Mastering the `let` Keyword in LINQ

In C#, the let keyword in LINQ queries is a neat way to store intermediate results inside a query. It keeps your code clean, readable, and avoids repeated calculations.

How let Works

let allows you to define a temporary variable in your query that you can reuse later:

string[] words = { "one", "two", "three", "four", "five" }; var query = from w in words let length = w.Length where length > 3 select new { Word = w, Length = length }; foreach (var item in query) Console.WriteLine($"{item.Word} - {item.Length}"); 

Output:

three - 5 four - 4 five - 4 

Notice how let avoids repeating w.Length and makes the query cleaner.

Practical Example: Finding Palindromes

string[] words = { "level", "world", "civic", "radar", "test" }; var query = from w in words let reversed = new string(w.Reverse().ToArray()) where w == reversed select w; foreach (var item in query) Console.WriteLine(item); 

Output:

level civic radar 

Here, let stores the reversed string so we can reuse it in the where clause.

Why Use let?

• Reduce Repetition: Calculate once, reuse multiple times.
• Improve Readability: Makes queries easy to understand.
• Easier Maintenance: Change logic in one place.

Quick Tip

let is different from into:

• let = temporary variable inside a query.
• into = continue querying a grouped or joined result.

let is a small feature with a big impact. Start using it in your LINQ queries for cleaner and more efficient C# code.

I’m Morteza Jangjoo and “Explaining things I wish someone had explained to me”