What is Diagnostic/Code Analyzer?
To put it simply it is something similar to Resharper or Telerik JustCode. It analyzes codes while writing on code editor and suggest for improvements of codes through Squiggles, light icon and based on various severity.
How it works?
I had mentioned that it is similar to Resharper and Telerik JustCode but internal infrastructure is completely different.
It is dependent on new compiler Roslyn. Roslyn has a clever compile technique, unlike older version which makes it faster and flexible for dynamic compilation without the need of the entire code base. The structure is basically divided into two categories Syntax Tree, and Semantic Model. The syntax tree is related to syntaxes only it does not require any reference check. It can be related to DOM elements structure in case of HTML. Syntax Tree consists of very fine details as simple as WhiteSpace under the code. The Semantic Model is kind of references of Syntax Tree in which it tries to resolve any dependencies of that code. Syntax tree analysis is very cheap in comparison to Semantic model. This is where Code Analyzer can be much more efficient in comparison of Resharper and Telerik JustCode versions.
What are benefits?
If you remember old FxCop or StyleCop, it used to get warnings, messages, and errors after building the application where as Analyzer works on Roslyn with Syntax Tree, through which we can see live status of codes. These also give Tooltips to quickly Refactor the code. In comparison of Resharper and Telerik JustCode, it is much faster since it has to depend on the certain area of code via Syntax tree and only referenced items of same through the Semantic model.
The other great benefit is since it does not need to depend on any tool, all team can follow same common decided conventions. In a case of ReSharper or other VS tools it may have inconsistency since team members can choose not to use that tool. It can be implemented through NuGet which means it would be available on source code and all team member has to follow the same convention.
How to use?
It is compatible with .Net Framework and Core version as well. All you need to do is to install your favorite Analyzer through NuGet and done. There are already tons of library available on NuGet Package Manager. Have a look on various libraries for same https://www.nuget.org/packages?q=C%23+tags%3Aanalyzers and use based on convention, style, library and technology.
The good old StyleCop and FxCop is being recreated to leverage Analyzers let us have a look on the usage of StyleCop.
This is all it requires.
The rules can be tweaked as needed based on Rule identifier available for each and every error or messages. These are optional.
To do that need to put under project.json
These are the configuration files which can be configured as needed. Based on above given path it has to reside on root level.
<?xml version="1.0" encoding="utf-8"?>
<RuleSet Name="New Rule Set" Description=" " ToolsVersion="14.0">
<Rules AnalyzerId="StyleCop.Analyzers" RuleNamespace="StyleCop.Analyzers">
<Rule Id="SA0000" Action="Error" />
<Rule Id="SA1005" Action="None" />
<Rule Id="SA1028" Action="None" />
<Rule Id="SA1101" Action="None" />
<Rule Id="SA1200" Action="None" />
<Rule Id="SA1208" Action="None" />
<Rule Id="SA1210" Action="None" />
<Rule Id="SA1633" Action="None" />
<Rule Id="SA1124" Action="None" />
<Rule Id="SA1649" Action="None" />
<Rule Id="SA1401" Action="None" />
<Rule Id="SA1513" Action="None" />
<Rule Id="SA1512" Action="None" />
<Rule Id="SA1202" Action="None" />
<Rule Id="SA1108" Action="None" />
<Rule Id="SA1116" Action="None" />
Some other analyzers: