C#调用C++编写的DLL函数, 以及各种类型的参数传递

1. 如果函数只有传入参数,比如:

C/C++ Code  Copy Code To Clipboard

//C++中的输出函数
int __declspec(dllexport) test(const int N)
{
return N+10;
}

对应的C#代码为:

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

private void 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  Copy Code To Clipboard

//C++
void __declspec(dllexport) test(const int N, int& Z)
{
Z=N+10;
}

对应的C#代码:

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[DllImport("test.dll", EntryPoint = "#1")]
public static extern double test(int m, ref int n);

private void 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  Copy Code To Clipboard

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

C#代码:

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[DllImport("test.dll", EntryPoint = "#1")]
public static extern double test(int N, int[] n, ref int Z);

private void button1_Click(object sender, EventArgs e)
{
int N = 0;
int[] n;
n = new int[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,

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

对应的C#代码:

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

private void button1_Click(object sender, EventArgs e)
{
int N = 1000;
int[] n, Z;
n = new int[N];Z = new int[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:http://www.kycis.com/blog/read.php?21