如何将 LINQ 查询与正则表达式合并 (C#)
此示例演示如何使用 Regex 类在文本字符串中为更复杂的匹配创建正则表达式。 通过 LINQ 查询可以轻松地准确筛选要用正则表达式搜索的文件，并对结果进行改良。
示例
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 (x86)\Microsoft Visual Studio 14.0\";
// One of the following paths may be more appropriate on your computer.
//string startFolder = @"C:\Program Files (x86)\Microsoft Visual Studio\2017\";
// 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\+\+|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，还可以查询 RegEx 搜索返回的 MatchCollection 对象。 在本例中，只在结果中生成每个匹配项的值。 但是，也可以使用 LINQ 对集合执行筛选、排序和分组等各种操作。 由于 MatchCollection 为非泛型 IEnumerable 集合，所以必须显式声明查询中范围变量的类型。
编译代码
使用 System.Linq 和 System.IO 命名空间的 using 指令创建 C# 控制台应用程序项目。