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

Answer 3

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

Answer 4

Try out the following:

dataTable.Rows.Cast<DataRow>().select(dr => dr["Name"].ToString()).Distinct().OrderBy(name => name);

Answer 5

Try the following

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

this should work for what you need.

Answer 6

To abstract: all of the answers have something in common.

OrderBy needs to be the final operation.

Answer 7

You can use something like that:

dataTable.Rows.Cast<DataRow>().GroupBy(g => g["Name"]).Select(s => s.First()).OrderBy(o => o["Name"]);