這一篇介紹了下面的內容:
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1 using System;
2 using System.Collections.Generic;
3 using System.ComponentModel;
4 using System.Data;
5 using System.Drawing;
6 using System.Linq;
7 using System.Text;
8 using System.Windows.Forms;
9
10 namespace WindowsFormsApplication1
11 {
12 public partial class Form1 : Form
13 {
14 public Form1()
15 {
16 InitializeComponent();
17 }
18
19 private void Form1_Load(object sender, EventArgs e)
20 {
21
22 }
23
24 private void button1_Click(object sender, EventArgs e)
25 {
26 //查詢object數組
27 Object[] array = { "String", 12, true, 'a' };
28 var types = array
29 .Select(s => s.GetType().Name)
30 .OrderBy(s => s);
31 ObjectDumper.Write(types);
32 }
33
34 private void button2_Click(object sender, EventArgs e)
35 {
36 //查詢強類型數組
37 Book[] books ={
38 new Book{Title="Linq in Action"},
39 new Book{Title="Linq for Fun"},
40 new Book{Title="Extreme LINQ"}
41 };
42
43 var titles =
44 books
45 .Where(s => s.Title.Contains("Action"))
46 .Select(s => s.Title);
47
48 ObjectDumper.Write(titles);
49 }
50
51 private void button3_Click(object sender, EventArgs e)
52 {
53 //查詢泛型字典
54 var dic = new Dictionary<int, string>();
55 dic.Add(0, "zero");
56 dic.Add(1, "un");
57 dic.Add(2, "deux");
58 dic.Add(3, "trois");
59 dic.Add(4, "quatre");
60 var list =
61 dic
62 .Where(s => s.Key % 2 == 0)
63 .Select(s => s.Value);
64
65 ObjectDumper.Write(list);
66 }
67
68 private void button4_Click(object sender, EventArgs e)
69 {
70 //查詢字符串, 字符串實現了IEnumerable<Char>接口
71 var count = "Non-letter characters in this string: 6"
72 .Where(s => !Char.IsLetter(s))
73 .Count();
74
75 ObjectDumper.Write(count);
76 }
77
78 private void button5_Click(object sender, EventArgs e)
79 {
80 string[] books ={"Funny Stories","All your base are belong to us",
81 "LINQ rules","C# on Rails","Bonjour mon Amour"};
82 var query =
83 books
84 .Where(s => s.Length > 10)
85 .Select(s => new { Book = s.ToUpper() });
86
87 var query1 =
88 from s in books
89 where s.Length > 10
90 orderby s
91 select new { Book = s.ToUpper() };
92
93 dataGridView1.DataSource = query1.ToList();
94 }
95
96 private void button6_Click(object sender, EventArgs e)
97 {
98 var query =
99 from s in SampleData.Books
100 where s.Title.Length > 5
101 orderby s.Title
102 select new { Book = s.Title, Price = s.Price };
103
104 dataGridView2.DataSource = query.ToList();
105 }
106
107 private void button7_Click(object sender, EventArgs e)
108 {
109 //SelectMany
110
111 var query1 =
112 SampleData.Books
113 .SelectMany(s => s.Authors);
114 ObjectDumper.Write(query1);
115
116 var query =
117 from book in SampleData.Books
118 from author in book.Authors
119 select author.FirstName + author.LastName;
120
121 ObjectDumper.Write(query);
122 }
123
124 private void button8_Click(object sender, EventArgs e)
125 {
126 var book =
127 SampleData.Books
128 .Select((s, no) => new { no, s.Title })
129 .OrderBy(s => s.Title);
130
131 //無法翻譯為等同的查詢表達式語法
132
133 ObjectDumper.Write(book);
134
135 }
136
137 private void button9_Click(object sender, EventArgs e)
138 {
139 //Distinct操作符
140 var query =
141 SampleData.Books
142 .SelectMany(s => s.Authors)
143 .Select(s => s.FirstName + s.LastName);
144 ObjectDumper.Write(query);
145
146 //去除重復的author,C#沒有和distinct等同的查詢表達式
147 var query1 =
148 SampleData.Books
149 .SelectMany(s => s.Authors)
150 .Distinct()
151 .Select(s => s.FirstName + s.LastName);
152 Console.WriteLine();
153 ObjectDumper.Write(query1);
154
155 }
156
157 private void button10_Click(object sender, EventArgs e)
158 {
159 //排序
160 var query =
161 from s in SampleData.Books
162 orderby s.Publisher.Name, s.Price descending, s.Title
163 select new
164 {
165 Publisher=s.Publisher.Name,
166 s.Price,
167 s.Title
168 };
169 dataGridView1.DataSource = query.ToList();
170 ObjectDumper.Write(query);
171
172 var query1 =
173 SampleData.Books
174 .OrderBy(s => s.Publisher.Name)
175 .ThenByDescending(s => s.Price)
176 .ThenBy(s => s.Title)
177 .Select(s => new
178 {
179 publisher = s.Publisher.Name,
180 s.Price,
181 s.Title
182 });
183 Console.WriteLine();
184 ObjectDumper.Write(query1);
185
186 }
187
188 private void button11_Click(object sender, EventArgs e)
189 {
190 //嵌套查詢
191
192 var query =
193 from s in SampleData.Publishers
194 select new
195 {
196 item1 = s.Name,
197 item2 =
198 from book in SampleData.Books
199 where book.Publisher.Name == s.Name
200 select book
201 };
202
203 foreach (var m in query)
204 {
205 Console.WriteLine(m.item1+":");
206 foreach (var k in m.item2)
207 {
208 Console.WriteLine(k.Title);
209 }
210 Console.WriteLine();
211 }
212
213
214 }
215
216 private void button12_Click(object sender, EventArgs e)
217 {
218 //分組
219 //代碼讓圖書按出版社分組.屬於同一出版社的圖書將被分到相同的組中.
