In order to create a Roslyn Analyzer project, you need to install the .NET Compiler Platform SDK via the Visual Studio Installer. There are two different ways to find the .NET Compiler Platform SDK in the Visual Studio Installer:<\/p>\n
Install using the Visual Studio Installer \u2013 Workloads view:<\/p>\n
- \n
- Run the Visual Studio Installer and select Modify.\n<\/br>
![\"Visual](\"https:\/\/devblogs.microsoft.com\/dotnet\/wp-content\/uploads\/sites\/10\/2022\/03\/visual-studio-installer.png\")
<\/li>\n<\/br><\/p>\n
- Check the Visual Studio extension development workload.\n<\/br>
![\"Visual](\"https:\/\/devblogs.microsoft.com\/dotnet\/wp-content\/uploads\/sites\/10\/2022\/03\/visual-studio-extension-development.png\")
<\/li>\n<\/ol>\nInstall using the Visual Studio Installer – Individual components tab:<\/p>\n
- \n
- Run the Visual Studio Installer and select Modify.<\/li>\n
<\/br><\/p>\n
- Select the Individual components tab.<\/li>\n
<\/br><\/p>\n
- Check the box for .NET Compiler Platform SDK.\n<\/br>
![\"Visual](\"https:\/\/devblogs.microsoft.com\/dotnet\/wp-content\/uploads\/sites\/10\/2022\/03\/visual-studio-individual-components.png\")
<\/li>\n<\/ol>\n<\/br><\/p>\n
Writing an analyzer<\/strong><\/p>\n
Let\u2019s begin by creating a syntax tree analyzer. This analyzer generates a syntax warning for any statement that is not enclosed in a block that has curly braces
{<\/code> and}<\/code>. For example, the following code generates a warning for both theif<\/code>-statement and theSystem.Console.WriteLine<\/code> invocation statement, but thewhile<\/code> statement is not flagged:<\/p>\n<\/br>
![\"Brace](\"https:\/\/devblogs.microsoft.com\/dotnet\/wp-content\/uploads\/sites\/10\/2022\/03\/brace-diagnostic.png\")
<\/p>\n- \n
- Open Visual Studio.<\/li>\n
<\/br><\/p>\n
- On the Create a new project dialog search VSIX and select Analyzer with Code Fix (.NET Standard)<\/strong> in C# and click Next.\n<\/br>
![\"Create](\"https:\/\/devblogs.microsoft.com\/dotnet\/wp-content\/uploads\/sites\/10\/2022\/03\/create-new-project-dialog.png\")
<\/li>\n<\/br><\/p>\n
- Name your project BraceAnalyzer<\/strong> and click OK. The solution should contain 3 projects: BraceAnalyzer, BraceAnalyzer.Test, BraceAnalyzer.Vsix.\n<\/br>
![\"Analyzer](\"https:\/\/devblogs.microsoft.com\/dotnet\/wp-content\/uploads\/sites\/10\/2022\/03\/analyzer-solution-layout.png\")
\n <\/br><\/p>\n- \n
- BraceAnalyzer: This is the core analyzer project that contains the default analyzer implementation that reports a diagnostic for all type names that contain any lowercase letter.<\/li>\n
- BraceAnalyzer.Test: This is a unit test project that lets you make sure your analyzer is producing the right diagnostics and fixes.<\/li>\n
- BraceAnalyzer. Vsix: The VSIX project bundles the analyzer into an extension package (.vsix file). This is the startup project in the solution.<\/li>\n<\/ul>\n<\/li>\n
<\/br><\/p>\n
- In the Solution Explorer, open Resources.resx<\/strong> in the BraceAnalyzer project. This displays the resource editor. <\/li>\n
<\/br><\/p>\n
- Replace the existing resource string values for AnalyzerDescription, AnalyzerMessageFormat, and AnalyzerTitle with the following strings:\n <\/br><\/p>\n
- \n
- Change AnalyzerDescription to
Enclose statement with curly braces<\/code>.<\/li>\n- Change AnalyzerMessageFormat to
`{` brace expected<\/code>.<\/li>\n- Change AnalyzerTitle to
Enclose statement with curly braces<\/code>. <\/li>\n<\/ul>\n<\/br>\n
![\"Resources](\"https:\/\/devblogs.microsoft.com\/dotnet\/wp-content\/uploads\/sites\/10\/2022\/03\/resources-resx.png\")
\n<\/li>\n<\/br><\/p>\n
- Within the BraceAnalyzerAnalyzer.cs file, replace the Initialize method implementation with the following code:<\/li>\n
<\/br><\/p>\n
