Linq Expression 值得注意

研究linq 表达式的时候，遇到一篇不错的博客linq to sql,但是里边中有个知识点就是linq 拼接，最后认真分析才发现其中的Linq引用地方是内存地址，具体代码我粘贴如下：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Linq.Expressions;namespace LinqToString{    public static class PredicateBuilder    {        /*lambel表达式中的True*/        public static Expression<Func<T, bool>> True<T>() {return f=>true; }        /*lambel表达式中的False*/        public static Expression<Func<T,bool>> False<T>(){return f=>false;}        /*lambel表达式中的OR*/        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);        }        /*lambel表达式中的And*/        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);        }        /*Expression<TDelegate>         以表达式树的形式将强类型 lambda 表达式表示为数据结构。此类不能被继承。          * Body表示表达式树的内容，Parameters表示表达式内的参数，ReturnType表示获取 lambda 表达式的返回类型。          */    }   public class LinqMyCondition    {               IList<Student> strudents=new List<Student>                            {                             new Student(1,"j1",21,1),                            new Student(2,"j2",26,3),                            new Student(3,"j3",21,1),                            new Student(4,"j4",27,4),                            new Student(5,"j5",21,1),                             new Student(6,"j6",21,2),                            new Student(7,"j2",21,2)                            };                public List<Student> GetStudentByOR(params string[] keywords)        {            IQueryable<Student> Istus = strudents.AsQueryable();            var predicate = PredicateBuilder.False<Student>();            foreach (string keyword in keywords)            {                string temp = keyword;//这个地方值得注意，确实注意引用地址                predicate = predicate.Or(p => p.sname.Contains(temp));            }            var query=Istus.Where(predicate).ToList();            return query;        }        public List<Student> ShowData(params string[] keywords)        {            IQueryable<Student> IQStudent = strudents.AsQueryable();            var predicat = PredicateBuilder.True<Student>();           // string temp = "";            foreach (string keyword in keywords)            {                string temp = keyword;                predicat = predicat.And(p => p.sname.Contains(temp));                //predicat = predicat.And(p => p.sname.Contains("1"));                //predicat = predicat.And(p => p.gid == 1);            }            var query = IQStudent.Where(predicat).ToList();            return query;        }    }}