Question

For the sake of “post processing” on a method, I want to import an extra function into a method.

How can I import a Func that returns an anonymous Type as a parameter for a .Select extension method?

The expression is anounymous like:

p => new
{
    ThumnailUrl = p.PicasaEntry.Media.Thumbnails[0].Attributes["url"],
    ImageUrl = p.PhotoUri
}

and needs to be used at parameter ????? and performed at .Select(?????)

private void BindControl<T, U>(string uri, DataBoundControl target, ?????)
    where T : KindQuery, new()
    where U : PicasaEntity, new()
{
    PicasaFeed feed = CreateFeed<T>(uri);
    albumList.DataSource = GetPicasaEntries<U>(feed).Select(?????);
    albumList.DataBind();
}

update:

finally I want to call it like:

    string albumUri = PicasaQuery.CreatePicasaUri(PicasaUserID, PicasaAlbumID);
    BindControls<AlbumQuery, Album>(albumUri, albumList, ?????);

    string photoUri = PicasaQuery.CreatePicasaUri(PicasaUserID, PicasaAlbumID);
    BindControls<PhotoQuery, Photo>(photoUri, slideShow, ?????);

the other methods are like:

private PicasaFeed CreateFeed<T>(string uri) 
   where T : KindQuery, new()
{
    PicasaFeed feed = null;

    try
    {
        PicasaService service = new PicasaService(PicasaApplicationName);
        T query = new T();
        query.BaseAddress = uri;
        feed = service.Query(query);
    }
    catch (Exception ex)
    {
        //exception handling not shown
    }

    return feed;
}



private IEnumerable<T> GetPicasaEntries<T>(PicasaFeed feed) 
     where T : PicasaEntity, new()
{
    if(feed == null){
        return null;
    }

    IEnumerable<T> entries = null;
    string cacheKey = feed.Id.ToString();

    if(Cache.Get(cacheKey) == null)
    {
        entries = feed.Entries.Select(x => new T() { AtomEntry = x }).ToList();
    Cache.Insert(cacheKey, entries, 
              null, Cache.NoAbsoluteExpiration, new TimeSpan(0,20,0));
    }

    return entries;
}

Answer 1

Anonymous types are really only designed for local use. In a strongly typed language types that can’t be strongly typed are not really encouraged for general use… They are just a part of c#s little dance in the dynamic world.

You have two choices.

Create a strong type.

  class Entry
  {
    public string ThumnailUrl { get; set; }
    public string ImageUrl { get; set; }
  }

And then use :

  p => new Entry 
  {
     ThumnailUrl = p.PicasaEntry.Media.Thumbnails[0].Attributes["url"],
     ImageUrl = p.PhotoUri
  }

Or refer to it as Object. Then use reflection to get the data out – I wouldn’t recommend this.