Semantic Model

Introduction#

In contrast to the Syntax API the exposes all kinds of syntax level information, the semantic model gives our code more “meaning” and allows us to answer questions like “What names are in scope at this location?”, “What members are accessible from this method?”, “What variables are used in this block of text?”, “What does this name/expression refer to?“.

Remarks#

• Querying the Semantic Model is more costly than querying the Syntax Tree, due to the fact that it most commonly triggers a compilation.

Getting the Semantic Model

There qutie a fiew ways to get the sematic model.

• From a Document class

  Document document = ...;
  SemanticModel semanticModel = await document.GetSemanticModelAsync();

• From a Compilationclass

  CSharpCompilation compilation = ...;
  var semanticModel = await compilation.GetSemanticModel(syntaxTree);

• From an AnalysisContext. Fro example inside a DiagnosticAnalyzer you can do:

  public override void Initialize(AnalysisContext context)
  {
      context.RegisterSemanticModelAction(x =>
      {
          var semanticModel = x.SemanticModel;
          // Do magical magic here.
      });
  }

Get all the references to a method

var syntaxRoot = await document.GetSyntaxRootAsync();

var semanticModel = await document.GetSemanticModelAsync();
var sampleMethodInvocation = syntaxRoot
    .DescendantNodes()
    .OfType<InvocationExpressionSyntax>()
    .First();

var sampleMethodSymbol = semanticModel.GetSymbolInfo(sampleMethodInvocation).Symbol;
var referencesToSampleMethod = await SymbolFinder.FindReferencesAsync(sampleMethodSymbol, document.Project.Solution);