新人求助，怎样将txt导入的数组相加后显示到textbox中

目的是从3个txt文件导入数组，然后按索引相加，结果显示到textbox中，写了代码，是这样的
string strDataFileName3 = strFileName3;
             int SG3 = 0;
             if (strDataFileName3 == "")
             {
                 MessageBox.Show("请选择数据文件！", "提示");
                 //blnCheck = false;
             }
             else if (File.Exists(strDataFileName3))
             {
                 string[] strDataRow = File.ReadAllLines(strDataFileName3, System.Text.Encoding.Default);
                 SG3 = strDataRow.Length;
                 if (SG3 == 0)
                 {
                     MessageBox.Show("数据文件为空！", "提示");
                     //blnCheck = false;
                 }
             }
             else
             {
                 MessageBox.Show("数据文件不存在！", "提示");
                 // blnCheck = false;
             }
                 string[] strDataRow3 = File.ReadAllLines(strDataFileName3, System.Text.Encoding.Default);
                 string[,] c = new string[SG3 - 1, 3];
                 for (int i = 1; i < SG3; i++)
                 {
                     c[i - 1, 0] = strDataRow3[i].Split(',')[0];
                     c[i - 1, 1] = strDataRow3[i].Split(',')[1];
                     c[i - 1, 2] = strDataRow3[i].Split(',')[2];
                 }
            
             string[] strResult = new string[SG1];
             for (int i = 0; i < SG1; i++)
             {
                 strResult[i] = strDataRow1[i] + strDataRow2[i] + strDataRow3[i];
             }
             txtResult.Text = strDataRow3.ToString();            
         }
感觉似乎是读入数组的时候出的错，不过这个本来就不会，求助