三、ADO.Net基础【03】ExecuteScalar

执行查询，并返回查询所返回的结果集中第一行的第一列，忽略其他行列。一般用来简单的获得只有一行一列的查询结果的值。

案例1:

using MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ADO.Net
{
    class Program
    {
        static void Main(string[] args)
        {
            using (MySqlConnection conn = new MySqlConnection("server=127.0.0.1;uid=xiaoping;pwd=825991;database=test;Charset=utf8"))
            using (MySqlCommand cmd = conn.CreateCommand())
            {
                conn.Open();//打开连接
                cmd.CommandText = "select Count(*) from T_Users;";
                int i = Convert.ToInt32(cmd.ExecuteScalar());
                Console.WriteLine(i);
            }
            Console.ReadKey();
        }
    }
}

案例2:

    cmd.CommandText = "Select Password from T_Users where UserName='admin'";
            string pwd = (string)cmd.ExecuteScalar();
            if (string.IsNullOrEmpty(pwd))
            {
                Console.WriteLine("找不到admin");
            }
            else {
                Console.WriteLine("admin的密码：" + pwd);
            }