Question

Today, I was cleaning up some of my code with FXCop and it complained about a Attribute class I had with this violation.

CA1019: Define accessor for attribute argument.

On this page, http://msdn.microsoft.com/en-us/library/ms182136.aspx there is more information, but I still do not get the reason for this as it seems to me more verbose and less relevant.

It gives two codes samples.

using System;

namespace DesignLibrary
{
// Violates rule: DefineAccessorsForAttributeArguments.

[AttributeUsage(AttributeTargets.All)]
public sealed class BadCustomAttribute :Attribute 
{
  string data;

  // Missing the property that corresponds to 
  // the someStringData parameter.

  public BadCustomAttribute(string someStringData)
  {
     data = someStringData;
  }
}


// Satisfies rule: Attributes should have accessors for all arguments.
[AttributeUsage(AttributeTargets.All)]
public sealed class GoodCustomAttribute :Attribute 
{
   string data;

   public GoodCustomAttribute(string someStringData)
   {
      data = someStringData;
   }
   //The constructor parameter and property
   //name are the same except for case.

   public string SomeStringData
   {
      get 
      {
         return data;
      }
   }
}
}

I don’t understand why the SomeStringData property is required. Isn’t the someStringData a parameter? Why does it need to have its own property if it is already stored in another property?

Actually, mine is a little different as it looks like this.

[AttributeUsage(AttributeTargets.Property)]
public sealed class ExampleAttribute : Attribute
{
    public ExampleAttribute(string attributeValue)
    {
        this.Path = attributeValue;
    }

    public string Name
    {
        get;
        set;
    }

    // Add to add this to stop the CA1019 moaning but I find it useless and stupid?
    public string AttributeValue
    {
        get
        {
            return this.Name;
        }
    }
}

Rather than a private field, I have used a public autoproperty, I had to add the last part to make the warning stop but I don’t see the point and it also adds another public field to this class, which is redundant, and seems less clean.

That said, I assume that this warning is raised for a reason so what good reason I am missing here?

Thanks in advance.

Answer 1

FxCop is complaining because your existing property doesn’t match the parameter name.
Therefore, it doesn’t realize that the parameter actually is exposed.

You should rename the property or parameter to match (except for case), or suppress the warning.