C# Language Tutorial => Examining the Structure of an Expression...

Example

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();
visitor.Visit(isBig);

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