How to get the focus of a text box that is anywhere (such as: on a SplitContainer or any control that contains other controls)

Hi @Mansour_Dalir ,

You should check the type of the ActiveControl before modifying its text.

If the ActiveControl is a ContainerControl (like a SplitContainer, TabControl, or Panel), use a helper function to retrieve the actual focused child control.

    Private Sub ToolStripButton1_Click(sender As Object, e As EventArgs) Handles ToolStripButton1.Click
        If TypeOf Me.ActiveControl Is TextBox Then
            Dim activeTextBox As TextBox = CType(Me.ActiveControl, TextBox)
            activeTextBox.Text += "A"
        ElseIf TypeOf Me.ActiveControl Is ContainerControl Then
            Dim focusedControl As Control = GetFocusedControl(Me.ActiveControl)
            If TypeOf focusedControl Is TextBox Then
                Dim activeTextBox As TextBox = CType(focusedControl, TextBox)
                activeTextBox.Text += "A"
            End If
        End If
    End Sub
    Private Function GetFocusedControl(container As Control) As Control
        Dim activeControl As Control = container
        While TypeOf activeControl Is ContainerControl AndAlso CType(activeControl, ContainerControl).ActiveControl IsNot Nothing
            activeControl = CType(activeControl, ContainerControl).ActiveControl
        End While
        Return activeControl
    End Function

Best Regards.

Jiachen Li

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