Convert C# statement body lambda to VB

Question

It appears that VB in VS8 doesn't support/convert lambda expressions with a statement body. I'm using them in my C# application, but now must convert it to VB.

I'm creating a whole bunch of controls dynamically, and I want to be able to give them event handlers on the fly. This is so I can build a dynamic user interface from a database. In the following code I'll create a form and a checkbox, make the checkbox control the form's visibility, add a few method handlers to the form, and then add the newly created checkbox to a pre-existing form/panel/etc. Handlers for the form, for instance, affect the checkbox:

  // Inside some loop creating a lot of these forms and matching checkboxes
      Form frmTemp = frmTestPanels[i];  // New form in array
      CheckBox chkSelectPanel;          // New checkbox that selects this panel
      chkSelectPanel = new CheckBox();
      chkSelectPanel.Text = SomeName;   // Give checkbox a label
      chkSelectPanel.Click += (ss, ee) =>  // When clicked
      {
          label1.Text = SomeName;       // Update a label
          if (chkSelectPanel.Checked)   // Show or hide the form
          {
              frmTemp.Show();
          }
          else
          {
              frmTemp.Hide();
          }
      };

      frmTemp.VisibleChanged += (ss, ee) =>  // When form visibility changes
      {
          chkSelectPanel.Checked = frmTemp.Visible;  // Reflect change to checkbox
          ConfigurationFileChanged = true;   // Update config file later
      };

      frmTemp.FormClosing += (ss, ee) =>     // When the form closes
      {   // We're only pretending to close the form - it'll sit around until needed
          chkSelectPanel.Checked = false;    // Update the checkbox
          frmTemp.Hide();                    // Hide the form
          ee.Cancel = true;                  // Cancel the close
      };

      flpSelectGroup.Controls.Add(chkSelectPanel); // Add checkbox to flow layout panel
  // End of loop creating a bunch of these matching forms/checkboxes

Of course, I'm getting the conversion error, "VB does not support anonymous methods/lambda expressions with a statement body"

I really liked the ability to create everything on the fly, and then let the objects handle themselves - I don't need to add any special functions that figure out which form is giving the close event so it can search for the right checkbox and update the checkbox - It Just Works (TM).

Unfortunately it needs to be converted to VB.

What is the best way to convert lambda/anonymous statement bodies into something that will work in VB, especially when one needs to create many of them?

-Adam

(http://stackoverflow.com/questions/249314/what-do-you-think-of-multiline-lambdas-in-vb-10) — Marc Gravell, Oct 14 '09 at 19:50
Heh. I think the VB developer this is going to is still using VS2005 as it is (ie, I'm going to have other problems, no doubt). I'm note sure if there are requirements that would prevent moving to VS10, but hopefully there's another answer should this option be unavailable. — Adam Davis, Oct 14 '09 at 19:53

Kamarey · Accepted Answer · 2010-03-07T09:29:55.510

4

Wait for the nearest release of .NET 4, it will support things like this in VB. Don't see other alternative.

Ugly alternatives are:

This work, but you can use a single statement in a function.

AddHandler Me.Click, Function(o, e) MessageBox.Show("text")

Create some regular Sub Foo

Public Sub Foo(ByVal o As Object, ByVal e As EventArgs)
     MessageBox.Show("text")
End Sub

and use AddHandler to bind it to an event

AddHandler Me.Click, AddressOf Foo

edited Mar 07 '10 at 09:29

answered Oct 14 '09 at 19:48

Kamarey

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"Don't see other alternative." Well I'm sure there's a way to duplicate the functionality, I just expect it's going to be messy. Since I am not very familiar with it, though, I'm hoping that someone else will have a better idea than the ugly implementation I think I might have to do. – Adam Davis Oct 14 '09 at 19:55
Thanks, those ideas are pretty much what I expected. – Adam Davis Oct 14 '09 at 20:22

score 1 · Answer 2 · answered Oct 14 '09 at 20:38

1

Could you make a new class that accepts the Form in the constructor and has chkSelectPanel as a field, allowing you to use instance methods as your event handlers?

answered Oct 14 '09 at 20:38

dahlbyk

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Convert C# statement body lambda to VB

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