問題描述

我想為想要從 linq2sql 遷移到 linq2entities 和 ADO.net 實體框架(此處稱為 L2E)的人們提供參考.我不想討論這兩個哪個更好.我只想為想要從一個過渡到另一個的人創(chuàng)建一個列表，列出這兩者之間的差異.

I'd like to start a reference for people who want to move from linq2sql to linq2entities and the ADO.net Entity Framework (in here called L2E). I don't want to discuss which of these two is better. I just want to create a list of differences between these two for people who want to transition from one to the other.

基本的東西很簡單:刪除 linq2sql 數(shù)據(jù)類，添加 ado.net 模型(從數(shù)據(jù)庫創(chuàng)建).將實體"重命名為之前數(shù)據(jù)上下文的名稱.

The basic stuff is easy: remove the linq2sql data classes, add ado.net model (created from database). Rename 'Entities' to the name of the former datacontext.

using (MyDataClassesDataContext mydc = new MyDataClassesDataContext())
{
  // change data
  mydc.SubmitChanges();
}

在 L2E 中，這必須更改為:

In L2E this would have to be changed to:

using (MyDataClassesDataContext mydc = new MyDataClassesDataContext())
{
  // change data
  mydc.SaveChanges();
}

using (MyDataClassesDataContext mydc = new MyDataClassesDataContext())
{
  MyTable myRow = new MyTable();
  mydc.MyTable.InsertOnSubmit(myRow);
  mydc.SubmitChanges();
}

在 L2E 中，這必須更改為:

In L2E this would have to be changed to:

using (MyDataClassesDataContext mydc = new MyDataClassesDataContext())
{
  MyTable myRow = new MyTable(); // or = MyTable.CreateMyTable(...);
  mydc.AddToMyTable(myRow);
  mydc.SaveChanges();
}    

mydc.MyTable.Attach(myRow);

在 L2E 中:

// you can use either
mydc.Attach(myRow);
// or (have not tested this)
mydc.AttachTo("MyTable", myRow);

mydc.MyTable.Attach(myRow, myOriginalRow);

在 L2E 中(MSDN - 應用對分離對象所做的更改):

mydc.Attach(myOriginalRow);
mydc.ApplyPropertyChanges(myOriginalRow.EntityKey.EntitySetName, myRow);

mydc.MyTable.DeleteOnSubmit(myRow);

在 L2E 中:

mydc.DeleteObject(myRow);

mydc.Log = Console.Out;
// before mydc.SubmitChanges();

在 L2E 中，您可以顯示查詢的 SQL(感謝 TFD):

In L2E you can show the SQL for a query (thanks to TFD):

using System.Data.Objects;
...
var sqlQuery = query as ObjectQuery;
var sqlTrace = sqlQuery.ToTraceString();

遺憾的是，我發(fā)現(xiàn)無法輸出為調(diào)用 SaveChanges() 生成的 SQL - 您需要使用 用于此目的的 SQL 分析器.

Sadly, I found no way to output the SQL generated for a call to SaveChanges() - you'd need to use a SQL profiler for this.

if (!mydc.DatabaseExists())
  mydc.CreateDatabase();

在 L2E 中:

// according to TFD there are no DDL commands in L2E

mydc.ExecuteCommand("ALTER TABLE dbo.MyTable ADD CONSTRAINT DF_MyTable_ID DEFAULT (newid()) FOR MyTableID");

在 L2E 中:

要對 EF 中的數(shù)據(jù)庫執(zhí)行 eSQL 命令(請注意，eSQL 尚不支持 DDL 或 DML(更改、插入、更新、刪除)命令):

To execute an eSQL command against the database in EF (beware, eSQL does not support DDL or DML (alter, Insert, update, delete) commands yet):

using System.Data.EntityClient;
...
EntityConnection conn = this.Connection as EntityConnection;
using (EntityCommand cmd = conn.CreateCommand())
{
  conn.Open();
  cmd.CommandText = @"Select t.MyValue From MyEntities.MyTable As t";
  var result = cmd.ExecuteReader(System.Data.CommandBehavior.SequentialAccess);
  result.Read();
  var myValue = result.GetValue(0);
  ...
  conn.Close();
}

