C# Signatures:

[DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam,
   IntPtr lParam);

//Overload for string lParam (e.g. WM_GETTEXT)
[DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam,    
[Out] StringBuilder lParam);

VB Signatures:

Declare Auto Function SendMessage Lib "user32.dll" (ByVal hWnd As IntPtr, _
   ByVal Msg As Integer, ByVal wParam As UIntPtr, _
   ByVal lParam As IntPtr) As IntPtr

<DllImport("User32.dll", CharSet:=CharSet.Auto, Entrypoint:="SendMessage")> _
Private Shared Function SendMessageString(ByVal hwnd As IntPtr, _
   ByVal wMsg As Integer, ByVal wparam As IntPtr, ByVal lparam As String) As IntPtr
End Function

User-Defined Types:

None.

Notes:

1) As the number of messages are varied, just keep overloading the function as you need.

2) Use IntPtr instead of UIntrPtr: The UIntPtr type is not CLS-compliant

Tips & Tricks:

Please add some more!

Sample Code:

//C#
public static String GetWindowText(IntPtr hWnd)
{
     IntPtr txtLength;
     IntPtr retValue;
     IntPtr zeroVal = new IntPtr(0);

     //Get the length of the text
     retValue = SendMessage(hWnd,WM_GETTEXTLENGTH,zeroVal,zeroVal);

     //Setup the size of the sb
     txtLength = retValue;
     StringBuilder sb = new StringBuilder(txtLength.ToInt32() + 1);

     //Get the text of the window/control
     retValue =  SendMessage(hWnd,WM_GETTEXT,txtLength,sb);

     //Return a string
     return sb.ToString();
}

Alternative Managed API:

Do you know one? Please contribute it!

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).