How to get the class identifier from object instantiation using Roslyn

Question

I'm trying to create an analyzer that will find where each method invocation comes from especially the class where the method is defined.

let's assume we have the following code:

 Movie myMovie = new Movie();
 myMovie.Rent();

my analyzer till now can return the expression myMovie.Rent() as ExpressionSyntax

What exactly I want, is where the analyzer found a method invocation using an object in this case myMovie.Rent(), returns the class where the method is defined and the object is instantiated in this case is Movie.

I'm blocked that why I didn't write any code for it if you have any idea or code example, I appreciate it.

score 1 · Accepted Answer · answered May 12 '19 at 10:00

First of all, in your analyzer class, inside the Initialize method you should register the syntax node action:

public override void Initialize(AnalysisContext context)
{
    context.RegisterSyntaxNodeAction(SyntaxNodeAnalyze, SyntaxKind.InvocationExpression);
}

In this method, we registered SyntaxNodeAnalyze method to get callbacks from the analyzer. Inside this method, by using the 'SyntaxNodeAnalysisContext' we can query information about the semantic objects. In the following sample, I used SemanticModel to be able to enumerate the custom attributes that I was declared and now, I used them above the method declaration.

private static void SyntaxNodeAnalyze(SyntaxNodeAnalysisContext context)
{
    SemanticModel semanticModel = context.SemanticModel;
    InvocationExpressionSyntax method = (InvocationExpressionSyntax)context.Node;

    var info = semanticModel.GetSymbolInfo(method).Symbol;
    if (info == null)
         return new List<AttributeData>();

    var attribs = info.GetAttributes().Where(f => f.AttributeClass.MetadataName.Equals(typeof(ThrowsExceptionAttribute).Name));

    foreach (var attrib in attribs)
    {
        ...
    }            
}

As you can see in the above code, we can gather useful information by using the GetSymbolInfo method of the 'SemanticModel'. You can use this method to get information about Methods, Properties and other semantic objects.

Hey @Amin thanks for the answer, the problem is that my analyzer doesn't contains an **Initialize** method. and can i know the class that define the object that call a given method from the 'attribs' variable? — Hamza, May 13 '19 at 00:02
The `Initialize` method comes from the `DiagnosticAnalyzer` class. Your class should be inherited from this, then you override the `Initialize` method. — Amin, May 13 '19 at 04:15
You can find it in the following repository on Github : [Checked Exception In C#](https://github.com/AminEsmaeily/Portia.Roslyn.CheckedException) — Amin, May 13 '19 at 05:20

How to get the class identifier from object instantiation using Roslyn

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