将不确定变为确定~表达式树是否可以有个集合，条件过滤有了新方向续（新增了OR和AND查询）

 1     /// <summary>
 2     /// 条件建立者
 3     /// [单元表达式主要考用用在数据库字段或是其他集合字段中考用直接返回bool查询的]
 4     /// [考用考虑，如果一个内存集合中，考用定义一个属性，属性中有逻辑，例如：return str.Lenght==1;这样的可以用到单元运算符。]
 5     /// </summary>
 6     public static class PredicateBuilder
 7     {
 8         /// <summary>
 9         /// 单元 true 表达式
10         /// </summary>
11         /// <typeparam name="T">指定泛型 T</typeparam>
12         /// <returns>true</returns>
13         public static Expression<Func<T, bool>> True<T>()
14         {
15             return item => true;
16         }
17 
18         /// <summary>
19         /// 单元 false 表达式
20         /// </summary>
21         /// <typeparam name="T">指定泛型 T</typeparam>
22         /// <returns>false</returns>
23         public static Expression<Func<T, bool>> False<T>()
24         {
25             return item => false;
26         }
27 
28         /// <summary>
29         /// 双元 Or 表达式
30         /// </summary>
31         /// <typeparam name="T">指定泛型 T</typeparam>
32         /// <param name="exprleft">左表达式</param>
33         /// <param name="exprright">右表达式</param>
34         /// <returns>返回合并表达式</returns>
35         public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> exprleft, Expression<Func<T, bool>> exprright)
36         {
37             var invokedExpr = Expression.Invoke(exprright, exprleft.Parameters.Cast<Expression>());
38             return Expression.Lambda<Func<T, bool>>(Expression.Or(exprleft.Body, invokedExpr), exprleft.Parameters);
39         }
40 
41         /// <summary>
42         /// 双元 And 表达式
43         /// </summary>
44         /// <typeparam name="T">指定泛型 T</typeparam>
45         /// <param name="exprleft">左表达式</param>
46         /// <param name="exprright">右表达式</param>
47         /// <returns>返回合并表达式</returns>
48         public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> exprleft, Expression<Func<T, bool>> exprright)
49         {
50             var invokedExpr = Expression.Invoke(exprright, exprleft.Parameters.Cast<Expression>());
51             return Expression.Lambda<Func<T, bool>>(Expression.AndAlso(exprleft.Body, invokedExpr), exprleft.Parameters);
52         }
53     }

 1     /// <summary>
 2     /// 功能：条件过滤类
 3     /// 作者：张占岭
 4     /// 日期：2012-6-7
 5     /// </summary>
 6     public class PredicateList<TEntity> : IEnumerable<Expression<Func<TEntity, bool>>> where TEntity : class
 7     {
 8         List<Expression<Func<TEntity, bool>>> expressionList;
 9         public PredicateList()
10         {
11             expressionList = new List<Expression<Func<TEntity, bool>>>();
12         }
13         /// <summary>
14         /// 添加到集合
15         /// </summary>
16         /// <param name="predicate"></param>
17         public void Add(Expression<Func<TEntity, bool>> predicate)
18         {
19             expressionList.Add(predicate);
20         }
21         /// <summary>
22         /// Or操作添加到集合
23         /// </summary>
24         /// <param name="exprleft"></param>
25         /// <param name="exprright"></param>
26         public void AddForOr(Expression<Func<TEntity, bool>> exprleft, Expression<Func<TEntity, bool>> exprright)
27         {
28             expressionList.Add(exprleft.Or(exprright));
29         }
30         /// <summary>
31         /// And操作添加到集合
32         /// </summary>
33         /// <param name="exprleft"></param>
34         /// <param name="exprright"></param>
35         public void AddForAnd(Expression<Func<TEntity, bool>> exprleft, Expression<Func<TEntity, bool>> exprright)
36         {
37             expressionList.Add(exprleft.And(exprright));
38         }
39 
40         #region IEnumerable 成员
41 
42         public IEnumerator GetEnumerator()
43         {
44             return expressionList.GetEnumerator();
45         }
46 
47         #endregion
48 
49         #region IEnumerable<Expression<Func<TEntity>>> 成员
50 
51         IEnumerator<Expression<Func<TEntity, bool>>> IEnumerable<Expression<Func<TEntity, bool>>>.GetEnumerator()
52         {
53             return expressionList.GetEnumerator();
54         }
55 
56         #endregion
57     }

1             PredicateList<UserBases> zzl = new PredicateList<UserBases>();
2             Expression<Func<UserBases, bool>> exp_name = i => i.Name.Contains("zzl");
3             Expression<Func<UserBases, bool>> exp_id = i => i.UserID == 1;
4             zzl.AddForOr(exp_name, exp_id);
5             GetModel(zzl).ForEach(i => Console.WriteLine(i.Name));
6             Console.ReadKey();