Modifying an expression tree | C# Online Compiler

Modifying an expression tree by Krzysztof Polkowski

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Linq.Expressions;

namespace LISTING_2_59_Modifying_an_expression_tree
{

public class MultiplyToAdd : ExpressionVisitor
{
    public Expression Modify(Expression expression)
    {
        return Visit(expression);
    }

    protected override Expression VisitBinary(BinaryExpression b)
    {
        if (b.NodeType == ExpressionType.Multiply)
        {
            Expression left = this.Visit(b.Left);
            Expression right = this.Visit(b.Right);

            // Make this binary expression an Add rather than a multiply operation.  
            return Expression.Add(left, right);
        }

        return base.VisitBinary(b);
    }
}

    public class Program
    {
        public static void Main(string[] args)
        {
            // build the expression tree: Expression<Func<int,int>> square = num => num * num;

            // The parameter for the expression is an integer
            ParameterExpression numParam = Expression.Parameter(typeof(int), "num");

            // The opertion to be performed is to square the parameter
            BinaryExpression squareOperation = Expression.Multiply(numParam, numParam);

            // This creates an expression tree that describes the square operation
            Expression<Func<int, int>> square =
                Expression.Lambda<Func<int, int>>(
                    squareOperation,
                    new ParameterExpression[] { numParam });

            // Compile the tree to make an executable method and assign it to a delegate
            Func<int, int> doSquare = square.Compile();

            // Call the delegate
            Console.WriteLine("Square of 4: {0}", doSquare(4));

            // Modify the expression to replace the multiply with an add

            MultiplyToAdd m = new MultiplyToAdd();

            Expression<Func<int, int>> addExpression = (Expression<Func<int, int>>)m.Modify(square);
            Func<int, int> doAdd = addExpression.Compile();

            Console.WriteLine("Double of 4: {0}", doAdd(4));
        }
    }
}

​x
 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Linq.Expressions;
​
namespace LISTING_2_59_Modifying_an_expression_tree
{
​
public class MultiplyToAdd : ExpressionVisitor
{
    public Expression Modify(Expression expression)
    {
        return Visit(expression);
    }
​
    protected override Expression VisitBinary(BinaryExpression b)
    {
        if (b.NodeType == ExpressionType.Multiply)
        {
            Expression left = this.Visit(b.Left);
            Expression right = this.Visit(b.Right);
​
            // Make this binary expression an Add rather than a multiply operation.  
            return Expression.Add(left, right);
        }
​
        return base.VisitBinary(b);
    }
}
​
    public class Program
    {
        public static void Main(string[] args)
        {
            // build the expression tree: Expression<Func<int,int>> square = num => num * num;
​
            // The parameter for the expression is an integer
            ParameterExpression numParam = Expression.Parameter(typeof(int), "num");
​
            // The opertion to be performed is to square the parameter
            BinaryExpression squareOperation = Expression.Multiply(numParam, numParam);
​
            // This creates an expression tree that describes the square operation
            Expression<Func<int, int>> square =
                Expression.Lambda<Func<int, int>>(
                    squareOperation,
                    new ParameterExpression[] { numParam });
​
            // Compile the tree to make an executable method and assign it to a delegate
            Func<int, int> doSquare = square.Compile();
​
            // Call the delegate
            Console.WriteLine("Square of 4: {0}", doSquare(4));
​
            // Modify the expression to replace the multiply with an add
​
            MultiplyToAdd m = new MultiplyToAdd();
​
            Expression<Func<int, int>> addExpression = (Expression<Func<int, int>>)m.Modify(square);
            Func<int, int> doAdd = addExpression.Compile();
​
            Console.WriteLine("Double of 4: {0}", doAdd(4));
        }
    }
}

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Last Run:	7:09:52 pm
Compile:	0s
Execute:	0.11s
Memory:	0b
CPU:	0s

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