在C＃中使用DLL＃

Question

我正尝试在C＃windows窗体应用程序中使用旧的C DLL。看起来像我使用错误的数据类型的输出参数。

DLL源代码：

#ifdef __cplusplus 
#define EXPORT extern "C" __declspec (dllexport) 
#else 
#define EXPORT __declspec (dllexport) 
#endif 

EXPORT INT CALLBACK Complemento (LPSTR) ; 
EXPORT INT CALLBACK MatchCode (LPSTR, LPSTR, LPSTR, LPSTR); 

C＃DLL导出

[DllImport(
    @"<MYDIR>Fonetica.dll", 
    CharSet = CharSet.Ansi)] 
public static extern int MatchCode(
    String n, 
    String s, 
    String e, 
    [MarshalAs(UnmanagedType.LPStr)] out String retorno); 

C＃DLL使用码

String match = String.Empty; 

MatchCode(pefi.Nome, String.Empty, String.Empty, out match); 

树第一参数被输入，最后一个是输出。

I'm收到此异常：

System.AccessViolationException was unhandled 
    Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt. 
    Source=mscorlib 
    StackTrace: 
     at System.String..ctor(SByte* value) 
     at System.StubHelpers.CSTRMarshaler.ConvertToManaged(IntPtr cstr) 
     at WFMatchCode.Form1.MatchCode(String n, String s, String e, String& retorno) 
     at WFMatchCode.Form1.button1_Click(Object sender, EventArgs e) in C:\Users\computecnica.alexand\Documents\Visual Studio 2010\Projects\WFMatchCode\WFMatchCode\Form1.cs:line 91 
     at System.Windows.Forms.Control.OnClick(EventArgs e) 
     at System.Windows.Forms.Button.OnClick(EventArgs e) 
     at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent) 
     at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks) 
     at System.Windows.Forms.Control.WndProc(Message& m) 
     at System.Windows.Forms.ButtonBase.WndProc(Message& m) 
     at System.Windows.Forms.Button.WndProc(Message& m) 
     at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) 
     at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) 
     at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) 
     at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg) 
     at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData) 
     at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) 
     at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) 
     at System.Windows.Forms.Application.Run(Form mainForm) 
     at WFMatchCode.Program.Main() in c:\users\computecnica.alexand\documents\visual studio 2010\Projects\WFMatchCode\WFMatchCode\Program.cs:line 18 
     at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) 
     at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) 
     at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() 
     at System.Threading.ThreadHelper.ThreadStart_Context(Object state) 
     at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) 
     at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) 
     at System.Threading.ThreadHelper.ThreadStart() 
    InnerException: 

Answer 1

[DllImport(@"Fonetica.dll", CharSet = CharSet.Ansi)] 
public static extern int MatchCode(String n, String s, String e, StringBuilder retorno); 

然后，您必须通过有足够的能力采取一切变得写入的一个StringBuilder。同样的方式，你必须通过一个足够大的数组C：

var capacity = 1000; // change this to whatever you need 
var buffer = new StringBuilder(capacity); 

var result = MatchCode("test", "test", "test", buffer); 

var output = buffer.ToString();