Analyze source code with Roslyn

Introspective analysis of an analyzer in C#

Create a new Console Application
Add the NuGet package Microsoft.CodeAnalysis
Import the namespaces Microsoft.CodeAnalysis.MSBuild, System.Linq and Microsoft.CodeAnalysis.CSharp.Syntax
Write the following example code in the Main method:

// Declaring a variable with the current project file path.
const string projectPath = @"C:\<your path to the project\<project file name>.csproj";

// Creating a build workspace.
var workspace = MSBuildWorkspace.Create();
        
// Opening this project.
var project = workspace.OpenProjectAsync(projectPath).Result;

// Getting the compilation.
var compilation = project.GetCompilationAsync().Result;

// As this is a simple single file program, the first syntax tree will be the current file.
var syntaxTree = compilation.SyntaxTrees.First();

// Getting the root node of the file.
var rootSyntaxNode = syntaxTree.GetRootAsync().Result;

// Finding all the local variable declarations in this file and picking the first one.
var firstLocalVariablesDeclaration = rootSyntaxNode.DescendantNodesAndSelf().OfType<LocalDeclarationStatementSyntax>().First();

// Getting the first declared variable in the declaration syntax.
var firstVariable = firstLocalVariablesDeclaration.Declaration.Variables.First();

// Getting the text of the initialized value.
var variableInitializer = firstVariable.Initializer.Value.GetFirstToken().ValueText;

// This will print to screen the value assigned to the projectPath variable.
Console.WriteLine(variableInitializer);

Console.ReadKey();

When running the project, you will see the variable declared on top printed to the screen. This means that you successfully self analysed a project and found a variable in it.

Analyze a simple “Hello World” application in C#

Create a new console application with one line in the Main method: Console.WriteLine("Hello World")

Remember the path to the .csproj file and replace it in the example.

Create a new Console Application and install the Microsoft.CodeAnalysis NuGet package and try the following code:

const string projectPath = @"C:\HelloWorldApplication\HelloWorldProject.csproj";

// Creating a build workspace.
var workspace = MSBuildWorkspace.Create();
        
// Opening the Hello World project.
var project = workspace.OpenProjectAsync(projectPath).Result;

// Getting the compilation.
var compilation = project.GetCompilationAsync().Result;

foreach (var tree in compilation.SyntaxTrees)
{
    Console.WriteLine(tree.FilePath);

    var rootSyntaxNode = tree.GetRootAsync().Result;

    foreach (var node in rootSyntaxNode.DescendantNodes())
    {
        Console.WriteLine($" *** {node.Kind()}");
        Console.WriteLine($"     {node}");
    }
}

Console.ReadKey();

This will print all the files and all the syntax nodes in your Hello World project.

Analyze a simple “Hello World” application in VB.NET

Create a new console application with one line in the Main method: Console.WriteLine("Hello World")

Remember the path to the .vbproj file and replace it in the example.

Create a new Console Application and install the Microsoft.CodeAnalysis NuGet package and try the following code:

Const projectPath = "C:\HelloWorldApplication\HelloWorldProject.vbproj"

' Creating a build workspace.
Dim workspace = MSBuildWorkspace.Create()

' Opening the Hello World project.
Dim project = workspace.OpenProjectAsync(projectPath).Result

' Getting the compilation.
Dim compilation = project.GetCompilationAsync().Result

For Each tree In compilation.SyntaxTrees

    Console.WriteLine(tree.FilePath)

    Dim rootSyntaxNode = tree.GetRootAsync().Result

    For Each node In rootSyntaxNode.DescendantNodes()

        Console.WriteLine($" *** {node.Kind()}")
        Console.WriteLine($"     {node}")
    Next
Next

Console.ReadKey()

This will print all the files and all the syntax nodes in your Hello World project.

Parse source code from text in C#

var syntaxTree = CSharpSyntaxTree.ParseText(
@"using System;
using System.Collections;
using System.Linq;
using System.Text;

namespace HelloWorldApplication
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine(""Hello World"");
}
}
}");

var root = syntaxTree.GetRoot() as CompilationUnitSyntax;

var namespaceSyntax = root.Members.OfType<NamespaceDeclarationSyntax>().First();
        
var programClassSyntax = namespaceSyntax.Members.OfType<ClassDeclarationSyntax>().First();

var mainMethodSyntax = programClassSyntax.Members.OfType<MethodDeclarationSyntax>().First();

Console.WriteLine(mainMethodSyntax.ToString());

Console.ReadKey();

This example will print the Main method from the text analyzing the syntax.

Get the type of ‘var’

To get the actual type for a variable declared using var, call GetSymbolInfo() on the SemanticModel. You can open an existing solution using MSBuildWorkspace, then enumerate its projects and their documents. Use a document to obtain its SyntaxRoot and SemanticModel, then look for VariableDeclarations and retrieve the symbols for the Type of a declared variable like this:

var workspace = MSBuildWorkspace.Create();
var solution = workspace.OpenSolutionAsync("c:\\path\\to\\solution.sln").Result;

foreach (var document in solution.Projects.SelectMany(project => project.Documents))
{
    var rootNode = document.GetSyntaxRootAsync().Result;
    var semanticModel = document.GetSemanticModelAsync().Result;

    var variableDeclarations = rootNode
            .DescendantNodes()
            .OfType<LocalDeclarationStatementSyntax>();
    foreach (var varDeclaration in variableDeclarations)
    {
        var symbolInfo = semanticModel.GetSymbolInfo(varDeclaration.Declaration.Type);
        var typeSymbol = symbolInfo.Symbol; // the type symbol for the variable..
    }
}