如何:将 LINQ 查询与正则表达式合并在一起

此示例演示如何使用 Regex 类创建正则表达式以便在文本字符串中进行更复杂的匹配。 使用 LINQ 查询可以方便地对您要用正则表达式搜索的文件进行准确筛选,以及对结果进行加工。

示例

Class LinqRegExVB

    Shared Sub Main()

        ' Root folder to query, along with all subfolders.
        ' Modify this path as necessary so that it accesses your Visual Studio folder.
        Dim startFolder As String = "C:\program files\Microsoft Visual Studio 9.0\"
        ' One of the following paths may be more appropriate on your computer.
        'string startFolder = @"c:\program files (x86)\Microsoft Visual Studio 9.0\";
        'string startFolder = @"c:\program files\Microsoft Visual Studio 10.0\";
        'string startFolder = @"c:\program files (x86)\Microsoft Visual Studio 10.0\";

        ' Take a snapshot of the file system.
        Dim fileList As IEnumerable(Of System.IO.FileInfo) = GetFiles(startFolder)

        ' Create a regular expression to find all things "Visual".
        Dim searchTerm As System.Text.RegularExpressions.Regex = 
            New System.Text.RegularExpressions.Regex("Visual (Basic|C#|C\+\+|J#|SourceSafe|Studio)")

        ' Search the contents of each .htm file.
        ' Remove the where clause to find even more matches!
        ' This query produces a list of files where a match
        ' was found, and a list of the matches in that file.
        ' Note: Explicit typing of "Match" in select clause.
        ' This is required because MatchCollection is not a 
        ' generic IEnumerable collection.
        Dim queryMatchingFiles = From afile In fileList
                                Where afile.Extension = ".htm"
                                Let fileText = System.IO.File.ReadAllText(afile.FullName)
                                Let matches = searchTerm.Matches(fileText)
                                Where (matches.Count > 0)
                                Select Name = afile.FullName,
                                       Matches = From match As System.Text.RegularExpressions.Match In matches
                                                 Select match.Value

        ' Execute the query.
        Console.WriteLine("The term " & searchTerm.ToString() & " was found in:")

        For Each fileMatches In queryMatchingFiles
            ' Trim the path a bit, then write 
            ' the file name in which a match was found.
            Dim s = fileMatches.Name.Substring(startFolder.Length - 1)
            Console.WriteLine(s)

            ' For this file, write out all the matching strings
            For Each match In fileMatches.Matches
                Console.WriteLine("  " + match)
            Next
        Next

        ' Keep the console window open in debug mode
        Console.WriteLine("Press any key to exit")
        Console.ReadKey()
    End Sub

    ' Function to retrieve a list of files. Note that this is a copy
    ' of the file information.
    Shared Function GetFiles(ByVal root As String) As IEnumerable(Of System.IO.FileInfo)
        Return From file In My.Computer.FileSystem.GetFiles(
                   root, FileIO.SearchOption.SearchAllSubDirectories, "*.*") 
               Select New System.IO.FileInfo(file)
    End Function

End Class
class QueryWithRegEx
{
    public static void Main()
    {
        // Modify this path as necessary so that it accesses your version of Visual Studio.
        string startFolder = @"c:\program files\Microsoft Visual Studio 9.0\";
        // One of the following paths may be more appropriate on your computer.
        //string startFolder = @"c:\program files (x86)\Microsoft Visual Studio 9.0\";
        //string startFolder = @"c:\program files\Microsoft Visual Studio 10.0\";
        //string startFolder = @"c:\program files (x86)\Microsoft Visual Studio 10.0\";

        // Take a snapshot of the file system.
        IEnumerable<System.IO.FileInfo> fileList = GetFiles(startFolder);

        // Create the regular expression to find all things "Visual".
        System.Text.RegularExpressions.Regex searchTerm =
            new System.Text.RegularExpressions.Regex(@"Visual (Basic|C#|C\+\+|J#|SourceSafe|Studio)");

        // Search the contents of each .htm file.
        // Remove the where clause to find even more matchedValues!
        // This query produces a list of files where a match
        // was found, and a list of the matchedValues in that file.
        // Note: Explicit typing of "Match" in select clause.
        // This is required because MatchCollection is not a 
        // generic IEnumerable collection.
        var queryMatchingFiles =
            from file in fileList
            where file.Extension == ".htm"
            let fileText = System.IO.File.ReadAllText(file.FullName)
            let matches = searchTerm.Matches(fileText)
            where matches.Count > 0
            select new
            {
                name = file.FullName,
                matchedValues = from System.Text.RegularExpressions.Match match in matches
                                select match.Value
            };

        // Execute the query.
        Console.WriteLine("The term \"{0}\" was found in:", searchTerm.ToString());

        foreach (var v in queryMatchingFiles)
        {
            // Trim the path a bit, then write 
            // the file name in which a match was found.
            string s = v.name.Substring(startFolder.Length - 1);
            Console.WriteLine(s);

            // For this file, write out all the matching strings
            foreach (var v2 in v.matchedValues)
            {
                Console.WriteLine("  " + v2);
            }
        }

        // Keep the console window open in debug mode
        Console.WriteLine("Press any key to exit");
        Console.ReadKey();
    }

    // This method assumes that the application has discovery 
    // permissions for all folders under the specified path.
    static IEnumerable<System.IO.FileInfo> GetFiles(string path)
    {
        if (!System.IO.Directory.Exists(path))
            throw new System.IO.DirectoryNotFoundException();

        string[] fileNames = null;
        List<System.IO.FileInfo> files = new List<System.IO.FileInfo>();

        fileNames = System.IO.Directory.GetFiles(path, "*.*", System.IO.SearchOption.AllDirectories);
        foreach (string name in fileNames)
        {
            files.Add(new System.IO.FileInfo(name));
        }
        return files;
    }
}

请注意,您还可以查询由 RegEx 搜索返回的 MatchCollection 对象。 在此示例中,结果中仅生成每个匹配项的值。 但也可使用 LINQ 对该集合执行各种筛选、排序和分组操作。 由于 MatchCollection 是非泛型 IEnumerable 集合,因此必须显式声明查询中的范围变量的类型。

编译代码

  • 创建一个面向 .NET Framework 3.5 版的 Visual Studio 项目。 默认情况下,该项目具有对 System.Core.dll 的引用以及针对 System.Linq 命名空间的 using 指令 (C#) 或 Imports 语句 (Visual Basic)。 在 C# 项目中,添加 System.IO 命名空间的 using 指令。

  • 将此代码复制到您的项目。

  • 按 F5 编译并运行程序。

  • 按任意键退出控制台窗口。

请参见

任务

如何:从 CSV 文件生成 XML

概念

LINQ 和字符串

LINQ 和文件目录