无法通过反射C#接收其他dll中dll的结构数组

我试图通过反射调用另一个dll中的一个函数，该函数返回一个结构数组。但在运行时出现此错误"无法将first_dll.class1.mysturct[，]转换为second_dll.cclass1.mysturt[，]"

第一个dll:

/************  Ist dll ****************/
namespace first_dll
{
    class class1
    {
        public struct mystruct 
        {
            int a;
            byte b;
        };
        public static mystruct[,] function1(mystruct[,] parameter)
        {
            //manupluating structure array here and returning it
            return parameter;   
        }    
    }    
}

第二个dll:

/******** Second dll *********/
namespace second_dll
{
    class class1
    {
        Methodinfo m; // global variable
        public struct mystruct
        {
            int a;    
            byte b;
        };
        public static void load_dll()
        {
            Assembly assembly = Assembly.Load(@"path of first_dll");    
            Type type = assembly.Gettype("first_dll.class1");
            m = type.Getmethod("function1");
        }
        public void function2()
        {
            mystruct[,] structure = new mystruct[10,10];
            //adding value to structure here
            mystruct[,] structure_returning;  // declaring structure to store retuning array;
            //error occur here
            structure_returning = m.Invoke(null,new object[] { structure } )   
        }
    }
}