c# 二维数组排序，代码如下

decimal sum = 0;
Console.WriteLine("编号"+"\t"+"姓名" +"\t"+"语文" + "\t" + "数学" + "\t" + "英语" +"\t"+ "平均分");
for (int i = 0; i < 10; i++)
{
for (int j = 2; j < 5; j++)
{
sum += decimal.Parse(StudentScore[i, j]);
}
StudentScore[i, 5] = (sum / 3).ToString();//计算每行数据的平均值
for (int j = i + 1; j < 10; j++)
{
if (decimal.Parse(StudentScore[i, 5]) <decimal.Parse(StudentScore[j, 5]))
{
for (int t = 0; t < 6; t++)
{
temp[t] = StudentScore[i, t];//temp[5]一位数组用于选择法转换
StudentScore[i, t] = StudentScore[j, t];
StudentScore[j, t] = temp[t];
}

}

}
}
为什么运行结果平均值不对
string[,] StudentScore = new string[10, 6] { { "", "", "", "", "","" }, { "","", "", "", "", "" } ,
{"","","","","",""},{"","","","","",""},{"","","","","",""},{"","","","","",""},{"","","","","",""},
{"","","","","",""},{"","","","","",""},{"","","","","",""}};
string[] temp = new string[6];//用于行记录之间数据的转换；

＃定义M 10U
＃定义20U
＃包括中

INT主要（无效）{

//第一位的，你可以直接[] []的访问。但记忆是不连续的，不是很推荐，除非对M \ n不知道
INT ** PNUM; //为int例如
PNUM =新的诠释* [J];
为（int i = 0;我<米;我+ +）
{
PNUM [I] =新的int [N];
}删除时

//是
为（int J = 0;<M，J + +）
{
删除[] PNUM [I];
}
删除[] PNUM;

//第二个e799bee5baa6e4b893e5b19e31333335336461连续的内存，而不是[] []，最值得推荐的。没有[] []，但你可以计算啊
//这是一维数组转换成一个二维数组
诠释* 1 =新的int [M * 22 N]至[I * N + J ];
// A [I * N + j]为A [I] [J]
删除[] A;

//第三
//内存是不连续的，可以[] []，是一种特殊情况，在比较大的第一种情况的限制，比第一个好消息，可直接删除，方便
// n如果真的知道多少，你可以这样做的时候（在这种情况下，内存连续）利用这一点，例如，二维数组参数，不是很推荐 - INT（* pNum3） [N] =新的int [M] [N];
删除]压力;有限公司返回0;
}