C#

/// <summary>Operation for SHFileOperation</summary>
public enum SHFOOperation : int 
{
    /// <summary>Move the file(s)</summary>
    Move = 0x1,
    /// <summary>Copy the file(s)</summary>
    Copy = 0x2,
    /// <summary>Delete the file(s)</summary>
    Delete = 0x3,
    /// <summary>Rename the file(s)</summary>
    Rename = 0x4,
}

/// <summary>Flags for SHFileOperation</summary>
[Flags]
public enum SHFOFlags : int 
{
    /// <summary></summary>
    None = 0x000,

    /// <summary>Multiple destination files</summary>
    MultiDestFiles = 0x001,
    /// <summary>Confirm mouse actions</summary>
    ConfirmMouse = 0x002,
    /// <summary>Silent</summary>
    Silent = 0x004,
    /// <summary>Rename files on collision</summary>
    RenameOnCollision = 0x008,
    /// <summary>No confirmation</summary>
    NoConfirmation = 0x010,
    /// <summary>Return a mapping handle for renamed files</summary>
    WantMappingHandle = 0x020,
    /// <summary>Allow undo</summary>
    AllowUndo = 0x040,
    /// <summary>Files only (no folders)</summary>
    FilesOnly = 0x080,
    /// <summary>Simple progress bar</summary>
    SimpleProgress = 0x100,
    /// <summary>Don't confirm directory creation</summary>
    NoConfirmMkDir = 0x200,
    /// <summary>Don't display errors</summary>
    NoErrorUi = 0x400,
    /// <summary>Don't copy NTFS security attributes</summary>
    NoCopySecurity = 0x800,
}

public MyClass()
{
  if (DesignMode)
  {
    //add some extra stuff
    //Add a msgbox to popup maybe???
  }
  else 
  {
    //do some different stuff, so u can see the difference, change color or something
  }
  //do normal stuff
}

bool loaded = false;

protected override void OnLoad(EventArgs e){
  loaded = true;
  base.OnLoad(e);
}

public int SomeProperty {
  get {
    if (loaded & DesignMode) dosomethingelse();
    return someint;
  }
}