C#--Entity Framework查詢數據（查）

之前操作步驟見《C#-創建Database First Demo》：https://blog.csdn.net/sinat_40003796/article/details/100541514

 

代碼1：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.Entity.Infrastructure;//必須添加的命名空間

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            //簡單查詢
            using (testEntities db = new testEntities())
            {
                // EF本身查詢方法返回的都是IOueryble接口，此時並未查詢數據庫: 只有當調用接口方法獲取數據時，纔會查詢數據庫。
                //DbQuery<student> dbQuery = db.student.Where(u => u.name == "star") as DbQuery<student>;
                DbQuery<student> dbQuery = db.student.Where(u => u.name == "star").OrderBy(u=>u.name).Take(1) as DbQuery<student>;
                //延遲查詢數據庫，真實查詢
                student st =dbQuery.FirstOrDefault();
                Console.WriteLine(st.name + ","+st.age);              
                Console.WriteLine("查詢成功!");           
                Console.ReadLine();
            }
        }
    }
}

運行結果：

 

代碼2：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.Entity.Infrastructure;//必須添加的命名空間

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            //簡單查詢
            using (testEntities db = new testEntities())
            {              
                IQueryable<student> list = db.student;
                foreach (student s in list)
                {
                    Console.WriteLine(s.name + "," + s.age);
                }                 
                Console.WriteLine("查詢成功!");           
                Console.ReadLine();
            }
        }
    }
}

運行結果：