Overload Index() Method in MVC Controller

Question

I want to access both /Blog and /Blog/1 where "1" is the ID of the Blog. Here is my code:

    '
    ' GET: /Blog/

    Function Index() As ViewResult
        Return (View(db.Blogs.ToList()))
    End Function

    '
    ' GET: /Blog/(Integer)

    Function Index(id As Integer) As ViewResult
        Dim blog As Blog = db.Blogs.Find(id)
        Return View("Details", "_MyLayout", blog)
    End Function

It gives the error:

Server Error in '/' Application.

The current request for action 'Index' on controller type 'BlogController' is ambiguous between the following action methods: System.Web.Mvc.ViewResult Index() on type GemcoBlog.GemcoBlog.BlogController System.Web.Mvc.ViewResult Index(Int32) on type GemcoBlog.GemcoBlog.BlogController

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Reflection.AmbiguousMatchException: The current request for action 'Index' on controller type 'BlogController' is ambiguous between the following action methods: System.Web.Mvc.ViewResult Index() on type GemcoBlog.GemcoBlog.BlogController System.Web.Mvc.ViewResult Index(Int32) on type GemcoBlog.GemcoBlog.BlogController

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

How can I overload the Index() method?

Edit:

I am also trying to combine them like so:

    '
    ' GET: /Blog/

    Function Index(id As Integer) As ViewResult
        If (id) Then
            Dim blog As Blog = db.Blogs.Find(id)
            'Return View(blog)
            Return View("Details", "_MyLayout", blog)
        Else
            Return (View(db.Blogs.ToList()))
        End If
        'Return View(db.Blogs.Where(Function(x) x.Name = "Test").ToList())
    End Function

However, the error I get is:

Server Error in '/' Application.

The parameters dictionary contains a null entry for parameter 'id' of non-nullable type 'System.Int32' for method 'System.Web.Mvc.ViewResult Index(Int32)' in 'Blog.Blog.BlogController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter. Parameter name: parameters

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ArgumentException: The parameters dictionary contains a null entry for parameter 'id' of non-nullable type 'System.Int32' for method 'System.Web.Mvc.ViewResult Index(Int32)' in 'Blog.Blog.BlogController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter. Parameter name: parameters

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Darin Dimitrov · Accepted Answer · 2012-07-26 16:20:17Z

2

You cannot have 2 actions on the same controller accessible with the same HTTP verb. So either change the action name or you will have to disambiguate using different HTTP verbs. For example:

<HttpPost>
Function Index(id As Integer) As ViewResult
    Dim blog As Blog = db.Blogs.Find(id)
    Return View("Details", "_MyLayout", blog)
End Function

But since the other action also seems to be fetching data I guess that you don't want to make it POST accessible only. So simply rename it in this case. Sticking to standard RESTful conventions you could use Index for returning a list of resources and Show to return a particular resource:

Function Index() As ViewResult
    Return (View(db.Blogs.ToList()))
End Function

'
' GET: /Blog/(Integer)

Function Show(id As Integer) As ViewResult
    Dim blog As Blog = db.Blogs.Find(id)
    Return View("Details", "_MyLayout", blog)
End Function

answered Jul 26, 2012 at 16:20

Darin Dimitrov

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2 Comments

user1477388 Over a year ago

Wouldn't that mean the URL would have to be /Blog/Show/1 instead of Blog/1? What if I just combine them into one method. I updated the question with new code, but it too gives me an error.

Darin Dimitrov Over a year ago

You could make the Show action default in your routing configuration in Global.asax: action = "Show" instead of action = "Index". Now you can use /Blog/123. And no, don't combine the 2 into a single action. That would be bad design decision.

Erik Funkenbusch · Accepted Answer · 2012-07-26 16:59:39Z

2

There are a couple of ways you could do this. The easiest would be to rename the first method to "ShowBlog" or whatever you want, then setup a route in your global.asax that routes to the /Blog route without a parameter.

For example (in c#):

routes.MapRoute("Blog", "Blog", new { controller = "Blog", action = "ShowBlog" });

Make sure the MapRoute comes before the default route.

To make your second method work, you would need to make the id nullable, and then check for null in your method.

answered Jul 26, 2012 at 16:59

Erik Funkenbusch

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Comments

Paolo del Mundo · Accepted Answer · 2012-07-26 16:58:52Z

1

Since it is not nullable, it automatically assumes you are providing an id by default. Make the Id a Nullable Integer, and it will work for both URLs.

Function Index(id As Nullabe( Of Integer )) As ViewResult

answered Jul 26, 2012 at 16:58

Paolo del Mundo

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Comments

Stephen Davies · Accepted Answer · 2014-08-20 02:14:01Z

0

Small amendment to Erik's post to make it work (I am using MVC4)

routes.MapRoute("Blog", "Blog/{id}", new { controller = "Blog", action = "ShowBlog" });

answered Aug 20, 2014 at 2:14

Stephen Davies

1

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