What are the applications of C# lambda expressions?

C# lambda expressions can be used in the following scenarios:

1. LINQ query: Lambda expressions can be used to define query conditions, sorting methods, and projection operations, among other tasks. They are a common syntax form in LINQ queries.
2. Delegation and event handling: Lambda expressions can be used to define anonymous methods, to be passed as parameters of delegate types, or for defining event handlers.
3. Collection operations: Lambda expressions can be used to filter, sort, map, and aggregate collections.
4. Parallel programming: Lambda expressions can be used to define the code for tasks or threads in parallel programming.
5. Expression trees: Lambda expressions can be used to create and manipulate expression trees, which are used to generate dynamic code.
6. Dynamic types: Lambda expressions can be used to define and invoke methods of dynamic types.
7. Unit testing and mock objects: Lambda expressions can be used to define anonymous methods in unit testing, or to mimic objects’ behavior.

In general, Lambda expressions can be used in any situation where defining an anonymous method or expression is needed, providing a concise, flexible, and easy-to-understand syntax.