CODEWITHSUNDEEP
c#linq
berko
berko

Reputation: 2975

How can I test that my Linq IQueryable has executed

I am currently using Linq to NHibernate (although that is not an issue with regards to this question) to execute queries against my database and I want to be able to test whether the current IQueryable result instance has been executed or not.

The debugger knows that my IQueryable has not been 'invoked' because it tells me that expanding the Results property will 'enumerate' it. Is there a way for me to programmatically identify that as well.

I hope that makes sense :)

Upvotes: 5

Views: 3592

Answers (3)

Christian Hagelid
Christian Hagelid

Reputation: 8355

I believe you can use DataContext.Log to log everything that is executed.

Upvotes: 0

dcstraw
dcstraw

Reputation: 3311

How about writing an IQueryable wrapper like this:

class QueryableWrapper<T> : IQueryable<T>
{
    private IQueryable<T> _InnerQueryable;
    private bool _HasExecuted;

    public QueryableWrapper(IQueryable<T> innerQueryable)
    {
        _InnerQueryable = innerQueryable;
    }

    public bool HasExecuted
    {
        get
        {
            return _HasExecuted;
        }
    }

    public IEnumerator<T> GetEnumerator()
    {
        _HasExecuted = true;

        return _InnerQueryable.GetEnumerator();
    }

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    public Type ElementType
    {
        get { return _InnerQueryable.ElementType; }
    }

    public System.Linq.Expressions.Expression Expression
    {
        get { return _InnerQueryable.Expression; }
    }

    public IQueryProvider Provider
    {
        get { return _InnerQueryable.Provider; }
    }
}

Then you can use it like this:

var query = new QueryableWrapper<string>(
    from str in myDataSource
    select str);

Debug.WriteLine("HasExecuted: " + query.HasExecuted.ToString());

foreach (string str in query)
{
    Debug.WriteLine(str);
}

Debug.WriteLine("HasExecuted: " + query.HasExecuted.ToString());

Output is:

False
String0
String1
...
True

Upvotes: 3

Mark Pattison
Mark Pattison

Reputation: 3029

Assuming you're using Visual Studio, you can insert DataContext.Log = Console.Out into your code. You can then watch the SQL as it's executed, in the output window.

I'm not sure whether it's possible to programatically test whether the query has been executed. You can force it to execute, for example by calling .ToList on the query.

Upvotes: 0

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