How to Implement Row Numbering within Groups Using LINQ Partitioning?

Row Numbering with LINQ Partitioning

Given a DataTable populated with musicians and their instruments, we desire to emulate the functionality of the MSSQL query using LINQ to determine the positional ordering within each instrument group.

In LINQ, we can accomplish this with a combination of grouping and selection operations:

var orderedBeatles = from b in beatles
                    group b by b.inst into instGroup
                    select new
                    {
                        b.id,
                        b.inst,
                        b.name,
                        rn = instGroup.Count()
                    };

Here, we group the Beatles based on their instruments (inst) and use the Count() method to calculate the row number (rn) for each instrument. We then create an anonymous type for each Beatle, including the original properties as well as the computed row number.

This LINQ query yields the following output:

id |   inst   |   name  | rn
-----------------------------
 1 |  guitar  |  john   | 1
 2 |  guitar  |  george | 2
 3 |  guitar  |  paul   | 3
 4 |  drums   |  ringo  | 1
 5 |  drums   |  pete   | 2

This result mirrors the expected output from the MSSQL query, providing the desired row numbering within instrument groups using LINQ partitioning.

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