C# Language Examining the Structure of an Expression using Visitor


Define a new visitor class by overriding some of the methods of ExpressionVisitor:

class PrintingVisitor : ExpressionVisitor {
    protected override Expression VisitConstant(ConstantExpression node) {
        Console.WriteLine("Constant: {0}", node);
        return base.VisitConstant(node);
    protected override Expression VisitParameter(ParameterExpression node) {
        Console.WriteLine("Parameter: {0}", node);
        return base.VisitParameter(node);
    protected override Expression VisitBinary(BinaryExpression node) {
        Console.WriteLine("Binary with operator {0}", node.NodeType);
        return base.VisitBinary(node);

Call Visit to use this visitor on an existing expression:

Expression<Func<int,bool>> isBig = a => a > 1000000;
var visitor = new PrintingVisitor();