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    <p>The difficulty with using Futures with LINQ is that operations like Count execute immediately.</p> <p>As @vandalo found out, <code>Count()</code> after <code>ToFuture()</code> actually runs the Count in memory, which is bad.</p> <p>The only way to get the count in a future LINQ query is to use <code>GroupBy</code> in an invariant field. A good choice would be something that is already part of your filters (like an "IsActive" property)</p> <p>Here's an example assuming you have such a property in Payment:</p> <pre><code>//Create base query. Filters should be specified here. var query = session.Query&lt;Payment&gt;().Where(x =&gt; x.IsActive == 1); //Create a sorted, paged, future query, //that will execute together with other statements var futureResults = query.OrderByDescending(payment =&gt; payment.Created) .Skip((page - 1) * pageSize) .Take(pageSize) .ToFuture(); //Create a Count future query based on the original one. //The paged query will be sent to the server in the same roundtrip. var futureCount = query.GroupBy(x =&gt; x.IsActive) .Select(x =&gt; x.Count()) .ToFutureValue(); //Get the results. var results = futureResults.ToArray(); var count = futureCount.Value; </code></pre> <p>Of course, the alternative is doing two roundtrips, which is not that bad anyway. You can still reuse the original IQueryable, which is useful when you want to do paging in a higher-level layer:</p> <pre><code>//Create base query. Filters should be specified here. var query = session.Query&lt;Payment&gt;(); //Create a sorted, paged query, var pagedQuery = query.OrderByDescending(payment =&gt; payment.Created) .Skip((page - 1) * pageSize) .Take(pageSize); //Get the count from the original query var count = query.Count(); //Get the results. var results = pagedQuery.ToArray(); </code></pre> <p><strong>Update</strong> (2011-02-22): I wrote a <a href="http://sessionfactory.blogspot.com/2011/02/getting-row-count-with-future-linq.html">blog post</a> about this issue and a much better solution.</p>
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    1. USDiego Mijelshon
    1. USDiego Mijelshon
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    1. COthe extension method in your blog post is a very nice solution
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