1. 如果函数只有传入参数,比如:

C/C++ Code

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//C++中的输出函数
int__declspec(dllexport) test(constint N)
{
return N+10;
}

对应的C#代码为:

C# Code

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[DllImport("test.dll", EntryPoint = "#1")]
publicstaticexternint test(int m);

privatevoid button1_Click(object sender, EventArgs e)
{
textBox1.Text= test(10).ToString();
}

2. 如果函数有传出参数,比如:

C/C++ Code

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//C++
void__declspec(dllexport) test(constint N, int& Z)
{
Z=N+10;
}

对应的C#代码:

C# Code

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[DllImport("test.dll", EntryPoint = "#1")]
publicstaticexterndouble test(int m, refint n);

privatevoid button1_Click(object sender, EventArgs e)
{
int N = 0;
test1(10, ref N);
textBox1.Text= N.ToString();
}

3. 带传入数组:

C/C++ Code

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void__declspec(dllexport) test(constint N, constint n[], int& Z)
{
for (int i=0; i<N; i++)
{
Z+=n[i];
}
}

C#代码:

C# Code

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[DllImport("test.dll", EntryPoint = "#1")]
publicstaticexterndouble test(int N, int[] n, refint Z);

privatevoid button1_Click(object sender, EventArgs e)
{
int N = 0;
int[] n;
n = newint[10];
for (int i = 0; i < 10; i++)
{
n[i] = i;
}
test(n.Length, n, ref N);
textBox1.Text= N.ToString();
}

4. 带传出数组:

C++不能直接传出数组,只传出数组指针,

C/C++ Code

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void__declspec(dllexport) test(constint M, constint n[], int *N)
{
for (int i=0; i<M; i++)
{
N[i]=n[i]+10;
}
}

对应的C#代码:

C# Code

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[DllImport("test.dll", EntryPoint = "#1")]
publicstaticexternvoid test(int N, int[] n, [MarshalAs(UnmanagedType.LPArray,SizeParamIndex=1)] int[] Z);

privatevoid button1_Click(object sender, EventArgs e)
{
int N = 1000;
int[] n, Z;
n = newint[N];Z = newint[N];
for (int i = 0; i < N; i++)
{
n[i] = i;
}
test(n.Length, n, Z);
for (int i=0; i<Z.Length; i++)
{
textBox1.AppendText(Z[i].ToString()+"n");
}
}

这里声明函数入口时,注意这句 [MarshalAs(UnmanagedType.LPArray,SizeParamIndex=1)] int[] Z

在C#中数组是直接使用的,而在C++中返回的是数组的指针,这句用来转化这两种不同的类型.

关于MarshalAs的参数用法以及数组的Marshaling,可以参见这篇转帖的文章: