主攻ASP.NET.3.5.MVC架构之重生: LINQ(六)

LINQ to SQL

LINQ to SQL执行标准数据库命令

*查询并创建Id&Title匿名类型

LINQ to SQL Code

MydataDataContext data = new MydataDataContext();

            var query = data.Article.Select(m => new { Id = m.ArticleID, Title = m.ArticleTitle });

SqlCode

SELECT [t0].[ArticleID] AS [Id], [t0].[ArticleTitle] AS [Title]

FROM [dbo].[Article] AS [t0]

 

 

*查询特殊数据行数

Where()方法之前调用Select()方法,先使用Where()过滤数据

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            var query = data.Article

                .Where(m=>m.CategoryID==30&&m.ArticleID>20)

                .Select(m => new { Id = m.ArticleID,Cid=m.CategoryID, Title = m.ArticleTitle });

SqlCode

SELECT [t0].[ArticleID] AS [Id], [t0].[CategoryID] AS [Cid], [t0].[ArticleTitle] AS [Title]

FROM [dbo].[Article] AS [t0]

WHERE ([t0].[CategoryID] = 30) AND ([t0].[ArticleID] > 20)

 

*查询特殊数据行数

Where()方法之前调用Select()方法,先使用Where()过滤数据

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            var query = data.Article

                .Where(m=>m.CategoryID==30&&m.ArticleID>20)

                .Select(m => new { Id = m.ArticleID,Cid=m.CategoryID, Title = m.ArticleTitle });

SqlCode

SELECT [t0].[ArticleID] AS [Id], [t0].[CategoryID] AS [Cid], [t0].[ArticleTitle] AS [Title]

FROM [dbo].[Article] AS [t0]

WHERE ([t0].[CategoryID] = 30) AND ([t0].[ArticleID] > 20)

 

 

*查询按创建发布时间排序，并按照[Sort]字段排序

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            var query = data.Article.OrderBy(m => m.CreateTime).ThenBy(m => m.Sort);

SqlCode

SELECT [t0].[ArticleID], [t0].[CategoryID], [t0].[ArticleTitle], [t0].[ArticleBody], [t0].[IsTop], [t0].[Sort], [t0].[CreateTime], [t0].[SysUserID], [t0].[State]

FROM [dbo].[Article] AS [t0]

ORDER BY [t0].[CreateTime], [t0].[Sort]

 

*查询按创建发布时间倒序，并按照[IsTop]字段排序

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            var query = data.Article.OrderBy(m => m.IsTop).ThenByDescending(m => m.CreateTime); SqlCode

SELECT [t0].[ArticleID], [t0].[CategoryID], [t0].[ArticleTitle], [t0].[ArticleBody], [t0].[IsTop], [t0].[Sort], [t0].[CreateTime], [t0].[SysUserID], [t0].[State]

FROM [dbo].[Article] AS [t0]

ORDER BY [t0].[IsTop], [t0].[CreateTime] DESC

 

*查询单独一行

LINQ to SQL Code

           var query = data.Article.Single(m => m.ArticleID == 54);

返回单独一行实例

 

 

 

 

 

 

 

 

 

 

 

 

*查询返回字母a开头的数据。（LINK Select）

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            var query = data.Article.Where(m => m.ArticleTitle.StartsWith("a"));

using System.Data.Linq.SqlClient;

            MydataDataContext data = new MydataDataContext();

            var query = data.Article.Where(m => SqlMethods.Like(m.ArticleTitle,"a%"));

SqlCode

SELECT [t0].[ArticleID], [t0].[CategoryID], [t0].[ArticleTitle], [t0].[ArticleBody], [t0].[IsTop], [t0].[Sort], [t0].[CreateTime], [t0].[SysUserID], [t0].[State]

FROM [dbo].[Article] AS [t0]

WHERE [t0].[ArticleTitle] LIKE 'a%'

 

 

*连接不同表，内连接（INNER JOIN）

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            var query = data.AD

                        .Join(data.AdClass,c=>c.ClassID,m=>m.ClassID,(c,m)=>new {c.ID,c.ClassID,m.ClassName});

SqlCode

SELECT [t0].[ID], [t0].[ClassID], [t1].[ClassName]

FROM [dbo].[AD] AS [t0]

INNER JOIN [dbo].[AdClass] AS [t1] ON [t0].[ClassID] = ([t1].[ClassID])

 

 

 

*连接不同表，外连接（OUTER JOIN）

LINQ to SQL Code

            var query = from c in data.AD

                        join m in data.AdClass

                        on c.ClassID equals m.ClassID into cm

                        from m in cm.DefaultIfEmpty()

                        select new { c.ID, c.ClassID, m.ClassName };

SqlCode

 

SELECT [t0].[ID], [t0].[ClassID], [t1].[ClassName] AS [ClassName]

FROM [dbo].[AD] AS [t0]

LEFT OUTER JOIN [dbo].[AdClass] AS [t1] ON [t0].[ClassID] = ([t1].[ClassID])

 

 

 

*LINQ tp SQL 插入数据（Insert Data）

1.使用InsertOnSubmit()方法将实体Add到存在表中

2.调用DataContext中SubmitChanges()

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            SysUser su = new SysUser();

            su.Logname = "testLoginName";

            su.Password = "123456";

            su.State = 1;

            su.CreateTime = DateTime.Now;

            data.SysUser.InsertOnSubmit(su);

            data.SubmitChanges();

            int userid = su.SysUserID;

 

*LINQ tp SQL 更新修改数据(UpDate Data)

1.修改实体属性

2.调用DataContext中SubmitChanges()

3.对实体和底层数据更新修改

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            SysUser su = data.SysUser.Single(m => m.SysUserID == 13);

            su.Logname = "updateUserName";

            su.Password = "654321";

            data.SubmitChanges();

 

 

 

 

 

 

 

*LINQ tp SQL 删除数据(Delete Data)

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            SysUser suDelete = data.SysUser.Single(m => m.SysUserID == 13);

            data.SysUser.DeleteOnSubmit(suDelete);

            data.SubmitChanges();

 

 

*动态查询

执行动态SQL语句

LINQ to SQL Code

            MydataDataContext data = new MydataDataContext();

            //data.ExecuteCommand("INSERT INTO [SysUser]([Logname],[Password],[State],[CreateTime])VALUES(@p0,@p1)");

            var query=data.ExecuteQuery(typeof(SysUser),"Select * from sysuser WHERE sysuserid=@p0",new object[]{2});

 

 

*LINQ to SQL 查询日志

1<%@ Page Trace="true"%> => Trace="true"

2调用方法//context.Log = new TraceWrite();

TraceWrite.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Text;

using System.IO;

using System.Globalization;

namespace AllFor.Helpers

{

    public class TraceWrite:TextWriter

    {

        public override void Write(string value)

        {

            HttpContext.Current.Trace.Warn(value);

        }

        public override void Write(char[] buffer,int index,int count)

        {

            HttpContext.Current.Trace.Warn("LINQ",new string(buffer,index,count));

        }

        public override Encoding Encoding

        {

            get { return Encoding.Unicode; }

        }

        public TraceWrite():base(CultureInfo.CurrentCulture)

        {

        }

    }

}