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DllImportAttribute.ExactSpelling Field

Controls whether the DllImportAttribute.CharSet field causes the common language runtime to search an unmanaged DLL for entry-point names other than the one specified.

Namespace:  System.Runtime.InteropServices
Assembly:  mscorlib (in mscorlib.dll)

public bool ExactSpelling

If false, the entry point name appended with the letter A is invoked when the DllImportAttribute.CharSet field is set to CharSet.Ansi, and the entry-point name appended with the letter W is invoked when the DllImportAttribute.CharSet field is set to the CharSet.Unicode. Typically, managed compilers set this field.

The following table shows the relationship between the CharSet and ExactSpelling fields, based on default values imposed by the programming language. You can override the default setting, but do so with caution.

Language

ANSI

Unicode

Auto

Visual Basic

ExactSpelling:=True

ExactSpelling:=True

ExactSpelling:=False

C#

ExactSpelling=false

ExactSpelling=false

ExactSpelling=false

C++

ExactSpelling=false

ExactSpelling=false

ExactSpelling=false

In some cases, Visual Basic developers use the DllImportAttribute, instead of using the Declare statement, to define a DLL function in managed code. Setting the ExactSpelling field is one of those cases.

public class Win32
{
    [DllImport("user32.dll", CharSet=CharSet.Unicode,
        ExactSpelling=true)]
    public static extern int MessageBoxW(IntPtr hWnd, String text,
                                String caption, uint type);
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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