public override void Initialize(AnalysisContext context)\n{\n context.RegisterSyntaxTreeAction(syntaxTreeContext =>\n {\n \/\/ Iterate through all statements in the tree\n var root = syntaxTreeContext.Tree.GetRoot(syntaxTreeContext.CancellationToken);\n foreach (var statement in root.DescendantNodes().OfType<StatementSyntax>())\n {\n \/\/ Skip analyzing block statements \n if (statement is BlockSyntax)\n {\n continue;\n }\n\n \/\/ Report issues for all statements that are nested within a statement\n \/\/ but not a block statement\n if (statement.Parent is StatementSyntax && !(statement.Parent is BlockSyntax))\n {\n var diagnostic = Diagnostic.Create(Rule, statement.GetFirstToken().GetLocation());\n syntaxTreeContext.ReportDiagnostic(diagnostic);\n }\n }\n });\n}<\/pre>\n<\/br><\/p>\n
- Check your progress by pressing F5 to run your analyzer. Make sure that the BraceAnalyzer.Vsix project is the startup project before pressing F5. Running the VSIX project loads an experimental instance of Visual Studio, which lets Visual Studio keep track of a separate set of Visual Studio extensions. <\/li>\n
<\/br><\/p>\n
- In the Visual Studio instance, create a new C# class library with the following code to verify that the analyzer diagnostic is neither reported for the method block nor the
while<\/code> statement, but is reported for theif<\/code> statement andSystem.Console.WriteLine<\/code> invocation statement:\n<\/br> <\/li>\n<\/br><\/p>\n
- Now, add curly braces around the
System.Console.WriteLine<\/code> invocation statement and verify that the only single warning is now reported for theif<\/code> statement:\n<\/br>![\"Brace](\"https:\/\/devblogs.microsoft.com\/dotnet\/wp-content\/uploads\/sites\/10\/2022\/03\/brace-diagnostic-for-if-statement.png\")
<\/li>\n<\/ol>\n<\/br><\/p>\n
Writing a code fix<\/strong><\/p>\n
An analyzer can provide one or more code fixes. A code fix defines an edit that addresses the reported issue. For the analyzer that you created, you can provide a code fix that encloses a statement with a curly brace.<\/p>\n
- \n
- Open the BraceAnalyzerCodeFixProvider.cs file. This code fix is already wired up to the Diagnostic ID produced by your diagnostic analyzer, but it doesn’t yet implement the right code transform. <\/li>\n
<\/br><\/p>\n
- Change the title string to \u201cAdd brace”: <\/li>\n
<\/br><\/p>\n
private const string title = \"Add brace\";<\/pre>\n
<\/br><\/p>\n
- Change the following line to register a code fix. Your fix will create a new document that results from adding braces.<\/li>\n
<\/br><\/p>\n
context.RegisterCodeFix(\n CodeAction.Create(\n title: title,\n createChangedDocument: c => AddBracesAsync(context.Document, diagnostic, root),\n equivalenceKey: title),\n diagnostic);<\/pre>\n
<\/br><\/p>\n
- You’ll notice red squiggles in the code you just added on the
AddBracesAsync<\/code> symbol. Add a declaration forAddBracesAsync<\/code> by replacing theMakeUpperCaseAsync<\/code> method with the following code: <\/li>\n<\/br><\/p>\n
Task<Document>
AddBracesAsync(Document document, Diagnostic diagnostic, SyntaxNode root)\n {\n var statement = root.FindNode(diagnostic.Location.SourceSpan).FirstAncestorOrSelf<StatementSyntax>();\n var newRoot = root.ReplaceNode(statement, SyntaxFactory.Block(statement));\n return Task.FromResult(document.WithSyntaxRoot(newRoot));\n }<\/pre>\n <\/br><\/p>\n
- Press F5 to run the analyzer project in a second instance of Visual Studio. Place your cursor on the diagnostic and press (Ctrl+.<\/strong>) to trigger the Quick Actions and Refactorings<\/strong> menu. Notice your code fix to add a brace!\n<\/br>
![\"Image](\"https:\/\/devblogs.microsoft.com\/dotnet\/wp-content\/uploads\/sites\/10\/2020\/03\/brace-analyzer-code-fix2.png\")
<\/li>\n<\/ol>\n<\/br><\/p>\n
- Press F5 to run the analyzer project in a second instance of Visual Studio. Place your cursor on the diagnostic and press (Ctrl+.<\/strong>) to trigger the Quick Actions and Refactorings<\/strong> menu. Notice your code fix to add a brace!\n<\/br>
- Change AnalyzerMessageFormat to
- Replace the existing resource string values for AnalyzerDescription, AnalyzerMessageFormat, and AnalyzerTitle with the following strings:\n <\/br><\/p>\n
- Name your project BraceAnalyzer<\/strong> and click OK. The solution should contain 3 projects: BraceAnalyzer, BraceAnalyzer.Test, BraceAnalyzer.Vsix.\n<\/br>
- Open Visual Studio.<\/li>\n
- Run the Visual Studio Installer and select Modify.<\/li>\n