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Is it possible to query custom Attributes in C# during compile time ( not run-time )

Asked 2009-04-15T19:10:16.860
25

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 ) ?

Here is the code I have used for querying during run time :

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("De
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1 Answer

4

You can run a post-build step that reflects on the DLL to do what you want.

You will have to write a command-line app that loads the DLL and reflects on the types. You then run that command-line app as a post-build step. I have done this in the past. It is not terribly difficult to do, assuming you understand the reflection API.

PostSharp does this to achieve aspect oriented programming. Pretty cool, actually.

answered 2009-04-15T19:17:03.850

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