转：建一个 Linq 数据库通用的操作类（下）-优快云博客

本文介绍了一个通用的数据访问层(DAL)实现，包括Insert、Update、Delete及Query等基本操作，并通过具体的示例代码展示了如何使用这些通用方法进行数据库操作。

上一篇文章介绍了如何实现一个通用的Insert操作，即直接 Utility.Insert(xxx) 就可以实现了。那么，大家可能就顺理成章的想到是否也可以实现通用的Update， Delete ， Query 操作，答案是肯定的！

下面就让我们来对上一篇提到的DAL扩展一下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

    
namespace DAL
{
    public class Utility
    {
        public static void Insert<T>(T TEntity) where T : class
        {
            var table = TableFactory.CreateTable<T>();
            table.InsertOnSubmit(TEntity);
        }

    
        public static void Delete<T>(T TEntity) where T : class
        {
            var table = TableFactory.CreateTable<T>();
            table.DeleteOnSubmit(TEntity);
        }

    
        public static void Delete<T>(Func<T, bool> predicate) where T : class
        {
            var table = TableFactory.CreateTable<T>();
            var dResult = Where<T>(predicate);
            table.DeleteAllOnSubmit(dResult );
        }

    
        public static void Update<T>(T TEntity, Action<T> action)
        {
            action(TEntity);
            SubmitChanges();
        }

    
        public static void InsertAll<T>(IEnumerable <T> TEntities) where T : class
        {
            var table = TableFactory.CreateTable<T>();
            table.InsertAllOnSubmit( TEntities);
        }

    
        public static void DeleteAll<T>(IEnumerable<T> TEntities) where T : class
        {
            var table = TableFactory.CreateTable<T>();
            table.DeleteAllOnSubmit(TEntities);
        }

    
        public static IEnumerable<T> SelectAll<T>() where T : class
        {
            var table = TableFactory.CreateTable<T>();
            return table.Select(c => c).AsEnumerable();
        }

    
        public static IEnumerable<T> Where<T>(Func<T, bool> predicate) where T : class
        {
            var table = TableFactory.CreateTable<T>();
            return table.Where(predicate).AsEnumerable();
        }

    
        public static void SubmitChanges()
        {
            Database.NWDB.SubmitChanges();
        }
    }
}

同样的，我们也是写一些Test 方法来验证一下是否正确

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using DAL;
using DLinq;
using Toolkits;

    
namespace DALTest
{
    class Program
    {
        static void Main(string[] args)
        {
            //SelectAllTest();  
            InsertTest();
            WhereTest();
            UpdateTest();
            WhereTest();
            DeleteTest1();
            WhereTest();
            Console.WriteLine("All testings are success!");
            Console.Read();
        }

    
        private static void InsertTest()
        {
            Customer _customer=new Customer{ 
                CustomerID="Bruce",
                 ContactName="Lee",
                 CompanyName ="CodingSky",
                 City ="Shenzhen"};
            Utility.Insert(_customer);
            Utility.SubmitChanges();
        }

    
        private static void DeleteTest1()
        {
            Utility.Delete<Customer>(c => c.CustomerID == "Bruce");
            Utility.SubmitChanges();
        }

    
        private static void DeleteTest2()
        {
            var _result= Utility.Where<Customer>(c => c.CustomerID == "Bruce");
            if (_result.Count() > 0)
            {
                Utility.Delete(_result.First());
                Utility.SubmitChanges();
            }
        }

    
        private static void UpdateTest()
        {
            var _result= Utility.Where<Customer>(c => c.CustomerID == "Bruce");
            if (_result.Count() > 0)
            {
                var _customer = _result.First();
                if (_customer != null)
                {
                    Utility.Update(_customer, c =>
                    {
                        c.ContactName = "Jack";
                        c.CompanyName = "Microsoft";
                        c.City = "Beijing";
                    });
                    Utility.SubmitChanges();
                }
            }
        }

    
        private static void SelectAllTest()
        {
            var _result = Utility.SelectAll<Customer>();
            var _list = _result.ToList();
            if (_list.Count == 0)
            {
                Console.WriteLine("No result!");
                return;
            }
            _list.ForEach(c => Console.WriteLine(StringExtension.ToString(c)));
        }

    
        private static void WhereTest()
        {
            var _result= Utility.Where<Customer>(c => c.CustomerID == "Bruce");
            var _list = _result.ToList();
            if (_list.Count == 0)
            {
                Console.WriteLine("No result!");
                return;
     #  