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POIs it possible to query custom Attributes in C# during compile time ( not run-time )
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copied!<p>In other words could it be possible to create assembly, which does not even compile (assuming the checking code is not removed ) if each one of the Classes does not have ( "must have" ) custom attributes ( for example Author and Version ) ?</p> <p>Here is the code I have used for querying during run time :</p> <pre><code>using System; using System.Reflection; using System.Collections.Generic; namespace ForceMetaAttributes { [System.AttributeUsage ( System.AttributeTargets.Method, AllowMultiple = true )] class TodoAttribute : System.Attribute { public TodoAttribute ( string message ) { Message = message; } public readonly string Message; } [System.AttributeUsage ( System.AttributeTargets.Class | System.AttributeTargets.Struct, AllowMultiple = true )] public class AttributeClass : System.Attribute { public string Description { get; set; } public string MusHaveVersion { get; set; } public AttributeClass ( string description, string mustHaveVersion ) { Description = description; MusHaveVersion = mustHaveVersion ; } } //eof class [AttributeClass("AuthorName" , "1.0.0")] class ClassToDescribe { [Todo ( " A todo message " )] static void Method () { } } //eof class //how to get this one to fail on compile class AnotherClassToDescribe { } //eof class class QueryApp { public static void Main() { Type type = typeof(ClassToDescribe); AttributeClass objAttributeClass; //Querying Class Attributes foreach (Attribute attr in type.GetCustomAttributes(true)) { objAttributeClass = attr as AttributeClass; if (null != objAttributeClass) { Console.WriteLine("Description of AnyClass:\n{0}", objAttributeClass.Description); } } //Querying Class-Method Attributes foreach(MethodInfo method in type.GetMethods()) { foreach (Attribute attr in method.GetCustomAttributes(true)) { objAttributeClass = attr as AttributeClass; if (null != objAttributeClass) { Console.WriteLine("Description of {0}:\n{1}", method.Name, objAttributeClass.Description); } } } //Querying Class-Field (only public) Attributes foreach(FieldInfo field in type.GetFields()) { foreach (Attribute attr in field.GetCustomAttributes(true)) { objAttributeClass= attr as AttributeClass; if (null != objAttributeClass) { Console.WriteLine("Description of {0}:\n{1}", field.Name,objAttributeClass.Description); } } } Console.WriteLine ( "hit Enter to exit " ); Console.ReadLine (); } //eof Main } //eof class } //eof namespace //uncomment to check whether it works with external namespace //namespace TestNamespace { // class Class1 { } // class Class2 { } //} </code></pre> <p>Edit: Just to justify my choice for answer. I think casperOne provided the correct answer of the question. </p> <p>However the reasons for asking the question seemed to be <a href="https://stackoverflow.com/questions/753255/is-it-possible-to-query-custom-attributes-in-c-during-compile-time-not-run-tim/753301#753301">weak</a>. Probably I should start to use some external tool such as : <a href="http://www.finalbuilder.com/Demos/FinalBuilder_basic_viewlet_swf.html" rel="noreferrer">FinalBuilder</a> or create unit tests checking for this "requirement", using Pex , Nunit or other unit testing frameworks ...</p> <p><strong>EDIT</strong> I added a small <a href="https://stackoverflow.com/questions/753255/is-it-possible-to-query-custom-attributes-in-c-during-compile-time-not-run-tim/763010#763010">code snippet</a> of a console program at the end of the answers that performs the check ... feel free to comment, criticize or suggest improvements<br> Once more I realized that this "requirement" should be implemented as part of the unit testing just before the "check in"</p>

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