C#与C互操作

C#给C++传递char**（转载）

extern "C" _declspec(dllexport)void GetResult(char* a,char** pBuf)
{
sprintf((pBuf[0]),"vc11111111");
sprintf((pBuf[1]),"vc222222222222222");

}

C#部分写法：

//
[DllImport("CPPCharXingXing.dll", EntryPoint = "GetResult", CallingConvention = CallingConvention.Cdecl)]
public static extern void GetResultCharXingXing(string a, IntPtr[] refSb);
static void Main(string[] args)
{

//StringBuilder sb = new StringBuilder();
//bool b=GetResultCharXing(0,sb);
//string str = sb.ToString();
//b= GetResultCharXing(1, sb);
//str = sb.ToString();

StringBuilder refSb = new StringBuilder();
string a = "TomCat";
string b = "aa"; //不能为空字符串
string c = "cc"; //不能为空字符串
IntPtr[] pts = new IntPtr[2];
pts[1] = Marshal.StringToHGlobalAnsi(c);
pts[0] = Marshal.StringToHGlobalAnsi(b);
GetResultCharXingXing(a,pts);
string s = Marshal.PtrToStringAnsi(pts[0]);
string ss = Marshal.PtrToStringAnsi(pts[1]);
//MessageBox.Show($"S为{s}----ss为{ss}");
Marshal.FreeHGlobal(pts[0]);
Marshal.FreeHGlobal(pts[1]);
}

C#给C传递char * 型

c传递const char * ，对于c# 就是byte *，因为c中char只占1位；
而 char 就是byte
const char * 也可以是string ，但是char *必须是 byte*，但最好变为byte* 型
因此，传入的buff全部为byte*型

C# 调用c可变参数的库函数sprintf，必须要注意的是：类型必须严格对应上，例如：format中，含有"%d"，对应参数必须为int型

[DllImport("msvcrt.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
        static unsafe extern int sprintf(byte* buff, byte* format, byte* arg1, byte* arg2);

        [DllImport("msvcrt.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
        static unsafe extern int sprintf(byte* buff, string format, string arg0, int arg1, byte* arg2, double arg3, double arg4, double arg5);

        [DllImport("msvcrt.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
        static unsafe extern int sprintf(byte* buff, string format, string arg0, byte* arg1);

public static int Csprintf(char[] str, string format, string arg1, string arg2)
        {
            unsafe
            {
                byte* strr = stackalloc byte[str.Length];
                for (int j = 0; j < str.Length; j++)
                {
                    strr[j] = (byte)str[j];
                }
                //
                byte* formatt = stackalloc byte[format.Length + 1];
                for (int j = 0; j < format.Length; j++)
                {
                    formatt[j] = (byte)format[j];
                }
                formatt[format.Length] = (byte)'\0';
                //
                byte* arg11 = stackalloc byte[arg1.Length + 1];
                for (int j = 0; j < arg1.Length; j++)
                {
                    arg11[j] = (byte)arg1[j];
                }
                arg11[arg1.Length] = (byte)'\0';
                //
                byte* arg22 = stackalloc byte[arg2.Length + 1];
                for (int j = 0; j < arg2.Length; j++)
                {
                    arg22[j] = (byte)arg2[j];
                }
                arg22[arg2.Length] = (byte)'\0';//记得要添加字符串结束标志
                //
                int t = sprintf(strr, formatt, arg11, arg22);
                //
                for (int j = 0; j < str.Length; j++)
                {
                    str[j] = (char)strr[j];
                }
                return t;
            }
        }

 public static int sprintf(byte[] buffer, string format, string arg0, char[] arg1)
        {
            unsafe
            {
                byte* strr = stackalloc byte[buffer.Length];
                //
                byte* arg01 = stackalloc byte[arg1.Length + 1];
                for (int j = 0; j < arg1.Length; j++)
                {
                    arg01[j] = (byte)arg1[j];
                }
                arg01[arg1.Length] = (byte)'\0';
                //
                int t = sprintf(strr, format, arg0, arg01);
                //
                for (int j = 0; j < buffer.Length; j++)
                {
                    buffer[j] = strr[j];
                }
                return t;
            }
        }