ASP WebApi query single entity

09 April 2012 brianbruff

 

What’s wrong with this?

 

   1:  public class UsersController : RavenController
   2:  {  
   3:      public User Get(int userId)
   4:      {
   5:          this.AutoSave = false;
   6:          var user = RavenSession.Load<User>(userId);
   7:          if (user == null)
   8:             throw new HttpResponseException("Unable to find user for it " + userId);
   9:          return user;
  10:      }
  11:   
  12:      // GET /api/values
  13:      public IQueryable<User> GetAll()
  14:      {
  15:          this.AutoSave = false;
  16:          return RavenSession.Query<User>();            
  17:      }        
  18:  }

The problem is the variable name used for getting a single user the function would never be called.

E.g. if we put http://localhost:65487/api/users/1 into our browser what will happen is the GetAll gets called!

What we need to call is

   1:  public class UsersController : RavenController
   2:  {  
   3:      public User Get(int id)
   4:      {
   5:          this.AutoSave = false;
   6:          var user = RavenSession.Load<User>(id);
   7:          if (user == null)
   8:              throw new HttpResponseException("Unable to find user for it " + id);
   9:          return user;
  10:      }
  11:   
  12:      // GET /api/values
  13:      public IQueryable<User> GetAll()
  14:      {
  15:          this.AutoSave = false;
  16:          return RavenSession.Query<User>();            
  17:      }        
  18:  }

Now you see that the Get takes a variable name of “id” this is key to getting this work.

 

Note: I’m using IQuerable as this allows me to add some query parameters to my request, e.g.

$filter
A Boolean expression for whether a particular entry should be included in the feed, e.g. Categories?$filter=CategoryName eq 'Produce'. The Query Expression section describes OData expressions.

$orderby
One or more comma-separated expressions with an optional “asc” (the default) or “desc” depending on the order you’d like the values sorted, e.g. Categories?$orderby=CategoryName desc.

$select
Limit the properties on each entry to just those requested, e.g. Categories?$select=CategoryName,Description.

$skip
How many entries you’d like to skip, e.g. Categories?$skip=4.

$top-
Return entries from the top of the feed, e.g. Categories?$top=4

See MSDN for more options.

 

-- Updated Post --

Thanks to James Hancock for pointing this one out for me. This post is a little misleading in that the $select is currently not supported. Please see http://forums.asp.net/t/1771116.aspx/1?OData%20Support for more information on this. The other query string parameters listed above are supported.

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