How to switch between “possible” type of an object? [duplicate]

A couple of options:

• If you’re using C# 4, you could use dynamic typing, and split the method into a number of overloads:

  public Uri GetUri(dynamic obj)
  {
      return GetUriImpl(obj);
  }
  
  private Uri GetUriImpl(Entry entry)
  {
      ...
  }
  
  private Uri GetUriImpl(EntryComment comment)
  {
      ...
  }
  

  In this case you’d probably want some sort of “backstop” method in case it’s not a known type.

• You could create a Dictionary<Type, Func<object, Uri>>:

  private static Dictionary<Type, Func<object, Uri>> UriProviders = 
      new Dictionary<Type, Func<object, Uri>> {   
      { typeof(Entry), value => ... },
      { typeof(EntryComment), value => ... },
      { typeof(Blog), value => ... },
  };
  

  and then:

  public Uri GetUri(object obj)
  {
      Func<object, Uri> provider;
      if (!UriProviders.TryGetValue(obj.GetType(), out provider))
      {
          // Handle unknown type case
      }
      return provider(obj);
  }
  

  Note that this won’t cover the case where you receive a subtype of Entry etc.

Neither of these are particularly nice, mind you… I suspect a higher level redesign may be preferable.