C# 使用 Linq-to-SQL 更新记录
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Updating a record using Linq-to-SQL
提问by Andy Link
I do my query...
我做我的查询...
var result = from u in tdc.tblUsers
where u.UserID == userID
select u;
and then I change the values I want to:
然后我更改我想要的值：
foreach (tblUsers u in result)
{
//change values (and no im not changing the primary key or foreign keys)
}
then I submit changes
然后我提交更改
tdc.SubmitChanges();
When it hits submit changes, it throws exception that the row wasn't found or was changed. I am the only person using this so there's no other conflicts with accessing the db or locking. Why would it throw the ChangeConflictException? I have stepped through with debugger and the data persists all the way through the process, including the changes that I'm trying to make.
当它点击提交更改时，它会抛出该行未找到或已更改的异常。我是唯一使用它的人，因此访问数据库或锁定没有其他冲突。为什么会抛出ChangeConflictException？我已经通过调试器逐步完成，并且数据在整个过程中一直存在，包括我尝试进行的更改。
I have also tried it this way before and got the same error
我以前也试过这种方式，得到了同样的错误
tblUsers result = (from u in tdc.tblUsers
where u.UserID == userID
select u).Single();
result.Address = address;
result.Phone = phone;
tdc.SubmitChanges();
It will only ever retrieve 1 record with this query since UserIDis the primary key.
由于UserID是主键，因此它只会使用此查询检索 1 条记录。
I've done this many times and it has worked. Every example I've found is exactly what I have.
我已经这样做了很多次，并且奏效了。我找到的每个例子都正是我所拥有的。
回答by Sascha
Maybe you work with different context? Try to encapsulate it by using
也许你在不同的环境下工作？尝试使用封装它
using (myContext ctx = new myContext())
{
var user = ctx.users.first();
user.name="blah";
ctx.SubmitChanges();
}
回答by EricRRichards
Quite often, if you look at the actual SQL that Linq-to-SQL generates, you'll see that it is being really over-zealous with matching the database row that you initially retrieved. Imagine that you have a table with columns ID(PK), A, B, C. You would think that if you updated column C for a row, it should be sufficient to update the row with a matching primary key. But what often happens is that Linq-to-SQL is also trying to match on columns A and B as well. Normally, that's fine. Unless you have concurrent writes, either from multi-threading or multi-processes, and something else modifies column A or B for the record that you are trying to update. Then you get these System.Data.Linq.ChangeConflictException: Row not found or changed. errors when you call SubmitChanges() on your data context.
很多时候，如果您查看 Linq-to-SQL 生成的实际 SQL，您会发现它非常热衷于匹配您最初检索的数据库行。想象一下，您有一个包含 ID(PK)、A、B、C 列的表。您会认为，如果您为某行更新了 C 列，那么使用匹配的主键更新该行就足够了。但经常发生的是，Linq-to-SQL 也试图匹配 A 列和 B 列。通常，这很好。除非您有并发写入，无论是来自多线程还是多进程，并且其他内容修改了您尝试更新的记录的 A 列或 B 列。然后你会得到这些 System.Data.Linq.ChangeConflictException: Row not found or changed。在数据上下文中调用 SubmitChanges() 时出错。
