Use this field with a member of the CharSet enumeration to specify the marshaling behavior of string parameters and to specify which entry-point name to invoke (the exact name given or a name ending with "A" or "W"). The default enumeration member for C# and Visual Basic is CharSet.Ansi and the default enumeration member for C++ is CharSet.None, which is equivalent to CharSet.Ansi. In Visual Basic, you use the Declare statement to specify the CharSet field.

The ExactSpelling field influences the behavior of the CharSet field in determining which entry-point name to invoke. For a detailed description and examples of the string marshaling and name matching behavior associated with the CharSet field, see Specifying a Character Set.

The following code example shows how to use the DllImportAttribute attribute to import the Win32 MessageBox function. The code example then calls the imported method.

Imports System
Imports System.Runtime.InteropServices

Module Example

    ' Use DllImport to import the Win32 MessageBox function.
    <DllImport("user32.dll", CharSet:=CharSet.Unicode)> _
    Function MessageBox(ByVal hwnd As IntPtr, ByVal t As String, ByVal caption As String, ByVal t2 As UInt32) As Integer
    End Function


    Sub Main()
        ' Call the MessageBox function using platform invoke.
        MessageBox(New IntPtr(0), "Hello World!", "Hello Dialog", 0)
    End Sub

End Module

using System;
using System.Runtime.InteropServices;

class Example
{
    // Use DllImport to import the Win32 MessageBox function.
    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
    public static extern int MessageBox(IntPtr hWnd, String text, String caption, uint type);

    static void Main()
    {
        // Call the MessageBox function using platform invoke.
        MessageBox(new IntPtr(0), "Hello World!", "Hello Dialog", 0);
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

.NET Framework

.NET Compact Framework

XNA Framework

Reference