命令文本在 Entity SQL 中，與 T-SQL 不是 100% 相同.
(感謝 TFD)

The command text is in Entity SQL which is not 100% the same as T-SQL.
(thanks to TFD)

如果您需要在同一連接上使用 DDL/DML 命令，您可能需要自己創(chuàng)建數(shù)據(jù)庫連接，使用您自制的 db 連接連接 EF，并將此連接用于您的 DML 命令.不漂亮，自己看看:

If you need DDL/DML commands on the same connection, you might need to create the database connection yourself, connect the EF using your selfmade db connection, and use this connection for your DML commands. Not pretty, have a look for yourself:

MetadataWorkspace workspace = new MetadataWorkspace(new string[] { "res://*/" }, new Assembly[] { Assembly.GetExecutingAssembly() });
using (SqlConnection sqlConnection = new SqlConnection("Data Source=salsa;Initial Catalog=SamAlyza;Integrated Security=True"))
using (EntityConnection econ = new EntityConnection(workspace, sqlConnection))
using (AlyzaDataClassesDataContext adc = new AlyzaDataClassesDataContext(econ))
{
   // now you can use the SqlConnection like always
}

partial void OnCreated()
{
  Name = "";
}

在 L2E 中，你可以為你的表類創(chuàng)建一個默認的構(gòu)造函數(shù):

In L2E you can just create a default constructor for your table class:

partial class MyTable
{
  public MyTable()
  {
    Name = "";
  }
}

CREATE TABLE dbo.[MyTable]
(
 [MyTableID] uniqueidentifier NOT NULL ROWGUIDCOL CONSTRAINT [PK_MyTable] PRIMARY KEY,
 [Name] nvarchar(100) NOT NULL,
)  ON [PRIMARY]

ALTER TABLE dbo.[MyTable] ADD CONSTRAINT [DF_MyTable_ID] DEFAULT (newid()) FOR [MyTableID]


CREATE TABLE dbo.[MySubTable]
(
 [MySubTableID] uniqueidentifier NOT NULL ROWGUIDCOL CONSTRAINT [PK_MySubTable] PRIMARY KEY,
 [MyTableID] uniqueidentifier NULL,
 [Subname] decimal(18,2) NOT NULL,
)  ON [PRIMARY]

ALTER TABLE dbo.[MySubTable] ADD CONSTRAINT [DF_MySubTable_ID] DEFAULT (newid()) FOR [MySubTableID]

ALTER TABLE dbo.[MySubTable] ADD CONSTRAINT [FK_MySubTable_MyTable] FOREIGN KEY
(
 [MyTableID]
) REFERENCES dbo.[MyTable]
(
 [MyTableID]
) ON DELETE CASCADE

  MyTable myRow = new MyTable();
  myRow.MySubTable.Add(new MySubTable());
  mydc.MyTable.InsertOnSubmit(myRow);

在 L2E 中非常相似:

Very similar in L2E:

  MyTable myRow = new MyTable();
  myRow.MySubTable.Add(new MySubTable());
  mydc.AddToSaLyWebsites(test);

from u in adc.MySubTable 
where u.MyTableID == _searchForTableID && u.Name == _searchForName 
select u

from u in adc.MySubTable 
where u.MyTable.MyTableID == _searchForTableID && u.Name == _searchForName 
select u

from u in _searchForTable.MySubTable
where u.Name == _searchForName
select u

from t in mydc.MyTable 
where t.Date >= _searchForDate && t.Date <= _searchForDate.AddHours(2) 
select t;

DateTime endDate = _searchForDate.AddHours(2);
from t in mydc.MyTable 
where t.Date >= _searchForDate && t.Date <= endDate 
select t;

using System.Data.Objects;
...
var sqlQuery = query as ObjectQuery<T>;
var sqlTrace = sqlQuery.ToTraceString();