如何查询文件夹中文本文件的内容 (LINQ) (C#)
此示例演示如何查询指定目录树中的所有文件、打开每个文件并检查其内容。 此类技术可用于对目录树的内容创建索引或反向索引。 此示例中执行的是简单的字符串搜索。 但是，可使用正则表达式执行类型更复杂的模式匹配。 有关详细信息，请参阅如何将 LINQ 查询与正则表达式合并 (C#)。
示例
class QueryContents
{
public static void Main()
{
// Modify this path as necessary.
string startFolder = @"c:\program files\Microsoft Visual Studio 9.0\";
// Take a snapshot of the file system.
System.IO.DirectoryInfo dir = new System.IO.DirectoryInfo(startFolder);
// This method assumes that the application has discovery permissions
// for all folders under the specified path.
IEnumerable<System.IO.FileInfo> fileList = dir.GetFiles("*.*", System.IO.SearchOption.AllDirectories);
string searchTerm = @"Visual Studio";
// Search the contents of each file.
// A regular expression created with the RegEx class
// could be used instead of the Contains method.
// queryMatchingFiles is an IEnumerable<string>.
var queryMatchingFiles =
from file in fileList
where file.Extension == ".htm"
let fileText = GetFileText(file.FullName)
where fileText.Contains(searchTerm)
select file.FullName;
// Execute the query.
Console.WriteLine("The term \"{0}\" was found in:", searchTerm);
foreach (string filename in queryMatchingFiles)
{
Console.WriteLine(filename);
}
// Keep the console window open in debug mode.
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
// Read the contents of the file.
static string GetFileText(string name)
{
string fileContents = String.Empty;
// If the file has been deleted since we took
// the snapshot, ignore it and return the empty string.
if (System.IO.File.Exists(name))
{
fileContents = System.IO.File.ReadAllText(name);
}
return fileContents;
}
}
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。