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    <p>how about this:</p> <pre><code> class ExpandableQueryAttribute : Attribute { private LambdaExpression someLambda; //ctor public ExpandableQueryAttribute(Type hostingType, string filterMethod) { someLambda = (LambdaExpression)hostingType.GetField(filterMethod).GetValue(null); // could also use a static method } } </code></pre> <p>this should let you assign your lambda to a field and then suck it in at runtime, although in general I would prefer to use something like PostSharp to do this at compile time.</p> <p><strong>simple usage example</strong></p> <pre><code> public class LambdaExpressionAttribute : Attribute { public LambdaExpression MyLambda { get; private set; } //ctor public LambdaExpressionAttribute(Type hostingType, string filterMethod) { MyLambda = (LambdaExpression)hostingType.GetField(filterMethod).GetValue(null); } } public class User { public bool IsAdministrator { get; set; } } public static class securityExpresions { public static readonly LambdaExpression IsAdministrator = (Expression&lt;Predicate&lt;User&gt;&gt;)(x =&gt; x.IsAdministrator); public static readonly LambdaExpression IsValid = (Expression&lt;Predicate&lt;User&gt;&gt;)(x =&gt; x != null); public static void CheckAccess(User user) { // only for this POC... never do this in shipping code System.Diagnostics.StackTrace stackTrace = new System.Diagnostics.StackTrace(); var method = stackTrace.GetFrame(1).GetMethod(); var filters = method.GetCustomAttributes(typeof(LambdaExpressionAttribute), true).OfType&lt;LambdaExpressionAttribute&gt;(); foreach (var filter in filters) { if ((bool)filter.MyLambda.Compile().DynamicInvoke(user) == false) { throw new UnauthorizedAccessException("user does not have access to: " + method.Name); } } } } public static class TheClass { [LambdaExpression(typeof(securityExpresions), "IsValid")] public static void ReadSomething(User user, object theThing) { securityExpresions.CheckAccess(user); Console.WriteLine("read something"); } [LambdaExpression(typeof(securityExpresions), "IsAdministrator")] public static void WriteSomething(User user, object theThing) { securityExpresions.CheckAccess(user); Console.WriteLine("wrote something"); } } static void Main(string[] args) { User u = new User(); try { TheClass.ReadSomething(u, new object()); TheClass.WriteSomething(u, new object()); } catch(Exception e) { Console.WriteLine(e); } } </code></pre>
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    1. COcould you add a usage example? up voted in anticipation :)
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    2. CO@ChrisMcCall added a simple example
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    3. COok I get it now, declaring the lambda somewhere else and referring to it by its name... clever!
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