Search
Module:
Directory

   Desktop Functions:

   Smart Device Functions:


Show Recent Changes
Subscribe (RSS)
Misc. Pages
Comments
FAQ
Helpful Tools
Playground
Suggested Reading
Website TODO List
Download Visual Studio Add-In

SendMessage (user32)
 
.
Summary

C# Signature:

[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, nuint wParam, StringBuilder lParam);

[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, nuint wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);

[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, nuint wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);

[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, nuint wParam, ref nint lParam);

[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, nuint wParam, nint lParam);

VB Signature:

<DllImport("user32.dll", CharSet:=CharSet.Auto)>
Public Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As IntPtr, ByVal lParam As StringBuilder) As IntPtr
End Function

<DllImport("user32.dll", CharSet:=CharSet.Auto)>
Public Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As IntPtr, <MarshalAs(UnmanagedType.LPWStr)> ByVal lParam As String) As IntPtr
End Function

<DllImport("user32.dll", CharSet:=CharSet.Auto)>
Public Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As Integer, <MarshalAs(UnmanagedType.LPWStr)> ByVal lParam As String) As IntPtr
End Function

<DllImport("user32.dll", CharSet:=CharSet.Auto)>
Public Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As Integer, ByRef lParam As IntPtr) As IntPtr
End Function

<DllImport("user32.dll", CharSet:=CharSet.Auto)>
Public Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As Integer, ByVal lParam As IntPtr) As IntPtr
End Function

Notes:

None.

Tips & Tricks:

Used when propagating environment variables, for instance, updating the Path, without requiring a reboot: see also http://support.microsoft.com/kb/104011

Please add some!

Sample Code:

C# Samples

//Set a note to a CommandLink
SendMessage(myCommandLink, BCM_SETNOTE, 0, "My CommandLink Note");

//Retrieve a text using WM_GETTEXT
int length = SendMessage(myHwndHandle, WM_GETTEXTLENGTH, 0, 0).ToInt32();
StringBuilder builder = new StringBuilder(length);
SendMessage(myHwndHandle, WM_GETTEXT, length, builder);

VB.NET Samples

Function GetWindowTitle(hWnd As IntPtr) As String

    Dim length As Integer = SendMessage(hWnd, WM_GETTEXTLENGTH, 0, 0)
    Dim title As New String(New Char, length)
    SendMessage(hWnd, WM_GETTEXT, length+1, title)
    Return title

End Function

Alternative Managed API:

Do you know one? Please contribute it!

Documentation
SendMessage on MSDN

Please edit this page!

Do you have...

  • helpful tips or sample code to share for using this API in managed code?
  • corrections to the existing content?
  • variations of the signature you want to share?
  • additional languages you want to include?

Select "Edit This Page" on the right hand toolbar and edit it! Or add new pages containing supporting types needed for this API (structures, delegates, and more).

 
Access PInvoke.net directly from VS:
Terms of Use
Edit This Page
Find References
Show Printable Version
Revisions