Question

C# 操作MySQL，怎样获取到查询语句中的参数值，题目如下：

MySqlCommand cmd = new MySqlCommand();
cmd.CommandText = "select @systemDatetime = SYSDATE()";

现在的问题是，在只能按照上面这种写法的情况下（可以给cmd对象添加输出参数），我怎样把参数“@systemDatetime”获取到程序中，或者让这个cmd对象能成功的执行（即：调用cmd.ExecuteScalar()方法通过）。反正最终的意思是 怎样通过C# 来执行 “select @systemDatetime = SYSDATE()”这个Sql语句。

Answer 1

using System;
using System.Collections.Generic;
using System.Text;
using System.Data.SqlClient;
using System.Data;
namespace MyBookShop.DAL
{
    public static class DBHelper
    {
        private static SqlConnection connection;
        public static SqlConnection Connection
        {
            get 
            {
             
                string connectionString = "Data Source=Lenovo;Initial Catalog=MyBookShop; uid=sa;Password=9527";
                if (connection == null)
                {
                    connection = new SqlConnection(connectionString);
                    connection.Open();
                }
                else if (connection.State == System.Data.ConnectionState.Closed)
                {
                    connection.Open();
                }
                else if (connection.State == System.Data.ConnectionState.Broken)
                {
                    connection.Close();
                    connection.Open();
                }
                return connection;
            }
        }

        public static int ExecuteCommand(string safeSql)
        {
            SqlCommand cmd = new SqlCommand(safeSql, Connection);
            int result = cmd.ExecuteNonQuery();
            return result;
        }

        public static int ExecuteCommand(string sql, params SqlParameter[] values)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            return cmd.ExecuteNonQuery();
        }

        public static int GetScalar(string safeSql)
        {
            SqlCommand cmd = new SqlCommand(safeSql, Connection);
            int result = Convert.ToInt32(cmd.ExecuteScalar());
            return result;
        }

        public static int GetScalar(params SqlParameter[] values)
        {
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = Connection;
            cmd.CommandText = "Pro_InsertOrder";
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddRange(values);
            int result = Convert.ToInt32(cmd.ExecuteScalar());
            return result;
        }

        public static int GetScalar(string sql, params SqlParameter[] values)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            int result = Convert.ToInt32(cmd.ExecuteScalar());
            return result;
        }

        public static SqlDataReader GetReader(string safeSql)
        {
            SqlCommand cmd = new SqlCommand(safeSql, Connection);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }
        public static SqlDataReader GetReader(string sql, params SqlParameter[] values)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }

        public static DataTable GetDataSet(string safeSql)
        {
            DataSet ds = new DataSet();
            SqlCommand cmd = new SqlCommand(safeSql, Connection);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(ds);
            return ds.Tables[0];
        }

        public static DataTable GetDataSet(string sql, params SqlParameter[] values)
        {
            DataSet ds = new DataSet();
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(ds);
            return ds.Tables[0];
        }
    }
}

追问

在我的实际情况中，这个语句不能包含在存储过程中执行，达不到我要的效果。

追答

你想问的是带参数的存储过程输出？output
http://www.cnblogs.com/qiantuwuliang/archive/2009/06/02/1494627.html