LinQ技术--转

对‘Microsof SQL Server’数据源的‘用于 SQL server 的.NET Framework 数据提供程序’支持。
对‘Microsof SQL Server’数据源的‘用于 OLE DB 的.NET Framework 数据提供程序’不支持。
对‘Microsoft ODBC 数据源‘用于 用于 ODBC 的 .NET Framework 数据提供程序’不支持。
对‘Microsoft Access 数据库文件’数据源的‘用于OLE DB的.NET Framework 数据提供程序’不支持。
即，对SQL Server的专用数据提供程序支持，对OLE DB、ODBC数据提供程序不支持，对Oralce专用属于提供程序未做测试

建议：

因 为Linq to sql 的数据持久方式不能跨数据库平台，因此后台如果是sql server 数据库，可以使用此orm，调用过程最好是‘业务逻辑层’===》‘数据访问层’====》‘此Linq to sql 的orm对象’，这样，如果要跨数据库，则需要重写‘数据访问层’（此数据访问层相当于一个代理），对上面的各层不会产生影响。

 protected void Page_Load(object sender, EventArgs e)
    {
        DataPersonDataContext dc = new DataPersonDataContext();
        //查询2
        GridView1.DataSource = from p in dc.Person
                               where p.ID < 100 && p.Name.StartsWith("bei")
                               select new { 编码 = p.ID, 姓名 = p.Name, 电话 = p.Tel };
        //查询3
        var varPerson = from p in dc.Person
                         where p.ID < 100 && p.Tel.StartsWith("010")
                         orderby p.Name descending
                         select new { 编码 = p.ID, 姓名 = p.Name, 电话 = p.Tel };
        GridView1.DataSource = varPerson;
        //添加
        Person person1 = new Person();
        person1.Name = "xianggang";
        person1.Tel = "00852-11111111";
        dc.Person.InsertOnSubmit(person1);
        dc.SubmitChanges();
        //更新
        Person person2 = dc.Person.Where(p => p.Name == "xianggang").First();
        person2.Tel = "00852-11111110";
        dc.SubmitChanges();

        //删除
        Person person3 = dc.Person.Where(p => p.Name == "xianggang").First();
        dc.Person.DeleteOnSubmit(person3);
        dc.SubmitChanges();
        //查询1
        GridView1.DataSource = dc.Person;
        GridView1.DataBind();
    }
=>
     返回结果：
ID    Name    Tel
1    beijing    010-0000000
2    shanghai    021-0000000
13    xianggang    00852-11111111
14    xianggang    00852-11111111
15    xianggang    00852-11111111
16    xianggang    00852-11111111
=>
=>
1、创建linq to sql（即DataPerson.dbml文件）：
#pragma warning disable 1591
//------------------------------------------------------------------------------
// <auto-generated>
//     此代码由工具生成。
//     运行库版本:2.0.50727.1433
//
//     对此文件的更改可能会导致不正确的行为，并且如果
//     重新生成代码，这些更改将会丢失。
// </auto-generated>
//------------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.Linq;
using System.Data.Linq.Mapping;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
[System.Data.Linq.Mapping.DatabaseAttribute(Name="msdb")]
public partial class DataPersonDataContext : System.Data.Linq.DataContext
{

private static System.Data.Linq.Mapping.MappingSource mappingSource = new AttributeMappingSource();

#region Extensibility Method Definitions
partial void OnCreated();
partial void InsertPerson(Person instance);
partial void UpdatePerson(Person instance);
partial void DeletePerson(Person instance);
#endregion

public DataPersonDataContext() : 
    base(global::System.Configuration.ConfigurationManager.ConnectionStrings["msdbConnectionString"].ConnectionString, mappingSource)
{
   OnCreated();
}

public DataPersonDataContext(string connection) : 
    base(connection, mappingSource)
{
   OnCreated();
}

public DataPersonDataContext(System.Data.IDbConnection connection) : 
    base(connection, mappingSource)
{
   OnCreated();
}

public DataPersonDataContext(string connection, System.Data.Linq.Mapping.MappingSource mappingSource) : 
    base(connection, mappingSource)
{
   OnCreated();
}

public DataPersonDataContext(System.Data.IDbConnection connection, System.Data.Linq.Mapping.MappingSource mappingSource) :
    base(connection, mappingSource)
{
   OnCreated();
}

public System.Data.Linq.Table<Person> Person
{
   get
   {
    return this.GetTable<Person>();
   }
}
}
[Table(Name="dbo.Person")]
public partial class Person : INotifyPropertyChanging, INotifyPropertyChanged
{

private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty);

private int _ID;

private string _Name;

private string _Tel;

    #region Extensibility Method Definitions
    partial void OnLoaded();
    partial void OnValidate(System.Data.Linq.ChangeAction action);
    partial void OnCreated();
    partial void OnIDChanging(int value);
    partial void OnIDChanged();
    partial void OnNameChanging(string value);
    partial void OnNameChanged();
    partial void OnTelChanging(string value);
    partial void OnTelChanged();
    #endregion

public Person()
{
   OnCreated();
}

[Column(Storage="_ID", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
public int ID
{
   get
   {
    return this._ID;
   }
   set
   {
    if ((this._ID != value))
    {
     this.OnIDChanging(value);
     this.SendPropertyChanging();
     this._ID = value;
     this.SendPropertyChanged("ID");
     this.OnIDChanged();
    }
   }
}

[Column(Storage="_Name", DbType="NChar(10)")]
public string Name
{
   get
   {
    return this._Name;
   }
   set
   {
    if ((this._Name != value))
    {
     this.OnNameChanging(value);
     this.SendPropertyChanging();
     this._Name = value;
     this.SendPropertyChanged("Name");
     this.OnNameChanged();
    }
   }
}

[Column(Storage="_Tel", DbType="NChar(20)")]
public string Tel
{
   get
   {
    return this._Tel;
   }
   set
   {
    if ((this._Tel != value))
    {
     this.OnTelChanging(value);
     this.SendPropertyChanging();
     this._Tel = value;
     this.SendPropertyChanged("Tel");
     this.OnTelChanged();
    }
   }
}

public event PropertyChangingEventHandler PropertyChanging;

public event PropertyChangedEventHandler PropertyChanged;

protected virtual void SendPropertyChanging()
{
   if ((this.PropertyChanging != null))
   {
    this.PropertyChanging(this, emptyChangingEventArgs);
   }
}

protected virtual void SendPropertyChanged(String propertyName)
{
   if ((this.PropertyChanged != null))
   {
    this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
   }
}
}
#pragma warning restore 1591
3.linq多表查询
sql语句
select t_friend.userid,friendid,truename,formid
from dbo.t_friend left join dbo.t_userinfo
on dbo.t_friend.friendid=dbo.t_userinfo.userid
where dbo.t_friend.userid=5 and applystate=1
linq语句
public void bind()
 {
 blogdatabaseDataContext dc = new blogdatabaseDataContext();
 Table<t_userinfo> login = dc.GetTable<t_userinfo>();
 Table<t_friend> t_f=dc.GetTable<t_friend>();
 var info = from t in t_f
 join c in login on t.friendid equals c.userid
 where( t.userid == 5 && t.applystate == true)
 select new
 {
 t.formid,
 t.userid,
 t.friendid,
 c.truename,
 c.picture
 };
 this.GridView1.DataSource = info;
 this.GridView1.DataBind();
 }