220 //在這個查詢中,該分組publisherBooks對象是IGrouping<TKey,T>接口.
221 //其中T為集合IEnumerable<Book>
222
223 var query =
224 from s in SampleData.Books
225 group s by s.Publisher into publisherBooks
226 select new
227 {
228 publisher=publisherBooks.Key.Name,
229 books=publisherBooks,
230 booksum=publisherBooks.Count()
231 };
232 foreach (var m in query)
233 {
234 Console.WriteLine(m.publisher + ":");
235 foreach (var k in m.books)
236 {
237 Console.WriteLine(k.Title);
238 }
239 Console.WriteLine(m.booksum);
240 Console.WriteLine();
241 }
242
243 }
244
245 private void button13_Click(object sender, EventArgs e)
246 {
247 //組連接
248 var query =
249 from s in SampleData.Publishers
250 join book in SampleData.Books
251 on s equals book.Publisher into publisherBooks
252 select new
253 {
254 publisher=s.Name,
255 books=publisherBooks
256 };
257
258 foreach (var m in query)
259 {
260 Console.WriteLine(m.publisher + ":");
261 foreach (var k in m.books)
262 {
263 Console.WriteLine(k.Title);
264 }
265 Console.WriteLine();
266 }
267
268 }
269
270 private void button14_Click(object sender, EventArgs e)
271 {
272 //內連接,旨在找到兩個序列的交集
273 //和組連接的差別是,沒有使用into關鍵字將元素分組,而是將圖書投影在了出版社對象上
274 //注意沒有任何書籍的出版社沒有顯示出來,這是因為在兩個待連接序列中均符合條件的組合才會出現在結果序列中.
275 var query =
276 from s in SampleData.Publishers
277 join book in SampleData.Books on s equals book.Publisher
278 select new
279 {
280 publisher=s.Name,
281 books=book.Title
282 };
283
284 var query2=
285 SampleData.Publishers
286 .Join(SampleData.Books, //內部序列
287 s=>s, //外部的key選擇器
288 book=>book.Publisher, //內部的key選擇器
289 (s,book)=>new //結果選擇器
290 {
291 publisher=s.Name,
292 books=book.Title
293 });
294
295 ObjectDumper.Write(query2);
296
297 foreach (var m in query)
298 {
299 Console.WriteLine(m.publisher + ":");
300 Console.WriteLine(m.books);
301 Console.WriteLine();
302 }
303
304 }
305
306 private void button15_Click(object sender, EventArgs e)
307 {
308 //左外連接
309 var query =
310 from s in SampleData.Publishers
311 join book in SampleData.Books
312 on s equals book.Publisher into publisherBooks
313 from book in publisherBooks.DefaultIfEmpty() //為空序列提供默認元素
314 select new
315 {
316 publisher=s.Name,
317 books=book==default(Book)?"(no books)":book.Title
318 };
319
320 ObjectDumper.Write(query);
321 }
322
323 private void button16_Click(object sender, EventArgs e)
324 {
325 //交叉連接, 計算出兩個序列中所有元素的積
326 //結果序列由一個序列的每個元素和另一個序列中每個元素的完全組合構成
327 var query =
328 from s in SampleData.Publishers
329 from book in SampleData.Books
330 select new
331 {
332 correct=(s==book.Publisher),
333 publisher=s.Name,
334 books=book.Title
335 };
336 ObjectDumper.Write(query);
337 }
338
339 private void button17_Click(object sender, EventArgs e)
340 {
341 //skip,take
342 var list1 = new List<string>();
343 for (int i = 0; i < 100; i++)
344 list1.Add(i.ToString());
345
346 var query =
347 list1
348 .Select(s=>s)
349 .Skip(90).Take(10);
350
351
352 ObjectDumper.Write(query);
353 }
354
355
356
357
358
359 }
360
361
362 }
本節源代碼下載
原創文章,出自"博客園, 豬悟能'S博客" : http://www.cnblogs.com/hackpig/
