CODEWITHSUNDEEP
c#.netwebasp.net-core-mvc
KangJiYoung13
KangJiYoung13

Reputation: 330

How to return an empty viewcomponent MVC 6?

I have searched but I did not find any way to return an empty IViewComponentResult. The only way I managed to do it is by returning an empty View. Is there a better way? This is my code:

public class ClientNavigationViewComponent : ViewComponent
{
    public IViewComponentResult Invoke()
    {
        return User.IsInRole(UserRoles.CLIENT)
            ? View("_ClientMenu")
            : (IViewComponentResult)new EmptyResult();
    }
}

This is the exception:

An exception of type 'System.InvalidCastException' occurred in but was not handled in user code

Additional information: Unable to cast object of type 'Microsoft.AspNet.Mvc.EmptyResult' to type 'Microsoft.AspNet.Mvc.IViewComponentResult'.

I have tried to return null but that won't work too. Any ideas? EDIT Made it work like this:

public class ClientNavigationViewComponent : ViewComponent
{
    public IViewComponentResult Invoke()
    {
        if (User.IsInRole(UserRoles.CLIENT))
            return View("_ClientMenu");
        return new EmptyViewComponent();
    }
}

public class EmptyViewComponent : IViewComponentResult
{
    public void Execute(ViewComponentContext context)
    {
    }

    public Task ExecuteAsync(ViewComponentContext context)
    {
        return Task.FromResult(0);
    }
}

Upvotes: 17

Views: 7138

Answers (2)

david laporte
david laporte

Reputation: 436

You can do the following :

public IViewComponentResult Invoke()
{
  if (User.IsInRole(UserRoles.CLIENT))
     return View("_ClientMenu");

  return Content(string.Empty);
}

Upvotes: 41

Behran Kankul
Behran Kankul

Reputation: 68

A property can inherit from an interface not cast to it.

Try create an object which is inherits from IViewComponentResult. 

public class xyz: IViewComponentResult
{
  // todo
}

then return this object. It should work.

Upvotes: 0

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