如何查询文件夹中文本文件的内容 (LINQ) (C#)

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 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.  
        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;  
    }  
}