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POHow to Transform a LINQ Expression when you do not have one of the parameters when you define it
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  1. POHow to Transform a LINQ Expression when you do not have one of the parameters when you define it
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    copied!<p>I'm trying to build more generic query functionality into my application. What I'd like to do is define objects which given an predicate expression can apply that to an iqueryable with a value that will be passed in later.</p> <p>I believe the code below should demonstrate what I'm trying to do well enough to understand the problem. Please let me know if you'd like more details!</p> <p>Thanks!</p> <pre><code>//in practice the value of this would be set in object constructor likely private Expression&lt;Func&lt;Contact, string, bool&gt;&gt; FilterDefinition = (c, val) =&gt; c.CompanyName.Contains(val); //this needs to filter the contacts using the FilterDefinition and the filterValue. Filterval needs to become the string parameter private IQueryable&lt;Contact&gt; ApplyFilter(IQueryable&lt;Contact&gt; contacts, string filterValue) { //this method is what I do know know how to contruct. // I need to take the FilterDefinition expression and create a new expression that would be the result if 'filtervalue' had been passed into it when it was created. //ie the result would be (if 'mycompany' was the value of filterValue) an expression of // c =&gt; c.CompanyName.Contains("mycompany") Expression&lt;Func&lt;Contact, bool&gt;&gt; usableFilter = InjectParametersIntoCriteria(FilterDefinition, "SomeCompanyName"); //which I could use the results of to filter my full results. return contacts.Where(usableFilter); } </code></pre>
 

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