C#调用C++的dll各种传参

1. 如果函数只有传入参数,比如:

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

对应的C#代码为:

[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:

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

对应的C#代码:

[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:

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:

[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,

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:

[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

5. 传出字符数组：

C++定义：

C/C++ Code Copy Code To Clipboard

void __declspec(dllexport) test(int i, double &a, double &b, char t[5])  

C#对应声明：

[DllImport("dll.dll", EntryPoint = "test")]  
public static extern void test(int i, ref double a, ref double b, [Out, MarshalAs(UnmanagedType.LPArray)] char[] t);   
    。。。  
char[] t = new char[5];  
test(i, ref a, ref b, t);  

字符数组的传递基本与4相似，只是mashalAs 时前面加上Out。