LINQ Interview Question #36

What is the difference between ThenBy and another OrderBy?

Filtering, Projection, Ordering & Element Operators Junior Beginner

Quick Interview Answer

ThenBy adds a secondary ascending sort to an existing ordering. Another OrderBy starts a new primary ordering and can replace the significance of the previous ordering.

Detailed Explanation

ThenBy adds a secondary ascending sort to an existing ordering. Another OrderBy starts a new primary ordering and can replace the significance of the previous ordering.

Use ThenBy or ThenByDescending when records with the same primary key need a predictable secondary order.

Code Example

var result = employees
    .OrderBy(e => e.Department)
    .ThenBy(e => e.LastName)
    .ThenBy(e => e.FirstName);