LINQ中的数据冲突

Question

使用时进行更改时SubmitChanges(),LINQ有时会因ChangeConflictException错误消息Row not found or changed而异常死机,并且没有任何指示具有冲突的行或具有冲突更改的字段,当另一个用户更改了该行中的某些数据时.

有没有办法确定哪一行存在冲突以及它们出现在哪些字段中,还有一种方法可以让LINQ忽略该问题并简单地提交数据吗？

此外,是否有人知道当行中的任何数据发生更改时,或者仅在LINQ尝试更改的字段中更改了数据时是否发生此异常？

Answer 1

这是一种查看冲突位置的方法(这是一个MSDN示例,因此您需要进行大量自定义):

try
{
    db.SubmitChanges(ConflictMode.ContinueOnConflict);
}
catch (ChangeConflictException e)
{
    Console.WriteLine("Optimistic concurrency error.");
    Console.WriteLine(e.Message);
    Console.ReadLine();
    foreach (ObjectChangeConflict occ in db.ChangeConflicts)
    {
        MetaTable metatable = db.Mapping.GetTable(occ.Object.GetType());
        Customer entityInConflict = (Customer)occ.Object;
        Console.WriteLine("Table name: {0}", metatable.TableName);
        Console.Write("Customer ID: ");
        Console.WriteLine(entityInConflict.CustomerID);
        foreach (MemberChangeConflict mcc in occ.MemberConflicts)
        {
            object currVal = mcc.CurrentValue;
            object origVal = mcc.OriginalValue;
            object databaseVal = mcc.DatabaseValue;
            MemberInfo mi = mcc.Member;
            Console.WriteLine("Member: {0}", mi.Name);
            Console.WriteLine("current value: {0}", currVal);
            Console.WriteLine("original value: {0}", origVal);
            Console.WriteLine("database value: {0}", databaseVal);
        }
    }
}

无论如何要使它忽略问题并提交:

db.SubmitChanges(ConflictMode.ContinueOnConflict);

Answer 2

这些(您可以在您的datacontext的部分类中添加它们可能有助于您了解其工作原理:

public void SubmitKeepChanges()
{
    try
    {
        this.SubmitChanges(ConflictMode.ContinueOnConflict);
    }
    catch (ChangeConflictException e)
    {
        foreach (ObjectChangeConflict occ in this.ChangeConflicts)
        {
            //Keep current values that have changed, 
//updates other values with database values

            occ.Resolve(RefreshMode.KeepChanges);
        }
    }
}

public void SubmitOverwrite()
{
    try
    {
        this.SubmitChanges(ConflictMode.ContinueOnConflict);
    }
    catch (ChangeConflictException e)
    {
        foreach (ObjectChangeConflict occ in this.ChangeConflicts)
        {
            // All database values overwrite current values with 
//values from database

            occ.Resolve(RefreshMode.OverwriteCurrentValues);
        }
    }
}

public void SubmitKeepCurrent()
{
    try
    {
        this.SubmitChanges(ConflictMode.ContinueOnConflict);
    }
    catch (ChangeConflictException e)
    {
        foreach (ObjectChangeConflict occ in this.ChangeConflicts)
        {
            //Swap the original values with the values retrieved from the database. No current value is modified
            occ.Resolve(RefreshMode.KeepCurrentValues);
        }
    }
}