修改数据
           SqlConnection con = new SqlConnection(Persist Security Info=False;User ID=sa;Initial Catalog=MYDB;Data Source=DELL-0E2F98ED3C);
            con.Open();
           
            int str=int .Parse( txtID.Text);
         
           string str1 = txtno.Text;
           string str2 = (string)(rdoM.Checked ? "男" : "女");
           string str3 = txtAdress.Text;
            string str4 = "UPDATE Student SET Number=" + str1 + ",  Sex=" + str2 + ", Address=" + str3 + " WHERE stuid=" + str ;
            
            SqlCommand cmmd;
            cmmd = new SqlCommand(str4, con);
            cmmd.ExecuteNonQuery();
            
            con.Close();

char跟varchar应该都一样吧

呵呵