在C#中,如何调用返回包含字符串指针的非托管结构的DLL函数？

typedef struct {
    char* str;
    int len;
} MyStruct;

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct MyStruct
{
    [MarshalAs(UnmanagedType.LPStr)]
    public string str;
    public int len;
}

__declspec(dllexport) MyStruct* GetMyStruct();

[DllImport("YourDllName.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
public static extern IntPtr GetMyStruct();

IntPtr ptr = GetMyStruct();
MyStruct myStruct = (MyStruct)Marshal.PtrToStructure(ptr, typeof(MyStruct));