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.

Answer 1

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