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    <p>Using <a href="http://www.albahari.com/nutshell/predicatebuilder.aspx" rel="nofollow noreferrer">PredicateBuilder</a> (from the authors of LinqPad) you can build up a query from a set of conditions not known at compile time. The following should be sufficient:</p> <pre><code>var predicate = PredicateBuilder.True&lt;Product&gt;(); foreach (Suitability criteria in searchCriteria) { string tempKey = criteria.Key; string tempValue = criteria.Value; predicate = predicate.And(p =&gt; p.Items.Any(s =&gt; s.Key == tempKey &amp;&amp; s.Value == tempValue)); } return dataContext.Products.Where(predicate.Compile()); </code></pre> <p>UPDATE: Heres some sample code that I have tested which works using an IEnumerable as the source, the resulting set <code>productsResult</code> contains the first and second products in <code>products</code> list:</p> <pre><code>var searchCriteria = new List&lt;Suitability&gt;() { new Suitability() { Key="a", Value="b" }, new Suitability() { Key="a", Value="c" } }; var products = new List&lt;Product&gt;() { new Product() { Items = new List&lt;Suitability&gt;() { new Suitability() { Key="a", Value="b" }, new Suitability() { Key="a", Value="c" }} }, new Product() { Items = new List&lt;Suitability&gt;() { new Suitability() { Key="a", Value="b" }, new Suitability() { Key="a", Value="c" }, new Suitability() { Key="b", Value="c" }} }, new Product() { Items = new List&lt;Suitability&gt;() { new Suitability() { Key="c", Value="d" }} } }; var predicate = PredicateBuilder.True&lt;Product&gt;(); foreach (Suitability criteria in searchCriteria) { string tempKey = criteria.Key; string tempValue = criteria.Value; predicate = predicate.And(p =&gt; p.Items.Any( s =&gt; s.Key == tempKey &amp;&amp; s.Value == tempValue)); } IEnumerable&lt;Product&gt; productsResult = products.Where(predicate.Compile()); </code></pre>
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    1. CO@Simon, I tried implementing this but then I remembered I don't have a datacontext as this is not LINQ to SQL and when I apply this to my IEnumerable<Product> list I get an error. Error The type arguments for method 'System.Linq.Enumerable.Where<TSource>(System.Collections.Generic.IEnumerable<TSource>, System.Func<TSource,bool>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
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    2. CO@griegs add .Compile() to get the Func out of the Expression `predicate`...I have updated my answer.
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    3. COI've changed my mind and selected this as the prefered answer. Works a treat thank you. I still have to agree with @Aaronaught that the approach of using the EAV model is not ideal but when you have no alternative...
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