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

 

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?

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

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

    • 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 );

    var sortedTable = (from results in resultTable.AsEnumerable()
select (string)results[attributeList]).Distinct().OrderBy(name => name);
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