Book Image

Roslyn Cookbook

Book Image

Roslyn Cookbook

Overview of this book

Open-sourcing the C# and Visual Basic compilers is one of the most appreciated things by the .NET community, especially as it exposes rich code analysis APIs to analyze and edit code. If you want to use Roslyn API to write powerful extensions and contribute to the C# developer tool chain, then this book is for you. Additionally, if you are just a .NET developer and want to use this rich Roslyn-based functionality in Visual Studio to improve the code quality and maintenance of your code base, then this book is also for you. This book is divided into the following broad modules: 1. Writing and consuming analyzers/fixers (Chapters 1 - 5): You will learn to write different categories of Roslyn analyzers and harness and configure analyzers in your C# projects to catch quality, security and performance issues. Moving ahead, you will learn how to improve code maintenance and readability by using code fixes and refactorings and also learn how to write them. 2. Using Roslyn-based agile development features (Chapters 6 and 7): You will learn how to improve developer productivity in Visual Studio by using features such as live unit testing, C# interactive and scripting. 3. Contributing to the C# language and compiler tool chain (Chapters 8 - 10): You will see the power of open-sourcing the Roslyn compiler via the simple steps this book provides; thus, you will contribute a completely new C# language feature and implement it in the Roslyn compiler codebase. Finally, you will write simple command line tools based on the Roslyn service API to analyze and edit C# code.
Table of Contents (19 chapters)
Title Page
Credits
About the Author
Acknowledgments
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Dedication

Implementing a new syntax error in the C# compiler code base


This section will enable Roslyn contributors to make changes to the C# parser to add a new syntax error. The C# parser reports a diagnostic CS0106 (the modifier 'modifier' is not valid for this item) (https://msdn.microsoft.com/en-us/library/3dd3ha66.aspx) when an incorrect modifier is used in symbol declarations such as fields, methods, locals, and so on. For example, the following erroneous code generates three CS0106 instances:

class Class
{
  // Error CS0106: The modifier 'async' is not valid for this item
async int field;

  // Error CS0106: The modifier 'readonly' is not valid for this item               
  readonly static void M()         
  {
    // Error CS0106: The modifier 'readonly' is not valid for this item
    readonly int local = 0;        
    System.Console.WriteLine(local);
  }
}

However, if you declare a parameter with an incorrect modifier, say readonly int param, it doesn't generate CS0106, instead it generates...