegate. What is the purpose of the squigley brackets? Thanks

        // update the grid a thread safe fasion!
        MethodInvoker updateGrid = delegate
        {
            m_grid.DataSource = ds.Tables[0];
        };

 

[earthandfire]

Generally:

{ = BEGIN
} = END

In C-based languages, all functions (subs and functions in VB), method, properties, for loops, if statements etc. have there statements in braces. For example:

In VB

If a = 10 Then
b = 5
End If

C-type languages would use something like:
If (a=10)
{
b=5;
};

Hope this helps.

 

[ThatRickGuy]

eatwork, the reason for that code is to have the update to the m_grid object take place on the thread that owns it. I am not totally familiar with the C# syntax, I have a feeling that there may be a bit more code in that class that is relevant. Chiph is the local C#/VB.Net translation pro, and I know he is familiar with threading in both syntaxes.

If you have any questions regarding threading in VB.Net, I'd be glad to help as I can.

-Rick

VB.Net Forum forum796 forum855 ASP.NET Forum
I believe in killer coding ninja monkeys.

 

[eatwork]

Hi earthAndFire and ThatRickGuy,
Thank you for your posts. I was able to create a seperate function and create a seperate delegate to handle the code above, something to the effect of:

Private Delegate Sub doUpdateGrid(ByVal ds As DataSet)

Private Sub CallBack(ByVal ar As IAsyncResult)
 '// get the dataset as output
 Dim ds As DataSet = m_invokeMe.EndInvoke(ar)

 Dim updateGrid As doUpdateGrid = New doUpdateGrid(AddressOf updGrid)

 If (m_grid.InvokeRequired) Then
  Dim tag As IAsyncResult = m_grid.BeginInvoke(updateGrid, ds)
 Else
  updateGrid(ds)
 End If
End Sub

Private Sub updGrid(ByVal ds As dataset)
  m_grid.DataSource = ds.Tables(0)
End Sub

Thanks for your help. This threading subject is just hard for me to get my head around. Thanks for your help again.