Application.AddMessageFilter(IMessageFilter) Method

public:
 static void AddMessageFilter(System::Windows::Forms::IMessageFilter ^ value);

public static void AddMessageFilter (System.Windows.Forms.IMessageFilter value);

public static void AddMessageFilter (System.Windows.Forms.IMessageFilter? value);

static member AddMessageFilter : System.Windows.Forms.IMessageFilter -> unit

Public Shared Sub AddMessageFilter (value As IMessageFilter)

Parameters

Examples

The following code example creates a message filter called TestMessageFilter. This filter blocks all messages relating to the left mouse button. Before you can use a message filter, you must provide an implementation for the IMessageFilter interface.

// Creates a  message filter.
ref class TestMessageFilter: public IMessageFilter
{
public:
   [SecurityPermission(SecurityAction::LinkDemand, Flags = SecurityPermissionFlag::UnmanagedCode)]
   virtual bool PreFilterMessage( Message % m )
   {
      
      // Blocks all the messages relating to the left mouse button.
      if ( m.Msg >= 513 && m.Msg <= 515 )
      {
         Console::WriteLine( "Processing the messages : {0}", m.Msg );
         return true;
      }

      return false;
   }

};

// Creates a  message filter.
public class TestMessageFilter : IMessageFilter
{
    public bool PreFilterMessage(ref Message m)
    {
        // Blocks all the messages relating to the left mouse button.
        if (m.Msg >= 513 && m.Msg <= 515)
        {
            Console.WriteLine("Processing the messages : " + m.Msg);
            return true;
        }
        return false;
    }
}

' Creates a message filter.
<SecurityPermission(SecurityAction.LinkDemand, Flags := SecurityPermissionFlag.UnmanagedCode)> _
Public Class TestMessageFilter
    Implements IMessageFilter

    <SecurityPermission(SecurityAction.Demand)> _
    Public Function PreFilterMessage(ByRef m As System.Windows.Forms.Message) _
    As Boolean Implements IMessageFilter.PreFilterMessage
        ' Blocks all the messages relating to the left mouse button.
        If ((m.Msg >= 513) And (m.Msg <= 515)) Then
            Console.WriteLine("Processing the messages : " & m.Msg)
            Return True
        End If
        Return False
    End Function
End Class

Remarks

Use a message filter to prevent specific events from being raised or to perform special operations for an event before it is passed to an event handler. Message filters are unique to a specific thread.

To prevent a message from being dispatched, the value parameter instance that you pass to this method must override the PreFilterMessage method with the code to handle the message. The method must return false.

Applies to