我正在尝试从C#调用以下简单的C函数:
SIMPLEDLL_API const char* ReturnString()
{
return "Returning a static string!";
}
使用下面的P/Invoke声明(有没有return属性,都没有区别):
[DllImport("SimpleDll")]
[return: MarshalAs(UnmanagedType.LPStr)]
public static extern string ReturnString();
如果DLL是调试版本,但在发布版本(AccessViolationException)中崩溃,则此方法有效。
我调用了十几个其他简单的函数,这是唯一失败的函数(下面是其他函数:)
[DllImport("SimpleDll")] public static extern int NextInt();
[DllImport("SimpleDll")] public static extern void SetNextInt(int x);
[DllImport("SimpleDll")] public static extern int AddInts(int a, int b);
[DllImport("SimpleDll")] public static extern int AddFourInts(int a, int b, int c, int d);
[DllImport("SimpleDll")] public static extern double AddDoubles(double x, double y);
[DllImport("SimpleDll")] public static extern IntPtr AddDoublesIndirect(ref double x, ref double y);
[DllImport("SimpleDll")] [return: MarshalAs(UnmanagedType.U1)]
public static extern char CharStringArgument([MarshalAs(UnmanagedType.LPStr)]string s);
[DllImport("SimpleDll")] [return: MarshalAs(UnmanagedType.U2)]
public static extern char WCharStringArgument([MarshalAs(UnmanagedType.LPWStr)]string s);
[DllImport("SimpleDll")] [return: MarshalAs(UnmanagedType.LPWStr)]
public static extern string ReturnWString();
[DllImport("SimpleDll")] [return: MarshalAs(UnmanagedType.BStr)]
public static extern string ReturnBSTR();
[DllImport("SimpleDll")] public static extern System.Drawing.Point MakePoint(int x, int y);
[DllImport("SimpleDll")] public static extern IntPtr MakePointIndirect(int x, int y);
[DllImport("SimpleDll")] public static extern int GetPointY(System.Drawing.Point p);
[DllImport("SimpleDll")] public static extern int GetPointYIndirect(ref System.Drawing.Point pp);
[DllImport("SimpleDll")] public static extern int SumIntegers(ref int firstElem, int size);
发布于 2011-06-10 06:46:24
或者可以试着用
[DllImport("SimpleDll")]
public static extern IntPtr ReturnString();
在您的调用代码中,使用Marshal类
string ret = System.Runtime.InteropServices.Marshal.PtrToStringAnsi(PInvoke.ReturnString());
发布于 2016-07-31 03:16:09
也可以使用自定义封送拆收器来完成此操作:
class ConstCharPtrMarshaler : ICustomMarshaler
{
public object MarshalNativeToManaged(IntPtr pNativeData)
{
return Marshal.PtrToStringAnsi(pNativeData);
}
public IntPtr MarshalManagedToNative(object ManagedObj)
{
return IntPtr.Zero;
}
public void CleanUpNativeData(IntPtr pNativeData)
{
}
public void CleanUpManagedData(object ManagedObj)
{
}
public int GetNativeDataSize()
{
return IntPtr.Size;
}
static readonly ConstCharPtrMarshaler instance = new ConstCharPtrMarshaler();
public static ICustomMarshaler GetInstance(string cookie)
{
return instance;
}
}
并像这样使用它:
[DllImport("SimpleDll")]
[return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(ConstCharPtrMarshaler))]
public static extern string ReturnString();
发布于 2011-06-10 06:46:58
处于发布模式的C++编译器将常量放入受保护的数据页中;试图将其传递给C#会导致问题。在调试模式下,编译器不会优化数据页中的常量,因此不存在保护问题。
https://stackoverflow.com/questions/6300093
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