ContainerControl.ActiveControl Property

 

Gets or sets the active control on the container control.

Namespace:   System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

<BrowsableAttribute(False)>
Public Property ActiveControl As Control

Property Value

Type: System.Windows.Forms.Control

The Control that is currently active on the ContainerControl.

Exception Condition
ArgumentException

The Control assigned could not be activated.

The ActiveControl property activates or retrieves the active control on the container control.

In order to receive a valid value from this property, the object that calls it must either contain or be contained in the control it is calling. If one form tries to call another form's ActiveControl properties, it will receive an undefined value. In this case, you need to define your own communication mechanism between the forms to pass this data.

The following code example inherits from the ScrollableControl class and implements the IContainerControl interface. Implementation is added to the ActiveControl property and the ActivateControl method.

Imports System
Imports System.Windows.Forms
Imports System.Drawing

   Public Class MyContainerControl
      Inherits ScrollableControl
      Implements IContainerControl 

      Private myActiveControl As Control

      Public Sub New()
         ' Make the container control Blue so it can be distinguished on the form.
         Me.BackColor = Color.Blue

         ' Make the container scrollable.
         Me.AutoScroll = True
      End Sub 

      ' Add implementation to the IContainerControl.ActiveControl property.
      Public Property ActiveControl() As Control Implements IContainerControl.ActiveControl
         Get
            Return Me.myActiveControl
         End Get

         Set
            ' Make sure the control is a member of the ControlCollection.
            If Me.Controls.Contains(value) Then
               Me.myActiveControl = value
            End If
         End Set
      End Property

      ' Add implementation to the IContainerControl.ActivateControl(Control) method.
      public Function ActivateControl(active As Control) As Boolean Implements IContainerControl.ActivateControl
         If Me.Controls.Contains(active) Then
            ' Select the control and scroll the control into view if needed.
            active.Select()
            Me.ScrollControlIntoView(active)
            Me.myActiveControl = active
            Return True
         End If
         Return False
      End Function 

   End Class  

.NET Framework
Available since 1.1
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