partial void DeleteCustomers(Customers instance);
partial void UpdateCustomers(Customers instance);
void CreateCustomer(Customers customer)
{
ctx.Customers.InsertOnSubmit(customer);
ctx.SubmitChanges();//立即提交
}
partial void InsertCustomers(Customers instance);
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
//检测并发
////<一>默认，总是检查 列特性UpdateCheck=UpdateCheck.Always
////修改Db，使测试环境更明朗sql=update Products set UnitPrice=25,UnitsInStock=38 where CategoryID=1
//var products = from p in ctx.Product where p.CategoryID == 1 select p;
//foreach (Product p in products)
//{
// p.UnitsInStock =Convert.ToInt16(p.UnitsInStock - 1);//库存减1
//}
////程序提交之前，执行sql=update Products set UnitPrice=UnitPrice+1,UnitsInStock=UnitsInStock-2 where CategoryID=1 --执行完后UnitPrice=26，UnitsInStock=36
//ctx.SubmitChanges();//执行此处时，抛System.Data.Linq.ChangeConflictException {"找不到行或行已更改。"} ,数据库数据由sql更改，程序未更改
////<二>从不检查 列特UpdateCheck=UpdateCheck.Never
////修改Db，使测试环境更明朗sql=update Products set UnitPrice=25,UnitsInStock=38 where CategoryID=1
//var products = from p in ctx.Product where p.CategoryID == 1 select p;
//foreach (Product p in products)
//{
// p.UnitsInStock = Convert.ToInt16(p.UnitsInStock - 1);//库存减1
//}
////程序提交之前，执行sql=update Products set UnitPrice=UnitPrice+1,UnitsInStock=UnitsInStock-2 where CategoryID=1 --执行完后UnitPrice=26，UnitsInStock=36
//ctx.SubmitChanges();//执行结果为： UnitPrice=27，由sql语句的update生效，但UnitsInStock=37，此处程序的SubmitChanges覆盖了sql语句的update这个字段。
////<三>仅在已更改对象后检查。 列特UpdateCheck=UpdateCheck.WhenChanged
////修改Db，使测试环境更明朗sql=update Products set UnitPrice=25,UnitsInStock=38 where CategoryID=1
//var products = from p in ctx.Product where p.CategoryID == 1 select p;
//foreach (Product p in products)
//{
// p.UnitsInStock = Convert.ToInt16(p.UnitsInStock - 1);//库存减1
//}
////程序提交之前，执行sql=update Products set UnitPrice=UnitPrice+1,UnitsInStock=UnitsInStock-2 where CategoryID=1 --执行完后UnitPrice=26，UnitsInStock=36
//ctx.SubmitChanges();//执行此处时，抛System.Data.Linq.ChangeConflictException {"找不到行或行已更改。"} ,数据库数据由sql更改，程序未更改
//有以上三种情况，当列特UpdateCheck=UpdateCheck.Never 是会导致数据并发
//解决并发
////方法一：Resolve(RefreshMode.OverwriteCurrentValues);放弃当前更新，所有更新以原先更新为准
////修改Db，使测试环境更明朗sql=update Products set UnitPrice=25,UnitsInStock=38 where CategoryID=1
//var products = from p in ctx.Product where p.CategoryID == 1 select p;
//foreach (Product p in products)
//{
// p.UnitsInStock = Convert.ToInt16(p.UnitsInStock - 1);//库存减1
//}
//try
//{
// ctx.SubmitChanges(ConflictMode.ContinueOnConflict);//程序提交之前，执行sql=update Products set UnitPrice=UnitPrice+1,UnitsInStock=UnitsInStock-2 where CategoryID=1 --执行完后UnitPrice=26，UnitsInStock=36
//}
//catch (ChangeConflictException)
//{
// foreach (ObjectChangeConflict cc in ctx.ChangeConflicts)
// {
// Product product = (Product)cc.Object;
// Response.Write(product.ProductID + "<br>");
// cc.Resolve(RefreshMode.OverwriteCurrentValues); // 放弃当前更新，所有更新以原先更新为准 执行结果：UnitPrice=26，UnitsInStock=36，放弃当前程序更新
// }
//}
////方法二：Resolve(RefreshMode.KeepChanges); 原先更新有效，冲突字段以当前更新为准
////修改Db，使测试环境更明朗sql=update Products set UnitPrice=25,UnitsInStock=38 where CategoryID=1
//var products = from p in ctx.Product where p.CategoryID == 1 select p;
//foreach (Product p in products)
//{
// p.UnitsInStock = Convert.ToInt16(p.UnitsInStock - 1);//库存减1
//}
//try
//{
// ctx.SubmitChanges(ConflictMode.ContinueOnConflict);//程序提交之前，执行sql=update Products set UnitPrice=UnitPrice+1,UnitsInStock=UnitsInStock-2 where CategoryID=1 --执行完后UnitPrice=26，UnitsInStock=36
//}
//catch (ChangeConflictException)
//{
// foreach (ObjectChangeConflict cc in ctx.ChangeConflicts)
// {
// Product product = (Product)cc.Object;
// Response.Write(product.ProductID + "<br>");
// cc.Resolve(RefreshMode.KeepChanges);// 原先更新有效，冲突字段以当前更新为准 执行结果：UnitPrice=26，UnitsInStock=36，放弃当前程序更新
// }
//}
//方法三：Resolve(RefreshMode.KeepCurrentValues);放弃原先更新，所有更新以当前更新为准
//修改Db，使测试环境更明朗sql=update Products set UnitPrice=25,UnitsInStock=38 where CategoryID=1
//var products = from p in ctx.Product where p.CategoryID == 1 select p;
//foreach (Product p in products)
//{
// p.UnitsInStock = Convert.ToInt16(p.UnitsInStock - 1);//库存减1
//}
//try
//{
// ctx.SubmitChanges(ConflictMode.ContinueOnConflict);//程序提交之前，执行sql=update Products set UnitPrice=UnitPrice+1,UnitsInStock=UnitsInStock-2 where CategoryID=1 --执行完后UnitPrice=26，UnitsInStock=36
//}
//catch (ChangeConflictException)
//{
// foreach (ObjectChangeConflict cc in ctx.ChangeConflicts)
// {
// Product product = (Product)cc.Object;
// Response.Write(product.ProductID + "<br>");
// cc.Resolve(RefreshMode.KeepCurrentValues);// 放弃原先更新，所有更新以当前更新为准 执行结果：UnitPrice=26，UnitsInStock=36，放弃当前程序更新
// }
//}
//事务
//Customers customer=new Customers();
//customer.CustomerID="Rock";
//customer.CompanyName="RockHe";
//Customers customer2=new Customers();
//customer2.CustomerID="BOLID";
//customer2.CompanyName="Good";
//ctx.Customers.InsertOnSubmit(customer);
//ctx.Customers.InsertOnSubmit(customer2);
//try
//{
// ctx.SubmitChanges();//更新DB select * from Customers where CustomerID='Rock'查询为空, linq to sql 会把当前上下午做一次事务提交，所以当第二条数据条件失败时会导致整个上下文（DataContext）提交失败
//}
//catch (Exception ex)
//{
// //throw;
//}
//解决上面问题，可以把每次加入做成一个事务
Customers customer3 = new Customers();
customer3.CustomerID = "Rock";
customer3.CompanyName = "RockHe";
Customers customer4 = new Customers();
customer4.CustomerID = "BOLID";
customer4.CompanyName = "Good";
CreateCustomer(customer3);
CreateCustomer(customer4);
}
}
