DllImportAttribute Class

Definition

public ref class DllImportAttribute sealed : Attribute

[System.AttributeUsage(System.AttributeTargets.Method, Inherited=false)]
public sealed class DllImportAttribute : Attribute

[System.AttributeUsage(System.AttributeTargets.Method, Inherited=false)]
[System.Runtime.InteropServices.ComVisible(true)]
public sealed class DllImportAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Method, Inherited=false)>]
type DllImportAttribute = class
    inherit Attribute

[<System.AttributeUsage(System.AttributeTargets.Method, Inherited=false)>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type DllImportAttribute = class
    inherit Attribute

Public NotInheritable Class DllImportAttribute
Inherits Attribute

Inheritance

Object

Attribute

DllImportAttribute

Attributes

AttributeUsageAttribute ComVisibleAttribute

Examples

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.

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);
    }
}

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

Remarks

You can apply this attribute to methods.

The DllImportAttribute attribute provides the information needed to call a function exported from an unmanaged DLL. As a minimum requirement, you must supply the name of the DLL containing the entry point.

You apply this attribute directly to C# and C++ method definitions; however, the Visual Basic compiler emits this attribute when you use the Declare statement. For complex method definitions that include BestFitMapping, CallingConvention, ExactSpelling, PreserveSig, SetLastError, or ThrowOnUnmappableChar fields, you apply this attribute directly to Visual Basic method definitions.

Note JScript does not support this attribute. You can use C# or Visual Basic wrapper classes to access unmanaged API methods from JScript programs.

For additional information about using the platform invoke service to access functions in unmanaged DLLs, see Consuming Unmanaged DLL Functions.

Constructors

Fields

Properties

Methods

Explicit Interface Implementations

Applies to

See also

• SetLastError
• ExactSpelling
• PreserveSig
• CallingConvention