let-clause.md

description	title	ms.date	f1_keywords	helpviewer_keywords	ms.assetid
let clause - C# Reference	let clause	07/20/2015	let_CSharpKeyword let	let keyword [C#] let clause [C#]	13c9c1a4-ce57-48ef-8e1b-4c2a59b99fb4

let clause (C# Reference)

In a query expression, it's sometimes useful to store the result of a subexpression in order to use it in subsequent clauses. You can do this with the let keyword, which creates a new range variable and initializes it with the result of the expression you supply. Once initialized with a value, the range variable can't be used to store another value. However, if the range variable holds a queryable type, it can be queried.

Example

In the following example let is used in two ways:

1. To create an enumerable type that can itself be queried.

2. To enable the query to call ToLower only one time on the range variable word. Without using let, you would have to call ToLower in each predicate in the where clause.

[!code-csharpcscsrefQueryKeywords#28]

See also

• Query Keywords (LINQ)
• LINQ in C#
• Language Integrated Query (LINQ)
• Handle exceptions in query expressions