using System;using System.Collections.Generic;using System.IO;using System.Linq;using System.Linq.Expressions;using System.Security.Cryptography;using System.Text;namespace Aliexpress.Common.CommonHelper{//public static class PredicateBuilder//{// /// <summary>// /// 机关函数应用True时：单个AND有效，多个AND有效；单个OR无效，多个OR无效；混应时写在AND后的OR有效 // /// </summary>// /// <typeparam name="T"></typeparam>// /// <returns></returns>// public static Expression<Func<T, bool>> True<T>() { return f => true; }// /// <summary>// /// 机关函数应用False时：单个AND无效，多个AND无效；单个OR有效，多个OR有效；混应时写在OR后面的AND有效 // /// </summary>// /// <typeparam name="T"></typeparam>// /// <returns></returns>// public static Expression<Func<T, bool>> False<T>() { return f => false; }// public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1,// Expression<Func<T, bool>> expr2)// {// var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());// return Expression.Lambda<Func<T, bool>>// (Expression.Or(expr1.Body, invokedExpr), expr1.Parameters);// }// public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,// Expression<Func<T, bool>> expr2)// {// var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());// return Expression.Lambda<Func<T, bool>>// (Expression.And(expr1.Body, invokedExpr), expr1.Parameters);// }//} public class ParameterRebinder : ExpressionVisitor{private readonly Dictionary<ParameterExpression, ParameterExpression> map;public ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map){this.map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();}public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map, Expression exp){return new ParameterRebinder(map).Visit(exp);}protected override Expression VisitParameter(ParameterExpression p){ParameterExpression replacement;if (map.TryGetValue(p, out replacement)){p = replacement;}return base.VisitParameter(p);}}  public static class PredicateBuilder{public static Expression<Func<T, bool>> True<T>() { return f => true; }public static Expression<Func<T, bool>> False<T>() { return f => false; }public static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge){// build parameter map (from parameters of second to parameters of first)var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f);// replace parameters in the second lambda expression with parameters from the firstvar secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);// apply composition of lambda expression bodies to parameters from the first expression return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);}public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second){return first.Compose(second, Expression.And);}public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second){return first.Compose(second, Expression.Or);}}}