how to set properties for a custom control (p.e. from system.windows.controls)

Question

Hello everybody,

I have added a progressbar as custom control from System.Windows.Control to my LightSwitch screen.
Now I want to set properties as "Minimum", "Maximum" and "Value", but do not know how to solve this.
I studied the forum but cannot see any proper solution.
Can anybody help me?

Thanks in advance.

Albert

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Albert Korstanje

Answer 1

Use the FindControl extension method to either set bindings for the ProgressBar or to subscribe a ControlAvailable event handler to get a reference to the ProgressBar.

Here's an example of how to set bindings:http://msdn.microsoft.com/en-us/library/gg406736.aspx

If you search for "FindControl" in the forums, you'll find many threads on how to use the ControlAvailable event.

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Justin Anderson, LightSwitch Development Team

Answer 2

Justin, Thanks.

I checked the information and came up with the following solution:

1) On the screen I defined a custom control "PrgBar" as System.Windows.Controls.Progressbar

2) Private WithEvents Pb As System.Windows.Controls.ProgressBar

3) in the "_InitializeDataWorkspace" routine:
          AddHandler Me.FindControl("PrgBar").ControlAvailable, AddressOf PrgBarAvailable

4)  Private Sub PrgBarAvailable(Sender As Object, e As ControlAvailableEventArgs)
          Pb = CType(e.Control, System.Windows.Controls.ProgressBar)
     End Sub

5) In some other routine:
         Pb.Minimum = 1      <----- gives error: "Invalid cross-thread access"
         Pb.Maximum = 100
         Pb.Value = 1

What is wrong with the definition of "Pb"?

Hope you can help

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Albert Korstanje

Answer 3

Albert try the following code (sorry for c#)
this.Application.Details.Dispatcher.BeginInvoke(() =>
{
Pb.Minimum = 1;                
Pb.Maximum = 100;
Pb.Value;
};

                

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rdk

Answer 4

Ralf almost has it right, but not quite. Since you are trying to modify properties of Silverlight controls, you have to be on the main thread (instead of the logic thread of the screen):

Dispatchers.Main.Invoke(Sub()
    Pb.Minimum = 1
    Pb.Maximum = 100
    Pb.Value = 1
End Sub)

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Justin Anderson, LightSwitch Development Team

Answer 5

Hello Justin,

Thanks for your reply.
Your solution is working OK, except that for "Dispatchers.Main.Invoke" I had to set it to: "Microsoft.LightSwitch.Threading.Dispatchers.Main.BeginInvoke":

            Microsoft.LightSwitch.Threading.Dispatchers.Main.BeginInvoke(
            Sub()
                Pb.Minimum = 1
                Pb.Maximum = 100
                Pb.Value = 1
            End Sub)

Thanks again for spending time in solving my problem.

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Albert Korstanje

Answer 6

Ralf,

Thanks for your reply that helped me solving the problem.
It toke some time because I was upgrading to Visual Studio 2010 Professional, which was not successful immediately. 

See the code in VB in my answer to Justin.

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Albert Korstanje