WinForm中DefWndProc、WndProc与IMessageFilter的区别

protected override void DefWndProc(ref Message m)
{
 ....
   base.DefWndProc(m);
}
  
protected override void WndProc(ref Message m);
{
 .....
   base.WndProc(m);
}

public class MessageFilter : IMessageFilter
{
 public bool PreFilterMessage(ref Message msg)
 {
   //识别消息并处理
  //return true;//吞掉消息，不派发
   return false;//进入下一步派发到对应窗口过程
 }
}
  
//在应用程序消息循环中加入消息过滤器
MessageFilter f = new MessageFilter(this.lbMsg);
Application.AddMessageFilter(f);

[StructLayout(LayoutKind.Sequential), SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
public struct Message
{
   private IntPtr hWnd;
   private int msg;
   private IntPtr wparam;
   private IntPtr lparam;
   private IntPtr result;
   public IntPtr HWnd { get; set; }
   public int Msg { get; set; }
   public IntPtr WParam { get; set; }
   public IntPtr LParam { get; set; }
   public IntPtr Result { get; set; }
   public object GetLParam(Type cls);
   public static Message Create(IntPtr hWnd, int msg, IntPtr wparam, IntPtr lparam);
   public override bool Equals(object o);
   public static bool operator !=(Message a, Message b);
   public static bool operator ==(Message a, Message b);
   public override int GetHashCode();
   public override string ToString();
}
  

//Declaring Type: System.Windows.Forms.Control //Assembly: System.Windows.Forms, Version=2.0.0.0 public static Control FromHandle(IntPtr handle);通过这种方式可以监测各消息的信息来自哪个控件。
public bool PreFilterMessage(ref Message msg)
{
   Control c = Control.FromHandle(msg.HWnd);
   if (c == null)
      System.Diagnostics.Debug.WriteLine("Filter:NULL" +"-" + msg.ToString());
   else
      System.Diagnostics.Debug.WriteLine("Filter:" +c.Name+"-"+ msg.ToString());
   return false;
}