LINQ Layer - How To Invoke A Sort Function

 

 Dear all,

I'm trying to create a BLL for an objectdatasource to used for a sorted DataGrid. I am trying to learn about how to use LINQ and I'm sure this is a simple question.

var query = (from p in db.MP3Collections select p).OrderBy(?????????);

 

Now I want to invoke the following method  List<MP3Collection> GetAllMP3s(string sortColumns), which can contain a string name for the field in MP3Collection that is to be sorted (and optionally the "desc" tag).

Now I'm resorting tocoding the query on a case by case basis, which is very tiresome (see the partial code below). This works fine, but is very long and tedious coding. I'm not sure how to go about neatening the code, though am sure it involves the ?????? space above.

Any ideas?

 public static List<MP3Collection> GetAllMP3s(string sortColumns)

{System.Diagnostics.Debug.WriteLine("Pure sort expression: " + sortColumns);

bool descending = false;if (sortColumns.ToLowerInvariant().EndsWith(" desc"))

{

sortColumns = sortColumns.Substring(0, sortColumns.Length - 5);descending = true;

}string[] columnNames = sortColumns.Split(',');

 MP3DataClassesDataContext db = new MP3DataClassesDataContext();

List<MP3Collection> query = (from p in db.MP3Collections select p).OrderByDescending(p => p.fileName).ToList<MP3Collection>();foreach (string columnName in columnNames)

{switch (columnName.Trim().ToLowerInvariant())

{case "filename":if (descending)

{

query = (from p in db.MP3Collections select p).OrderByDescending(p => p.fileName).ToList<MP3Collection>();System.Diagnostics.Debug.WriteLine("Sorting filename descending");

}

else

{query = (from p in db.MP3Collections select p).OrderBy(p => p.fileName).ToList<MP3Collection>();System.Diagnostics.Debug.WriteLine("Sorting filename ascending");

}

break;case "filepath":if (descending)

{

query = (from p in db.MP3Collections select p).OrderByDescending(p => p.filePath).ToList<MP3Collection>();System.Diagnostics.Debug.WriteLine("Sorting filepath descending");

}

else

{query = (from p in db.MP3Collections select p).OrderBy(p => p.filePath).ToList<MP3Collection>();System.Diagnostics.Debug.WriteLine("Sorting filepath ascending");

}

break;

//OTHER CASES HEREdefault:

query = (from p in db.MP3Collections select p).OrderBy(p => p.filePath).ToList<MP3Collection>();

//throw new ArgumentException("SortColumns contains an invalid column name.");break;

}

}

 

//var query = (from p in db.MP3Collections select p).OrderBy(p=>p.fileName).ToList<MP3Collection>();return query;

}