Overload Index() Method in MVC Controller - asp.net-mvc

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

Answer 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.

Answer 3

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

Answer 4

Small amendment to Erik's post to make it work (I am using MVC4)
routes.MapRoute("Blog", "Blog/{id}", new { controller = "Blog", action = "ShowBlog" });