Question

I’ve got a report being built from a dataset. The dataset uses the Sort property to order the data. I know that I can create a sort expression like this:

‘field desc, field2 asc’

But what I need now is a way to do a custom sort. In SQL, I can perform a custom sort by doing something like this:

order by      case when field = 'Some Value' then 0 end     case when field = 'Another Value' then 1 end 

To basically re-define my sort (i.e, Some Value comes before Another Value).

Is it possible to do something similar as a sort expression against a DataView?

Answer 1

Ok, I just whipped this up real quick, and didn’t do all the neccessary error handling and null checking, but it should give you an idea and should be enough to get you started:

public static class DataTableExtensions {     public static DataView ApplySort(this DataTable table, Comparison<DataRow> comparison)     {          DataTable clone = table.Clone();         List<DataRow> rows = new List<DataRow>();         foreach (DataRow row in table.Rows)         {             rows.Add(row);             }          rows.Sort(comparison);          foreach (DataRow row in rows)         {             clone.Rows.Add(row.ItemArray);         }          return clone.DefaultView;     }   } 

Usage:

    DataTable table = new DataTable();     table.Columns.Add('IntValue', typeof(int));     table.Columns.Add('StringValue');      table.Rows.Add(11, 'Eleven');     table.Rows.Add(14, 'Fourteen');     table.Rows.Add(10, 'Ten');     table.Rows.Add(12, 'Twelve');     table.Rows.Add(13, 'Thirteen'); 

//Sort by StringValue:

 DataView sorted = table.ApplySort((r, r2) =>         {             return ((string)r['StringValue']).CompareTo(((string)r2['StringValue']));         }); 

Result:

11 Eleven

14 Fourteen

10 Ten

13 Thirteen

12 Twelve

//Sort by IntValue:

DataView sorted = table.ApplySort((r, r2) =>             {                 return ((int)r['IntValue']).CompareTo(((int)r2['IntValue']));             }); 

Result:

10 Ten

11 Eleven

13 Thirteen

12 Twelve

14 Fourteen

EDIT: Changed it to extension method.

Now in your Lambda, (or you can create a full blown Comparison method) you can do any kind of custom sorting logic that you need. Remember, -1 is less than, 0 is equal to, and 1 is greater than.