將不確定變為確定~表達式樹是否可以有個集合，條件過濾有了新方向續（新增了OR和AND查詢）

 1     /// <summary>
 2     /// 條件建立者
 3     /// [單元表達式主要考用用在數據庫字段或是其他集合字段中考用直接返回bool查詢的]
 4     /// [考用考慮，如果一個內存集合中，考用定義一個屬性，屬性中有邏輯，例如：return str.Lenght==1;這樣的可以用到單元運算符。]
 5     /// </summary>
 6     public static class PredicateBuilder
 7     {
 8         /// <summary>
 9         /// 單元 true 表達式
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         /// 單元 false 表達式
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         /// 雙元 Or 表達式
30         /// </summary>
31         /// <typeparam name="T">指定泛型 T</typeparam>
32         /// <param name="exprleft">左表達式</param>
33         /// <param name="exprright">右表達式</param>
34         /// <returns>返回合并表達式</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         /// 雙元 And 表達式
43         /// </summary>
44         /// <typeparam name="T">指定泛型 T</typeparam>
45         /// <param name="exprleft">左表達式</param>
46         /// <param name="exprright">右表達式</param>
47         /// <returns>返回合并表達式</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：條件過濾類
 3     /// 作者：張占嶺
 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 成員
41 
42         public IEnumerator GetEnumerator()
43         {
44             return expressionList.GetEnumerator();
45         }
46 
47         #endregion
48 
49         #region IEnumerable<Expression<Func<TEntity>>> 成員
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();