实体框架似乎用它们的实际值替换参数

Question

We're seeing a whole bunch of SQL errors in our logs about Must declare the scalar variable "@" or some such thing. Tracing into the actual SQL that generates the error, it appears these are SQL statement that the Entity Framework generates. Here's an example:

SELECT TOP (1) 
    [Extent1].[AccountId] AS [AccountId], 
    [Extent1].[Username] AS [Username], 
    [Extent1].[EmployerId] AS [EmployerId], 
    [Extent1].[EmployeeId] AS [EmployeeId], 
    [Extent1].[SubscriberId] AS [SubscriberId], 
    [Extent1].[RelationshipCode] AS [RelationshipCode], 
    [Extent1].[AccountType] AS [AccountType], 
    [Extent1].[AccountStatus] AS [AccountStatus]
    FROM [dbo].[jc_Accounts] AS [Extent1]
    WHERE (@'Brunswick' = [Extent1].[Username]) OR ((@'Brunswick' IS NULL) AND ([Extent1].[Username] IS NULL))

The thing causing the error is that @'Brunswick' line, which is supposed to be the Username we're looking for. So, it's as if the Entity Framework is swapping @p0 or something with the actual value. We're also seeing tons of errors about things like @2892734 or some such, so numeric parameters are also affected. For example:

WHERE ([Extent4].[AreaLevel] = 2) AND ([Extent1].[DimensionId] = [Extent4].[AreaId]) AND ([Extent5].[GroupId] = @106929) AND ([Extent5].[IsActive] = 1) AND ([Extent5].[AreaId] = [Extent1].[DimensionId])

Unfortunately, our database context and entity repository code is something you'd see in your worst nightmare. A lot of it hasn't been touched in years, there's wrappers around wrappers around wrappers, things that use reflection to map POCOs to stored procedure calls, all sorts of fun stuff. We've spent a ton of time on this and we haven't found anything that can shed some light on this issue.

We've also upgraded Entity Framework from 4 to 5 to 6 and other versions in between, and this bug persists. So I don't think it's a weird EF bug.

My Question:

In what case would EF generate such a query? Or, if it's for sure some sort of custom thing we've extended the Entity Framework into doing, what sorts of extensions would I want to start looking at? I'm looking for things I could search the code base for and get some clues.

I don't need a full answer, I'm looking for some ideas from EF experts to get me headed down the right track. I can add more details, just ask below.

Answer 1

It's weird indeed. Even though you might not want to change your context, would it be reasonable to temporarily add some custom logging to it? Earlier today I happened to give that example in another post :

public MyContext : DbContext
{
    private static ILog log = LogManager.GetCurrentClassLogger();

    public MyContext(string connectionString)
        : base(connectionString)
    {
        this.Database.Log = (msg) => log.Trace(msg);
    }
}

However, very temporarily, and in debug if you can reproduce the query, you could do something like that to break when it happens then crawl up the callstack :

public MyContext : DbContext
{
    private static ILog log = LogManager.GetCurrentClassLogger();

    public MyContext(string connectionString)
        : base(connectionString)
    {
        this.Database.Log = (msg) => 
        {
            if (msg.Contains("@'Brunswick'"))
                Debugger.Break();
        };
    }
}

If you fancy regex, or if you don't always get the same variable substitution, you could make msg match against "@ that isn't followed by 'p__linq__'", but I'll leave that to you!

Answer 2

If i'm not mistaken, i already saw some of this and it was situation where we used for example Take(20) instead of Take(()=>20)

or another case is var a = []{'a','b','c'} var res = context.Users.Where(u=>a.contains(u.Id))