MVC Web API 2 - Using custom attribute on action

Question

I am attempting to create a custom ActionFilterAttribute as shown. The attribute will only contain a property of Path.

public class TestLinkAttribute : ActionFilterAttribute
{
    public string Path { get; set; }

    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {

    }
}

I would like to be able to access this attribute on the help pages area that web api integrates similar to this.

<td class="api-testLink">
@{ 
var attrColl = api.ActionDescriptor.GetCustomAttributes<TestLinkAttribute>();
      if(attrColl.Count > 0)
      {
          <p>@attrColl[0].Path</p>
      }
}
</td>

I decorated the action like this.

 [TestLink(Path = "api/surveys/72469282/responses")]
 public string GetQuestions(int id)
 {
 }

This is completely new territory to me and i have done a bit of research but can't / don't know if there is a quick way to accomplish this. Currently the output is empty as the attribute collection is never > 0

I've built a simple version of this, creating a custom attribute, assigning it to an Action and then pulling the attribute out to display a Path property like you've shown. It all works in my sample solution. Are you able to provide an example that does not work and host it on e.g. Github? — Kirk Larkin
– Kirk Larkin, Commented Sep 1, 2017 at 12:42
Unfortunately I can't at the moment. It's an internal app and the company is very strict about hosting this type of thing externally. — Eric
– Eric, Commented Sep 1, 2017 at 16:24
Is there any chance something else is necessary because I am trying to access the attribute within the help area of this application and something with reflection? I can do this no problem outside of that area. — Eric
– Eric, Commented Sep 1, 2017 at 16:27
I can't think of anything else. Chances are the problem is in something that's not detailed in your question. — Kirk Larkin
– Kirk Larkin, Commented Sep 1, 2017 at 18:05

Eric · Accepted Answer · 2017-09-06 16:45:56Z

6

After further research, you must inherit from System.Web.Http.Filters when you create the custom attribute with a controller inheriting from ApiController. I was inheriting from the standard mvc ActionFilterAttribute from MVC namespace (System.Web.MVC).

using System.Web.Http.Filters;

namespace App.Extensions
{
    public class TestLinkAttribute : ActionFilterAttribute
    {
        public string Path { get; set; }

    }
}

Now when i access the attribute from the ApiGroup.cshtml in the HelpPage area, i can use the following it it will properly obtain the value.

var attrColl = api.ActionDescriptor.GetCustomAttributes<TestLinkAttribute>();

edited Sep 6, 2017 at 16:45

answered Sep 5, 2017 at 20:10

Eric

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