如何使用 <DllImport> 在VB.NET中？

Question

我应该如何DLLImport在VB.NET中的东西？ 一个例子是：

<DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
Private Shared Function GetWindowText(ByVal hwnd As IntPtr, ByVal lpString As StringBuilder, ByVal cch As Integer) As Integer

End Function

如果我把它放在一个类或其他地方，我得到“DLLimport未定义”我使用的是Visual Studio 2008 Professional

Answer 1

您必须将Imports System.Runtime.InteropServices添加到源文件的顶部。

或者，您可以完全限定属性名称：

<System.Runtime.InteropService.DllImport("user32.dll", _
    SetLastError:=True, CharSet:=CharSet.Auto)> _

Answer 2

Imports System.Runtime.InteropServices

Answer 3

我在pinvoke.net上的getwindowtext（user32）中看到你可以放置一个MarshalAs语句来声明StringBuffer等同于LPSTR。

<DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Ansi)> _
Public Function GetWindowText(hwnd As IntPtr, <MarshalAs(UnManagedType.LPStr)>lpString As System.Text.StringBuilder, cch As Integer) As Integer
End Function

Answer 4

你也可以试试这个

Private Declare Function GetWindowText Lib "user32.dll" (ByVal hwnd As IntPtr, ByVal lpString As StringBuilder, ByVal cch As Integer) As Integer

我总是使用Declare Function而不是DllImport ...它更简单，它更短，也一样

Answer 5

我知道这已经得到了解答，但是这里有一个例子给那些试图在vb项目中使用SQL Server Types的人：

            Imports System
            Imports System.IO
            Imports System.Runtime.InteropServices

            Namespace SqlServerTypes
                Public Class Utilities



                    <DllImport("kernel32.dll", CharSet:=CharSet.Auto, SetLastError:=True)>
                    Public Shared Function LoadLibrary(ByVal libname As String) As IntPtr

                    End Function

                    Public Shared Sub LoadNativeAssemblies(ByVal rootApplicationPath As String)
                        Dim nativeBinaryPath = If(IntPtr.Size > 4, Path.Combine(rootApplicationPath, "SqlServerTypes\x64\"), Path.Combine(rootApplicationPath, "SqlServerTypes\x86\"))
                        LoadNativeAssembly(nativeBinaryPath, "msvcr120.dll")
                        LoadNativeAssembly(nativeBinaryPath, "SqlServerSpatial140.dll")
                    End Sub

                    Private Shared Sub LoadNativeAssembly(ByVal nativeBinaryPath As String, ByVal assemblyName As String)
                        Dim path = System.IO.Path.Combine(nativeBinaryPath, assemblyName)
                        Dim ptr = LoadLibrary(path)

                        If ptr = IntPtr.Zero Then
                            Throw New Exception(String.Format("Error loading {0} (ErrorCode: {1})", assemblyName, Marshal.GetLastWin32Error()))
                        End If
                    End Sub
                End Class
            End Namespace