Add Shown event to a UserControl in C#

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Hi,

I have a user control and i need to edit some things on the event similar to "Shown" with forms.

I tried the following but that does not work:

Added the following line to the designer:

C#

this.Shown += this.HandleControlShown

and added this to the class of the control:

C#

public event EventHandler Shown;

private void HandleControlShown(object sender, EventArgs e)
{
    this.OnShown(EventArgs.Empty);
    //code to execute on shown event goes here.... but does not execute
}

protected virtual void OnShown(EventArgs e)
{
    EventHandler handler = this.Shown;
    if (handler != null)
    {
        handler(this, e);
    }
}

Where am i doing something wrong?

Posted 6-Nov-12 2:47am

pieterjann

Updated 13-Aug-19 5:05am

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__John_ 6-Nov-12 8:58am

UserControl does not have a Shown event, but it does have a Load event.

pieterjann 6-Nov-12 9:04am

I know, but I need the Shown event, the Load event is only casted once. Isn't there a way to add the Shown event manually?

__John_ 6-Nov-12 9:19am

You can add your own event but you would need some trigger to fire it.
What do you mean by Shown? i.e. Bring to front? Paint? Or something else?

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Sanjay K. Gupta · Answer 1 · 2012-11-06T03:20:00

Eevent declaration code, may be helpful to you.

C#

//declare a delegate
public delegate ShownEventHandler(string args);

public event ShownEventHandler Shown;
private void HandleControlShown(object sender, EventArgs e)
{
 if(this.Shown!=null)
 {
    this.Shown(String.Empty/*your args*/);
    //code to execute on shown event goes here.... but does not execute
 }
}

Jens Madsen, Højby · Answer 2 · 2019-08-13T05:05:00

OK, this is old, but as I often face issues concerning 'stuff' that needs a visible window/window handle, I use a System.Windows.Forms.Timer like this:

(This UserControl hosts a native NamespaceTreeControl that needs a visible handle to initialize)

VB

   Private Sub NamespaceTreeControlLite_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
            Dim tmr As New Timer() With {.Interval = 100, .Enabled = True}
            AddHandler tmr.Tick, AddressOf WaitForUCTRLVisible
End Sub


  Private Sub WaitForUCTRLVisible(sender As Object, e As EventArgs)
' Do stuff here that require .Visible=True
            If Me.Visible Then

                Try
                    Marshal.ThrowExceptionForHR(Me.NamespaceTreeBase1.Initialize(Me, Me.ClientRectangle))
                    Me.SetRootPath()
                Catch ex As Exception
                    MsgBox(ex.ToString(), MsgBoxStyle.Critical)
                End Try

                Dim tmr = TryCast(sender, Timer)
                If Not tmr Is Nothing Then
                    tmr.Dispose()
                    tmr = Nothing
                End If
            End If
        End Sub

(It also releaves the PIA of having global variables that are used for this sole purpose...)

Add Shown event to a UserControl in C#

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