How do I get a distinct, ordered list of names from a DataTable using LINQ?

Question

I have a DataTable with a Name column. I want to generate a collection of the unique names ordered alphabetically. The following query ignores the order by clause.

var names =     (from DataRow dr in dataTable.Rows     orderby (string)dr["Name"]     select (string)dr["Name"]).Distinct(); 

Why does the orderby not get enforced?

Answer 1

The problem is that the Distinct operator does not grant that it will maintain the original order of values.

So your query will need to work like this

var names = (from DataRow dr in dataTable.Rows              select (string)dr["Name"]).Distinct().OrderBy( name => name ); 

Answer 2

To make it more readable and maintainable, you can also split it up into multiple LINQ statements.

1. First, select your data into a new list, let's call it x1, do a projection if desired
2. Next, create a distinct list, from x1 into x2, using whatever distinction you require
3. Finally, create an ordered list, from x2 into x3, sorting by whatever you desire