entity framework 新增，更新，事务

protected void Button1_Click(object sender, EventArgs e)
{
yyEntities _db;
_db = new yyEntities();

test t = new test();
t.testName = this.TextBox1.Text;
t.testCon = this.TextBox2.Text;
_db.AddObject("test", t);
_db.SaveChanges();

//using (var edm = new yyEntities())
//{

// test c = new test { testName = "c2", testCon = "成都市2" };
// edm.AddObject("test", c);
// int result = edm.SaveChanges();
//}

}

其中，在代码中，需要注意的是：AddObject方法中参数“entitySetName ”就是指对应实体名称，应该是：“Customers”，而不是“NorthwindEntities.Customers”；

l　更新：

using (var edm = new NorthwindEntities())

{

Customers addc = edm.Customers.FirstOrDefault(cc => cc.CustomerID == "c2");

addc.City = "CD";

addc.ContactName = "cnblogs";

addc.Country = "CN";

int result = edm.SaveChanges();

Assert.AreEqual　(result, 1);

Customers updatec = edm.Customers.FirstOrDefault(cc => cc.CustomerID == "c2");

Console.WriteLine("CustomerId={0},City={1}", updatec.CustomerID, updatec.City);

}

其中，需要注意的是：不能去更新主键，否则会报“System.InvalidOperationException : 属性“xxx”是对象的键信息的一部分，不能修改。”

l　删除：

实例代码如下：

using (var edm = new NorthwindEntities())

{

Customers deletec = edm.Customers.FirstOrDefault(cc => cc.CustomerID == "c2");

edm.DeleteObject(deletec);

int result = edm.SaveChanges();

Assert.AreEqual　(result, 1);

Customers c = edm.Customers.FirstOrDefault(cc => cc.CustomerID == "c2");

Assert.AreEqual　(c, null　);

}

l　事务：

实例代码如下：

NorthwindEntities edm = null　;

System.Data.Common.DbTransaction tran = null　;

try

{

edm = new NorthwindEntities();

edm.Connection.Open();

tran = edm.Connection.BeginTransaction();

Customers cst = edm.Customers.FirstOrDefault(cc => cc.CustomerID == "c#");

cst.Country = "CN";

cst.City = "CD";

edm.SaveChanges();

tran.Commit();

}
catch (Exception ex)
{
if (tran != null　)
tran.Rollback();
throw ex;
}
finally
{
if (edm != null　&& edm.Connection.State != System.Data.ConnectionState.Closed)
edm.Connection.Close();
}

//  Skip(N) ,跳过前N条，Take(m)  ,取m条数据

var c=edm.Customers.OrderBy(c=>c.CustomerId).Skip(30).Take(20);//30-50