Question

So for this example lets say I have a DataTable which is called dt and it has some number of columns, I want to get back a list of the column names and how many different values are in each column. Also I would like the result set ordered by the largest to the smallest

For example I have a table with 4 columns and 40 rows of data, in the first column there is 4 distinct values, second column 12, third column 20, fourth column 40. I want my result set to look like this

Column4 40
Column3 20
Column2 12
Column1 4

How could I achieve this using C# and Linq?

Answer 1

Your LINQ code

var result = dt.Columns
    .Cast<DataColumn>()
    .Select(dc => new {
        Name = dc.ColumnName,
        Values = dt.Rows
            .Cast<DataRow>()
            .Select(row => row[dc])
            .Distinct()
            .Count()})
    .OrderBy(item => item.Values);