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


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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?


Alle Antworten
  • Translate

    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

  • Translate

    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 );
    

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

  • Translate

    Try out the following:

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

  • Translate

    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.


  • Translate

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

    OrderBy needs to be the final operation.


  • Translate

    You can use something like that:

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