Roslyn Scripting Data Flow Analysis

The DataFlowAnalysis class provides information about how data flows into and out of a region. You can also use it to inspect how variables are read and written within a given block of code.

The DataFlowAnalysis class exposes different properties about unsafe addresses, local variables captured, and much more.

Let's consider the following sample source code containing variable declaration before the for loop and also inside the for loop.

static void DataFlowAnalysisExample()
{
    var tree = CSharpSyntaxTree.ParseText(@"
        public class MyClass
        {
           public void TestMethod()
           {
                int[] outerArray = new int[10] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
                for (int index = 0; index < 10; index++)
                {
                     int[] innerArray = new int[10] { 0, 2, 4, 6, 8, 10, 12, 14, 16, 18 };
                     index = index + 2;
                     outerArray[index – 1] = 5;
                }
           }
        }");

    var Mscorlib = MetadataReference.CreateFromFile(typeof(object).Assembly.Location);

    var compilation = CSharpCompilation.Create("MyCompilation",
        syntaxTrees: new List<SyntaxTree>() { tree }, references: new[] { Mscorlib });
    var model = compilation.GetSemanticModel(tree);

    var forStatement = tree.GetRoot().DescendantNodes().OfType<ForStatementSyntax>().Single();
    DataFlowAnalysis result = model.AnalyzeDataFlow(forStatement);

    foreach (var variable in result.VariablesDeclared)
    {
        Console.WriteLine(variable.Name);
    }            
}

Let's execute the above code, and you will see the local variables defined inside the for loop as an output.

index
innerArray