C# Signature:

// This static method is required because legacy OSes do not support
// SetWindowLongPtr
public static IntPtr SetWindowLongPtr(HandleRef hWnd, int nIndex, IntPtr dwNewLong)
{
      if (IntPtr.Size == 8)
      return SetWindowLongPtr64(hWnd, nIndex, dwNewLong);
      else
      return new IntPtr(SetWindowLong32(hWnd, nIndex, dwNewLong.ToInt32()));
}

[DllImport("user32.dll", EntryPoint="SetWindowLong")]
private static extern int SetWindowLong32(HandleRef hWnd, int nIndex, int dwNewLong);

[DllImport("user32.dll", EntryPoint="SetWindowLongPtr")]
private static extern IntPtr SetWindowLongPtr64(HandleRef hWnd, int nIndex, IntPtr dwNewLong);

VB.NET Signature:

  <System.Runtime.InteropServices.DllImport("user32.dll", EntryPoint:="SetWindowLong")> _
  Private Shared Function SetWindowLong32(ByVal hWnd As IntPtr, <MarshalAs(UnmanagedType.I4)>nIndex As WindowLongFlags, ByVal dwNewLong As Integer) As Integer
  End Function

VB Signature:

  <System.Runtime.InteropServices.DllImport("user32.dll", EntryPoint:="SetWindowLongPtr")> _
  Private Shared Function SetWindowLongPtr64(ByVal hWnd As IntPtr, <MarshalAs(UnmanagedType.I4)>nIndex As WindowLongFlags, ByVal dwNewLong As IntPtr) As IntPtr
  <System.Runtime.InteropServices.DllImport("user32.dll", EntryPoint:="SetWindowLong")> _
  Private Shared Function SetWindowLong32(ByVal hWnd As IntPtr, ByVal nIndex As Integer, ByVal dwNewLong As Integer) As Integer
  End Function

  Public Shared Function SetWindowLongPtr(ByVal hWnd As IntPtr, nIndex As WindowLongFlags, ByVal dwNewLong As IntPtr) As IntPtr
    If IntPtr.Size = 8 Then
      Return SetWindowLongPtr64(hWnd, nIndex, dwNewLong)
    Else
      Return New IntPtr(SetWindowLong32(hWnd, nIndex, dwNewLong.ToInt32))
    End If
  <System.Runtime.InteropServices.DllImport("user32.dll", EntryPoint:="SetWindowLongPtr")> _
  Private Shared Function SetWindowLongPtr64(ByVal hWnd As IntPtr, ByVal nIndex As Integer, ByVal dwNewLong As IntPtr) As IntPtr
  End Function

VB.NET Signature:

Public Declare Function SetWindowLongPtr Lib "user32" Alias "SetWindowLongPtrA" _
        (ByVal hWnd As Long, _
         ByVal nIndex As WindowLongFlags, _
         ByVal dwNewLong As Long) As Long

  Public Shared Function SetWindowLongPtr(ByVal hWnd As IntPtr, ByVal nIndex As Integer, ByVal dwNewLong As IntPtr) As IntPtr
    If IntPtr.Size = 8 Then
      Return SetWindowLongPtr64(hWnd, nIndex, dwNewLong)
    Else
      Return New IntPtr(SetWindowLong32(hWnd, nIndex, dwNewLong.ToInt32))
    End If
  End Function

User-Defined Types:

WindowLongFlags

None.

Alternative Managed API:

Do you know one? Please contribute it!

Notes:

The constants required to call this can be found in the constant section of this site.

Tips & Tricks:

Please add some!

Sample Code:

Please add some!

Error in Windows 7 64 bit under Parallels on Mac, in Visual Studio Express 13 (Visual Basic Forms Application):

When called, the following error was given:

Additional information: Unable to find an entry point named 'SetWindowLongPtrA' in DLL 'user32'

...Geoff Kelly

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