Anding two expressions together

expressionManipulation.cs

using System;
using System.Collections.ObjectModel;
using System.Linq.Expressions;

namespace CTM.Home.MaiyaReports.Processors
{

  void Main()
  {
  	Expression<Func<ArrayList, bool>> @default = r => r.Count > 0 && r.Count < 2;
  	
  	Expression<Func<ArrayList, bool>> extra = ar => ar.Capacity > 0;
  	
  	@default.AndAlso(extra).Dump();
  }
  
  class ParameterVisitor : ExpressionVisitor
  {
  	private readonly ReadOnlyCollection<ParameterExpression> from, to;
  	public ParameterVisitor(
  		ReadOnlyCollection<ParameterExpression> from,
  		ReadOnlyCollection<ParameterExpression> to)
  	{
  		if (from == null) throw new ArgumentNullException("from");
  		if (to == null) throw new ArgumentNullException("to");
  		if (from.Count != to.Count) throw new InvalidOperationException(
  				"Parameter lengths must match");
  		this.from = from;
  		this.to = to;
  	}
  	protected override Expression VisitParameter(ParameterExpression node)
  	{
  		for (int i = 0; i < from.Count; i++)
  		{
  			if (node == from[i]) return to[i];
  		}
  		return node;
  	}
  }
  
  public static class ExpressionExtensions
  {
  	public static Expression<Func<T, bool>> AndAlso<T>(this Expression<Func<T, bool>> x, Expression<Func<T, bool>> y)
  	{
  	var newY = new ParameterVisitor(y.Parameters, x.Parameters)
  		.VisitAndConvert(y.Body, "AndAlso");
  	return Expression.Lambda<Func<T, bool>>(
  		Expression.AndAlso(x.Body, newY),
  		x.Parameters);
  	}
  }
}