Linq的Set操作

Distinct

下图演示 Enumerable.Distinct 方法对字符序列的行为。返回的序列包含输入序列的唯一元素。

Except

下图演示 Enumerable.Except 的行为。返回的序列只包含位于第一个输入序列但不位于第二个输入序列的元素。

Intersect

下图演示 Enumerable.Intersect 的行为。返回的序列包含两个输入序列共有的元素。

Union

下图演示对两个字符序列执行的联合操作。返回的序列包含两个输入序列的唯一的元素。

1. ?#region?Set?Operator
3. ????????/*?The?Distinct原型
4. ?????????*?
5. ?????????*?功能：去掉重复的元素
6. ?????????*?与SqlServer中Distinct关键字一样
7. ?????????*?
8. ?????????*???public?static?IEnumerable<T>?Distinct<T>(
9. ?????????*???this?IEnumerable<T>?source);
10. ?????????*??
11. ?????????*/
12. ????????static?void?DistinctOperatorPrototype()
13. ????????{
14. ????????????string[]?presidents?=?{?"Adams",?"Arthur",?"Buchanan",?"Bush",?"Carter",?"Cleveland"?};
16. ????????????Console.WriteLine("presidents?Count:"+presidents.Count());
17. ????????????IEnumerable<string>?doublePresidents?=?presidents.Concat(presidents);
18. ????????????Console.WriteLine("?after?Concat?presidents?Count:"?+?doublePresidents.Count());
20. ????????????IEnumerable<string>?DistinctPresidents?=?doublePresidents.Distinct();
21. ????????????Console.WriteLine("after?Distinct?presidents?Count:"?+?DistinctPresidents.Count());
22. ????????}
24. ????????/*The?Union原型
25. ?????????*?
26. ?????????*?功能：将多个集合运算成一个集合,消除重复项
27. ?????????*?和SqlServer中关键字Union关键字一样.
28. ?????????*?
29. ?????????*?public?static?IEnumerable<T>?Union<T>(
30. ?????????*????this?IEnumerable<T>?first,
31. ?????????*????IEnumerable<T>?second);
32. ?????????*??
33. ?????????*/
34. ????????static?void?UnionPrototype()
35. ????????{
36. ????????????string[]?presidents?=?{?"Adams",?"Cleveland"?};
38. ????????????Console.WriteLine("presidents?element?count:{0}",?presidents.Count());
40. ????????????IEnumerable<string>?first?=?presidents.Take(4);//取前4个元素
41. ????????????IEnumerable<string>?second?=?presidents.Skip(2);//去掉前2个元素
44. ????????????Console.WriteLine("first?elements?count:{0}",?first.Count());
45. ????????????Console.WriteLine("second?elements?count:{0}",?second.Count());
47. ????????????IEnumerable<string>?concat?=?first.Concat(second);
48. ????????????IEnumerable<string>?union?=?first.Union(second);
50. ?????????
51. ????????????Console.WriteLine("after?concat?element?count:{0}",?concat.Count());
52. ????????????Console.WriteLine("after?union?element?count:{0}",?union.Count());
55. ????????}
57. ????????/*Intersect?原型
58. ?????????*?
59. ?????????*?功能：取2个集合的交集
60. ?????????*?
61. ?????????*?public?static?IEnumerable<T>?Intersect<T>(
62. ?????????*???this?IEnumerable<T>?first,
63. ?????????*???IEnumerable<T>?second);
64. ?????????*
65. ?????????*/
66. ????????static?void?IntersectPrototype()
67. ????????{
68. ????????????string[]?presidents?=?{?"Adams",?second.Count());
70. ????????????IEnumerable<string>?concat?=?first.Concat(second);
71. ????????????IEnumerable<string>?intersect?=?first.Intersect(second);
73. ????????????Console.WriteLine("after?concat?element?count:{0}",?concat.Count());
74. ????????????Console.WriteLine("after?intersect?element?count:{0}",?intersect.Count());
75. ????????}
77. ????????/*Except原型
78. ?????????*?
79. ?????????*?功能：返回的序列只包含位于第一个输入序列但不位于第二个输入序列的元素
80. ?????????*?
81. ?????????*?public?static?IEnumerable<T>?Except<T>(
82. ?????????*???this?IEnumerable<T>?first,
83. ?????????*???IEnumerable<T>?second);
84. ?????????*?
85. ?????????*?
86. ?????????*?
87. ?????????*/
88. ????????static?void?ExceptPrototype()
89. ????????{
90. ????????????string[]?presidents?=?{?"Adams",?"Cleveland"?};
91. ????????????Console.WriteLine("presidents?element?count:{0}",?presidents.Count());
92. ????????????IEnumerable<string>?first?=?presidents.Take(4);//取前4个元素
94. ????????????Console.WriteLine("first?elements?count:{0}",?first.Count());
95. ????????????IEnumerable<string>?except?=?presidents.Except(first);
96. ????????????Console.WriteLine("after?except?element?count:{0}",?except.Count());
98. ????????????foreach?(string?item?in?except)
99. ????????????{
100. ????????????????Console.WriteLine(item);
101. ????????????}
103. ????????}
104. ????????#endregion

（编辑：李大同）

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