Question

I’m using ravendb as storage backend. Since it uses unit of work pattern I need to open session, perform actions, save results and close session. I want to keep my code clean and don’t call session opening and closing explicitly in each action, so I put this code to OnActionExecuting and OnActionExecuted methods, like this:

    #region RavenDB's specifics

    public IDocumentSession DocumentSession { get; set; }

    protected override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        if (filterContext.IsChildAction)
        {
            return;
        }

        this.DocumentSession = Storage.Instance.OpenSession();
        base.OnActionExecuting(filterContext);
    }

    protected override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        if (filterContext.IsChildAction)
        {
            return;
        }

        if (this.DocumentSession != null && filterContext.Exception == null)
        {
            this.DocumentSession.SaveChanges();
        }

        this.DocumentSession.Dispose();
        base.OnActionExecuted(filterContext);
    }

    #endregion

But some actions require connection to ravendb and come don’t. So I’ve decided to create custom attribute and mark methods need to have DocumentSession opened with it. Here is an example:

    //
    // GET: /Create

    [DataAccess]
    public ActionResult Create()
    {
        return View();
    }

And I stuck. My plan was to retrieve actions’ attributes in the OnActionExecuted method and if [DataAccess] is present, open DocumentSession.

In the OnActionExecuted I can retrieve action name (method’s name) via filterContext.ActionDescriptor.ActionName statement. But how I can retrieve method’s attributes of the given class using reflection?

I found out that it might be Attribute.GetCustomAttributes call, but closest I got — I need to have MemberInfo object of the method. But how I can get this MemberInfo for method given by name?

Answer 1

If you inherit your custom attribute from FilterAttribute, it will have OnActionExecuted and OnActionExecuting methods. And it will be executed before general OnActionExecuted and OnActionExecuting.

Example:

public class DataAccessAttribute: FilterAttribute, IActionFilter
{       

    public void OnActionExecuting(ActionExecutingContext filterContext)
    {
        if (filterContext.IsChildAction)
        {
            return;
        }
        var controller = (YourControllerType)filterContext.Controller;
        controller.DocumentSession = Storage.Instance.OpenSession();
    }

    public void OnActionExecuted(ActionExecutedContext filterContext)
    {
        if (filterContext.IsChildAction)
        {
            return;
        }
        var controller = (YourControllerType)filterContext.Controller;
        documentSession = controller.DocumentSession; 
        if (documentSession != null && filterContext.Exception == null)
        {
            documentSession.SaveChanges();
        }

        documentSession.Dispose();
}