5. Querying Any Collection Easily with LINQ | Functional C#

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Functional C#

By : Wisnu Anggoro

5 (3)

Functional C#

5 (3)

By: Wisnu Anggoro

Overview of this book

Functional programming makes your application faster, improves performance, and increases your productivity. C# code is written at a higher level of abstraction, so that code will be closer to business requirements, abstracting away many low-level implementation details. This book bridges the language gap for C# developers by showing you how to create and consume functional constructs in C#. We also bridge the domain gap by showing how functional constructs can be applied in business scenarios. We’ll take you through lambda expressions and extension methods, and help you develop a deep understanding of the concepts and practices of LINQ and recursion in C#. By the end of the book, you will be able to write code using the best approach and will be able to perform unit testing in functional programming, changing how you write your applications and revolutionizing your projects.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Tasting Functional Style in C#

1. Tasting Functional Style in C#

Introducing functional programming

Comparison between functional and imperative programming

Preparing the C# compiler

Concepts of functional programming

Feeling functional in C#

Transforming imperative code to functional code

The advantages and disadvantages of functional programming

Summary

2. Walkthrough Delegates

2. Walkthrough Delegates

Introducing delegates

Built-in delegates

Distinguishing variance in delegates

Summary

3. Expressing Anonymous Methods with Lambda Expressions

3. Expressing Anonymous Methods with Lambda Expressions

Getting to know anonymous methods

Lambda expressions

Subscribing for events using lambda expressions

The advantages of using lambda expression in functional programming

Summary

4. Extending Object Functionality with Extension Methods

4. Extending Object Functionality with Extension Methods

Getting closer to extension methods

Calling extension methods in the other assemblies

Leveraging the interface, collection, and object

Advantages of using extension methods in functional programming

Limitations of the extension method

Summary

5. Querying Any Collection Easily with LINQ

5. Querying Any Collection Easily with LINQ

Getting started with LINQ

Deferring LINQ execution

Choosing between fluent syntax and query expression syntax

Enumerating standard query operators

Summary

6. Enhancing the Responsiveness of the Functional Program with Asynchronous Programming

6. Enhancing the Responsiveness of the Functional Program with Asynchronous Programming

Building a responsive application

The asynchronous programming model pattern

The task-based asynchronous pattern

Asynchronous programming with the async and await keywords

Asynchronous functions in functional programming

Summary

7. Learning Recursion

7. Learning Recursion

Exploring recursion

Using tail recursion

Recursion in a functional approach using LINQ Aggregate

Summary

8. Optimizing the Code using Laziness and Caching Techniques

8. Optimizing the Code using Laziness and Caching Techniques

Introduction to laziness

Caching expensive resources

Summary

9. Working with Pattern

9. Working with Pattern

Dissecting pattern matching in functional programming

Introducing Monad as a design pattern

Summary

10. Taking an Action in C# Functional Programming

10. Taking an Action in C# Functional Programming

Developing functional programming in Windows forms

Summary

11. Coding Best Practice and Testing the Functional Code

11. Coding Best Practice and Testing the Functional Code

Coding best practices in functional C#

Separating the code from domain logic and mutable shell

Summary

Choosing between fluent syntax and query expression syntax

From our preceding discussion, we found two types of querying syntaxes so far. Let's discuss this further by distinguishing these two syntaxes.

IEnumerable<int> queryInt = 
  intList.Select(i => i * 2); 
int queryIntCount = queryInt.Count();

The preceding code snippet is the fluent syntax type. We invoke the Select and Count operators by invoking their extension method in the Enumerable class. Using the fluent syntax, we can also chain the method so it will approach functional programming as follows:

IEnumerable<int> queryInt = 
  intList 
    .Select(i => i * 2); 
    .Count();

Another syntax type we can use in querying data in LINQ is query expression syntax. We applied this syntax type when we discussed deferred execution in the previous topic. The code snippet of the query expression syntax is as follows:

IEnumerable<Member> memberQuery = 
  from m in memberList ...

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