HOW TO：查詢包含指定一組字的句子 (LINQ)
這個範例顯示如何在文字檔中尋找含有所指定詞組的句子。 雖然這個範例硬式編碼了搜尋詞彙的陣列，但是這類陣列的內容是可以在執行階段動態填入 (Populate) 的。 在這個範例中，查詢傳回的句子會包含 "Historically"、"data" 和 "integrated" 這些字。
範例
Class FindSentences
Shared Sub Main()
Dim text As String = "Historically, the world of data and the world of objects " &
"have not been well integrated. Programmers work in C# or Visual Basic " &
"and also in SQL or XQuery. On the one side are concepts such as classes, " &
"objects, fields, inheritance, and .NET Framework APIs. On the other side " &
"are tables, columns, rows, nodes, and separate languages for dealing with " &
"them. Data types often require translation between the two worlds; there are " &
"different standard functions. Because the object world has no notion of query, a " &
"query can only be represented as a string without compile-time type checking or " &
"IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to " &
"objects in memory is often tedious and error-prone."
' Split the text block into an array of sentences.
Dim sentences As String() = text.Split(New Char() {".", "?", "!"})
' Define the search terms. This list could also be dynamically populated at runtime
Dim wordsToMatch As String() = {"Historically", "data", "integrated"}
' Find sentences that contain all the terms in the wordsToMatch array
' Note that the number of terms to match is not specified at compile time
Dim sentenceQuery = From sentence In sentences
Let w = sentence.Split(New Char() {" ", ",", ".", ";", ":"},
StringSplitOptions.RemoveEmptyEntries)
Where w.Distinct().Intersect(wordsToMatch).Count = wordsToMatch.Count()
Select sentence
' Execute the query
For Each str As String In sentenceQuery
Console.WriteLine(str)
Next
' Keep console window open in debug mode.
Console.WriteLine("Press any key to exit.")
Console.ReadKey()
End Sub
End Class
' Output:
' Historically, the world of data and the world of objects have not been well integrated
class FindSentences
{
static void Main()
{
string text = @"Historically, the world of data and the world of objects " +
@"have not been well integrated. Programmers work in C# or Visual Basic " +
@"and also in SQL or XQuery. On the one side are concepts such as classes, " +
@"objects, fields, inheritance, and .NET Framework APIs. On the other side " +
@"are tables, columns, rows, nodes, and separate languages for dealing with " +
@"them. Data types often require translation between the two worlds; there are " +
@"different standard functions. Because the object world has no notion of query, a " +
@"query can only be represented as a string without compile-time type checking or " +
@"IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to " +
@"objects in memory is often tedious and error-prone.";
// Split the text block into an array of sentences.
string[] sentences = text.Split(new char[] { '.', '?', '!' });
// Define the search terms. This list could also be dynamically populated at runtime.
string[] wordsToMatch = { "Historically", "data", "integrated" };
// Find sentences that contain all the terms in the wordsToMatch array.
// Note that the number of terms to match is not specified at compile time.
var sentenceQuery = from sentence in sentences
let w = sentence.Split(new char[] { '.', '?', '!', ' ', ';', ':', ',' },
StringSplitOptions.RemoveEmptyEntries)
where w.Distinct().Intersect(wordsToMatch).Count() == wordsToMatch.Count()
select sentence;
// Execute the query. Note that you can explicitly type
// the iteration variable here even though sentenceQuery
// was implicitly typed.
foreach (string str in sentenceQuery)
{
Console.WriteLine(str);
}
// Keep the console window open in debug mode.
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
}
/* Output:
Historically, the world of data and the world of objects have not been well integrated
*/
查詢的運作方式是先將文字分割成句子，然後再將句子分割成保留每個字的字串陣列。 在這些陣列中，Distinct 方法會移除所有重複的字，然後查詢就會對這個文字陣列和 wordstoMatch 陣列執行 Intersect 作業。 如果交集的計數與 wordsToMatch 陣列的計數相同，則所有字都可以在文字中找到，因而傳回原始句子。
在 Split 呼叫中，標點符號會當成分隔符號，以從字串中移除。 例如，如果您不這麼做，則您的字串 "Historically," 會與 wordsToMatch 陣列中的 "Historically" 不符。 根據來源文字中出現的標點符號類型的不同，您可能需要使用其他分隔符號。
編譯程式碼
建立一個以 .NET Framework 3.5 版為目標的 Visual Studio 專案。 專案預設會含 System.Core.dll 的參考，以及 System.Linq 命名空間 (Namespace) 的 using 指示詞 (C#) 或 Imports 陳述式 (Visual Basic)。 請在 C# 專案中，加入 System.IO 命名空間的 using 指示詞。
將此程式碼複製至您的專案。
按 F5 編譯和執行程式。
按任何鍵離開主控台視窗。