Workaround for C# generic attribute limitation

Question

As discussed here, C# doesn\'t support generic attribute declaration. So, I\'m not allowed to do something like:

[Audit (UserAction.Update)]
publ         


        

Answer 1

You have at least these three possibilities:

1. You could use reflection to call LoadById
2. You could create an expression tree that calls LoadById
3. You could provide a LoadById method in your repository that is not generic.

Answer 2

You could use reflection to load by id:

public class AuditAttribute : Attribute
{
    public AuditAttribute(Type t)
    {
        this.Type = t;
    }

    public  Type Type { get; set; }

    public void DoSomething()
    {
        //type is not Entity
        if (!typeof(Entity).IsAssignableFrom(Type))
            throw new Exception();

        int _id;

        IRepository myRepository = new Repository();
        MethodInfo loadByIdMethod =  myRepository.GetType().GetMethod("LoadById");
        MethodInfo methodWithTypeArgument = loadByIdMethod.MakeGenericMethod(this.Type);
        Entity myEntity = (Entity)methodWithTypeArgument.Invoke(myRepository, new object[] { _id });
    }
}

Answer 3

You could use reflection to invoke the LoadById method. The following msdn article should point you in the right direction:

http://msdn.microsoft.com/en-us/library/b8ytshk6(v=vs.100).aspx