C# 二维数组填充datagridview慢是什么原因？

Question

C# WinForm程序，用Sqldatareader遍历表，然后放到二维数组里，在填到datatable里，datagridview.datasource=datatable，大体就这思路，显示的没问题，就是速度奇慢，得2分多钟...谁知道问题出在哪里啊？用listview显示也是很慢，2分多钟

18行，48列的数据，还不到1000条
代码如下：
conn = new SqlConnection(connstr);
conn.Open(); //打开数据库连接

          string sql1 = "select medname,medpos from storetable where medpos like '01%' ";
       
       Command cmd1 = new SqlCommand(sql1, conn);
        
        dr1 = cmd1.ExecuteReader();

        string [,] data=new string[50,50]; //二维数组data

        if (dr1.HasRows)
        {
            while (dr1.Read())
            {
                string name = dr1[0].ToString();  //dr1[0]读取的是汉字
                string pos = dr1[1].ToString();    //dr1[1]读取的是数字
                int rownum = int.Parse(pos.Substring(2, 2));
                int colnum = int.Parse(pos.Substring(4, 2));

                data[rownum, colnum] = name;   //把数字对应的汉字放入二维数组，最终显示的时候只显示汉字
               

                DataTable dt = new DataTable(); //创建表

                //新增列
                for (int a = 0; a < 48; a++)
                
                    dt.Columns.Add(data[0, a], typeof(string));

                for (int b = 0; b < 18; b++)
                {
                    DataRow row = dt.NewRow();

                    for (int c = 0; c < 48; c++)
                    {
                        row[c] = data[b + 1, c + 1];
                    }

                    dt.Rows.Add(row);

                }
                    this.dataGridView1.DataSource = dt;

            }
        }
            

       

Answer 1

            string sql1 = "select medname,medpos from storetable where medpos like '01%' ";

            Command cmd1 = new SqlCommand(sql1, conn);

            dr1 = cmd1.ExecuteReader();

            string[,] data = new string[50, 50]; //二维数组data
            DataTable dt = new DataTable(); //创建表
            this.dataGridView1.DataSource = dt;
            if (dr1.HasRows)
            {
                while (dr1.Read())
                {
                    string name = dr1[0].ToString();  //dr1[0]读取的是汉字
                    string pos = dr1[1].ToString();    //dr1[1]读取的是数字
                    int rownum = int.Parse(pos.Substring(2, 2));
                    int colnum = int.Parse(pos.Substring(4, 2));

                    data[rownum, colnum] = name;   //把数字对应的汉字放入二维数组，最终显示的时候只显示汉字
                }
                //新增列
                for (int a = 0; a < 48; a++)

                    dt.Columns.Add(data[0, a], typeof(string));
                for (int b = 0; b < 18; b++)
                {
                    DataRow row = dt.NewRow();

                    for (int c = 0; c < 48; c++)
                    {
                        row[c] = data[b + 1, c + 1];
                    }

                    dt.Rows.Add(row);

                }
                
            }