Paralell execution of DB queries in EF (C# 4.0)

Question

I would like to know if there is a way to replace this syncronized enumeration with something that enumerates both database results in parallel?

I've been doing some research, and as far as I can tell I have to create a new instance of the context for each thread, or perhaps even locking the same context instance until both results are completed (if possible?).

What are my options in .NET 4.0 (C# 4.0)?

using (var context = new DbContext())
{
    IEnumerable<T1> dfd1 = context.T1;
    IEnumerable<T2> dfd2 = context.T2;

    var result1 = dfd1.ToList();
    var result2 = dfd2.ToList();
}

score 1 · Accepted Answer · answered Nov 28 '13 at 13:29

1

Just execute ToList() on two threads, for example using Task.

answered Nov 28 '13 at 13:29

Jakub Konecki

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Is `Task` supported without including any libraries? – Johan Nov 28 '13 at 13:31
Yes, it's part of mscorlib.dll – Jakub Konecki Nov 28 '13 at 13:33
Remember that each task should create its own DbContext – Jens Kloster Nov 28 '13 at 13:34
@JensKloster What about my suggestion about loking one instance. Not possible? – Johan Nov 28 '13 at 13:35
1

@Johan it *is* possible - but EF is [not thread safe](http://stackoverflow.com/questions/6126616/is-dbcontext-thread-safe), so it would be a big risk – Jens Kloster Nov 28 '13 at 13:37

score 0 · Answer 2 · answered Nov 28 '13 at 13:36

0

This probably won't work as is, but something like this may help you get on the way...

public static class Extensions
{
    public static async Task<List<T>> AsyncToList<T>(this IEnumerable<T> enumerable)
    {
        return enumerable.ToList();
    }
}

Usage:

var result = await enumerable.AsyncToList();

answered Nov 28 '13 at 13:36

dav_i

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Ah sorry - you could always use the [BCL](http://blogs.msdn.com/b/bclteam/archive/2012/10/22/using-async-await-without-net-framework-4-5.aspx) to target.NET 4.0 – dav_i Nov 28 '13 at 13:55

Paralell execution of DB queries in EF (C# 4.0)

2 Answers2