查询数据的问题。 我哪里写错了？？

[lijing3333]

 public static int insertDataQu(string cmdString)
        {
            string connString = "server=.\\SQLEXPRESS;database=stumanage;uid=sa;pwd=sa";          
            using (SqlConnection conn = new SqlConnection(connString))
            {
                using (SqlCommand cmd = new SqlCommand(cmdString, conn))
                {
                  conn.Open();
                  int count = cmd.ExecuteNonQuery();
                  return count;
                }
            }
        }

      private void insertBut_Click(object sender, EventArgs e)
        {
            string myclass=cName.Text;
            string myteacher=cTea.Text;
            string cmdString = "select count(c_class) from classinfo where c_class='" + myclass + "'";
            int aa =DB.insertDataQu(cmdString);
            MessageBox.Show(aa.ToString());
         
        }

我检索表 chlassinfo 里面的字段 c_class 为什么返回的数字是-1? 我存在这个数据的啊。 不是应该返回1么？
什么原因？ 哪里错了？？

[tuoshi]

不应用ExecuteNonQuery，应该用ExecuteReader。

[fallenjh]

private void insertBut_Click(object sender, EventArgs e)
{
string myclass=cName.Text;
string myteacher=cTea.Text;
string cmdString = "select count(c_class) from classinfo where c_class='" + myclass + "'";
//MessageBox.Show(cmdString);看看组织的语句对不对先
int aa =DB.insertDataQu(cmdString);
MessageBox.Show(aa.ToString());

}

[SQL77]

 object count =cmd1.ExecuteScalar();

[SQL77]

private void insertBut_Click(object sender, EventArgs e)
        {
            string myclass=cName.Text;
            string myteacher=cTea.Text;
            string cmdString = "select count(c_class) from classinfo where c_class='" + myclass + "'";
            object count =cmd.ExecuteScalar();
            MessageBox.Show(aa.ToString());
         
        }

???

[tuoshi]

 public static int insertDataQu(string cmdString)
        {
            string connString = "server=.\\SQLEXPRESS;database=stumanage;uid=sa;pwd=sa";          
            using (SqlConnection conn = new SqlConnection(connString))
            {
                using (SqlCommand cmd = new SqlCommand(cmdString, conn))
                {
                  conn.Open();
                  SqlClient.SqlDataReader sqlDataReader = sqlCommand.ExecuteReader;
                  sqlDataReader.Read();
                  int count = sqlDataReader.GetInt32(0);
                  return count;
                }
            }
        }

[lk829]

ExecuteNonQuery()只能用于update delete insert返回影响的行数