C#返回mysql的行数

Question

如果在 php 中我们可以做一些类似 where $result is some query 的事情:

$result = mysql_query("SELECT * FROM student");
if (mysql_num_rows($results) !==0)
{
//do operation.
}  
else 
echo "no data found in databasae";  

如果我想在 C# 语言中执行此操作，这相当于什么？请指教。

Answer 1

我已经使用 mysql 创建了一个完整的控制台应用程序。在您的选择查询中，您正在查询整个表，这是一个坏主意。使用 limit 只获得一个结果 - 这应该足以确定表中是否有任何行。

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


namespace ConsoleApplication29
{
    class Program
    {
        static void Main(string[] args)
        {
            if (AnyRows())
            {
                Console.WriteLine("There are rows in the database");
            }
            else
                Console.WriteLine("no data found in database");

            //This will pause the output so you can view the results. Otherwise you will see the dos screen open then close.
            Console.Read();
        }

        //This is the Methos to call
        public static bool AnyRows()
        {
            string connectionString = "Server=localhost;Database=test;Uid=root;Pwd=yourpassword;";

            //Wrap this is using clause so you don't have to call connection close
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                connection.Open();
                string query  = "select * from mytable limit 1";

                using (MySqlCommand command = new MySqlCommand(query, connection))
                {
                    MySqlDataReader reader = command.ExecuteReader();
                    return reader.HasRows;
                }
            }
        }
    }
}