如何处理Entity Framework上的UpdateException-“违反PRIMARY KEY约束"?

问题描述

我有一个允许多个用户使用的应用程序和一个具有2个ID作为复合键的数据库表.这些ID也是来自另一个表的外键.因此，当2个用户尝试将具有相同ID的条目添加到此表中时，其中一个由于主键约束违反而获得UpdateException.我已经发现应该这样处理:

I have an appication that allows multiple users and a database table which has 2 IDs as a compound key. These IDs are also foreign keys from another table.So when 2 users try to add an entry to this tabel with the same IDs one of them gets an UpdateException because of Primary Key constaint violation.I already found out that it should be handled like this:

try
{
    result = base.SaveChanges(options);
}
catch (UpdateException ex)
{
    SqlException innerException = ex.InnerException as SqlException;
    if (innerException != null && innerException.Number == 2627 || innerException.Number == 2601)
    {
        // handle here
    }
    else
    {
        throw;
    }
}

但是我实际上在"//Handle here"部分上做什么.我尝试刷新对象，但是它处于已添加"状态，因此无法刷新.我想做的是:确认已经有一个具有这些ID的对象，删除要插入的对象并从数据库中加载现有对象.我该怎么办?

But what do I actually do on the "//Handle here" part. I tried refreshing the object but it is in the "Added" state and therefor can not be refreshed.What I whant it to do is: Acknowledge that there is already an object with these IDs, drop its object that it wanted to insert and load the existing object from the database.How can I do that?

推荐答案

自从我获得赞成票以来，我就回顾了如何解决这个问题.所以这就是我所做的:

Since I got an upvote I looked back how I solved this. So here is what I did:

// Exception number 2627 = Violation of %ls constraint '%.*ls'. Cannot insert duplicate key in object '%.*ls'.
// Exception number 2601 = Cannot insert duplicate key row in object '%.*ls' with unique index '%.*ls'.
// See http://msdn.microsoft.com/en-us/library/cc645603.aspx for more information and possible exception numbers
if (innerException != null && (innerException.Number == 2627 || innerException.Number == 2601))
{
    // Resolve the primary key conflict by refreshing and letting the store win
    // In order to be able to refresh the entity its state has to be changed from Added to Unchanged
    ObjectStateEntry ose = ex.StateEntries.Single();
    this.ObjectStateManager.ChangeObjectState(ose.Entity, EntityState.Unchanged);
    base.Refresh(RefreshMode.StoreWins, ose.Entity);

    // Refresh addedChanges now to remove the refreshed entry from it
    addedChanges = this.ObjectStateManager.GetObjectStateEntries(System.Data.EntityState.Added).Where(s => !s.IsRelationship);
}
else
{
    throw;
}

---

请注意，从EF 4.1开始， UpdateException 已重命名为 DbUpdateException .

Note that UpdateException has been renamed to DbUpdateException starting with EF 4.1.

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