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HOW TO:使用群組將一個檔案分割成許多檔案 (LINQ)

更新:2007 年 11 月

這個範例顯示的方法可以合併兩個檔案的內容,然後建立一組以新方法組織資料的新檔案。

若要建立資料檔

  1. 將下列名稱複製至 names1.txt 文字檔,並將檔案儲存在方案資料夾中:

    Bankov, Peter
    Holm, Michael
    Garcia, Hugo
    Potra, Cristina
    Noriega, Fabricio
    Aw, Kam Foo
    Beebe, Ann
    Toyoshima, Tim
    Guy, Wey Yuan
    Garcia, Debra
    
  2. 將下列名稱複製至 names2.txt 文字檔,並將檔案儲存在方案資料夾中。請注意,這兩個檔案中有些名稱是相同的。

    Liu, Jinghao
    Bankov, Peter
    Holm, Michael
    Garcia, Hugo
    Beebe, Ann
    Gilchrist, Beth
    Myrcha, Jacek
    Giakoumakis, Leo
    McLin, Nkenge
    El Yassir, Mehdi
    

範例

Class SplitWithGroups

    Shared Sub Main()

        Dim fileA As String() = System.IO.File.ReadAllLines("../../../names1.txt")
        Dim fileB As String() = System.IO.File.ReadAllLines("../../../names2.txt")

        ' Concatenate and remove duplicate names based on
        Dim mergeQuery As IEnumerable(Of String) = fileA.Union(fileB)

        ' Group the names by the first letter in the last name
        Dim groupQuery = From name In mergeQuery _
                     Let n = name.Split(New Char() {","}) _
                     Order By n(0) _
                     Group By groupKey = n(0)(0) _
                     Into groupName = Group

        ' Create a new file for each group that was created
        ' Note that nested foreach loops are required to access
        ' individual items with each group.
        For Each gGroup In groupQuery
            Dim fileName As String = "..'..'..'testFile_" & gGroup.groupKey & ".txt"
            Dim sw As New System.IO.StreamWriter(fileName)
            Console.WriteLine(gGroup.groupKey)
            For Each item In gGroup.groupName
                Console.WriteLine("   " & item.name)
                sw.WriteLine(item.name)
            Next
            sw.Close()
        Next

        ' Keep console window open in debug mode.
        Console.WriteLine("Files have been written. Press any key to exit.")
        Console.ReadKey()

    End Sub
End Class
' Console Output:
' A
'    Aw, Kam Foo
' B
'    Bankov, Peter
'    Beebe, Ann
' E
'    El Yassir, Mehdi
' G
'    Garcia, Hugo
'    Garcia, Debra
'    Giakoumakis, Leo
'    Gilchrist, Beth
'    Guy, Wey Yuan
' H
'    Holm, Michael
' L
'    Liu, Jinghao
' M
'    McLin, Nkenge
'    Myrcha, Jacek
' N
'    Noriega, Fabricio
' P
'    Potra, Cristina
' T
'    Toyoshima, Tim
class SplitWithGroups
{
    static void Main()
    {
        string[] fileA = System.IO.File.ReadAllLines(@"../../../names1.txt");
        string[] fileB = System.IO.File.ReadAllLines(@"../../../names2.txt");

        // Concatenate and remove duplicate names based on
        // default string comparer
        var mergeQuery = fileA.Union(fileB);

        // Group the names by the first letter in the last name.
        var groupQuery = from name in mergeQuery
                         let n = name.Split(',')
                         group name by n[0][0] into g
                         orderby g.Key
                         select g;

        // Create a new file for each group that was created
        // Note that nested foreach loops are required to access
        // individual items with each group.
        foreach (var g in groupQuery)
        {
            // Create the new file name.
            string fileName = @"../../../testFile_" + g.Key + ".txt";

            // Output to display.
            Console.WriteLine(g.Key);

            // Write file.
            using (System.IO.StreamWriter sw = new System.IO.StreamWriter(fileName))
            {
                foreach (var item in g)
                {
                    sw.WriteLine(item);
                    // Output to console for example purposes.
                    Console.WriteLine("   {0}", item);
                }
            }
        }
        // Keep console window open in debug mode.
        Console.WriteLine("Files have been written. Press any key to exit");
        Console.ReadKey();
    }
}
/* Output: 
    A
       Aw, Kam Foo
    B
       Bankov, Peter
       Beebe, Ann
    E
       El Yassir, Mehdi
    G
       Garcia, Hugo
       Guy, Wey Yuan
       Garcia, Debra
       Gilchrist, Beth
       Giakoumakis, Leo
    H
       Holm, Michael
    L
       Liu, Jinghao
    M
       Myrcha, Jacek
       McLin, Nkenge
    N
       Noriega, Fabricio
    P
       Potra, Cristina
    T
       Toyoshima, Tim
 */

程式會在資料檔的資料夾中寫入每個群組的個別檔案。

編譯程式碼

  • 建立以 .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)。在 C# 專案中,請加入 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。

請參閱

概念

LINQ 和字串

LINQ 和檔案目錄