如何在目录树中查询重复文件 (LINQ) (C#)
有时，具有相同名称的文件可能位于多个文件夹中。 例如，在 Visual Studio 安装文件夹下，多个文件夹中都有 readme.htm 文件。 此示例显示如何在指定根文件夹下查询此类重复文件名。 第二个示例显示如何查询大小和上次写入时间都匹配的文件。
示例
class QueryDuplicateFileNames
{
static void Main(string[] args)
{
// Uncomment QueryDuplicates2 to run that query.
QueryDuplicates();
// QueryDuplicates2();
// Keep the console window open in debug mode.
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
}
static void QueryDuplicates()
{
// Change the root drive or folder if 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);
// used in WriteLine to keep the lines shorter
int charsToSkip = startFolder.Length;
// var can be used for convenience with groups.
var queryDupNames =
from file in fileList
group file.FullName.Substring(charsToSkip) by file.Name into fileGroup
where fileGroup.Count() > 1
select fileGroup;
// Pass the query to a method that will
// output one page at a time.
PageOutput<string, string>(queryDupNames);
}
// A Group key that can be passed to a separate method.
// Override Equals and GetHashCode to define equality for the key.
// Override ToString to provide a friendly name for Key.ToString()
class PortableKey
{
public string Name { get; set; }
public DateTime LastWriteTime { get; set; }
public long Length { get; set; }
public override bool Equals(object obj)
{
PortableKey other = (PortableKey)obj;
return other.LastWriteTime == this.LastWriteTime &&
other.Length == this.Length &&
other.Name == this.Name;
}
public override int GetHashCode()
{
string str = $"{this.LastWriteTime}{this.Length}{this.Name}";
return str.GetHashCode();
}
public override string ToString()
{
return $"{this.Name} {this.Length} {this.LastWriteTime}";
}
}
static void QueryDuplicates2()
{
// Change the root drive or folder if necessary.
string startFolder = @"c:\program files\Microsoft Visual Studio 9.0\Common7";
// Make the lines shorter for the console display
int charsToSkip = startFolder.Length;
// Take a snapshot of the file system.
System.IO.DirectoryInfo dir = new System.IO.DirectoryInfo(startFolder);
IEnumerable<System.IO.FileInfo> fileList = dir.GetFiles("*.*", System.IO.SearchOption.AllDirectories);
// Note the use of a compound key. Files that match
// all three properties belong to the same group.
// A named type is used to enable the query to be
// passed to another method. Anonymous types can also be used
// for composite keys but cannot be passed across method boundaries
//
var queryDupFiles =
from file in fileList
group file.FullName.Substring(charsToSkip) by
new PortableKey { Name = file.Name, LastWriteTime = file.LastWriteTime, Length = file.Length } into fileGroup
where fileGroup.Count() > 1
select fileGroup;
var list = queryDupFiles.ToList();
int i = queryDupFiles.Count();
PageOutput<PortableKey, string>(queryDupFiles);
}
// A generic method to page the output of the QueryDuplications methods
// Here the type of the group must be specified explicitly. "var" cannot
// be used in method signatures. This method does not display more than one
// group per page.
private static void PageOutput<K, V>(IEnumerable<System.Linq.IGrouping<K, V>> groupByExtList)
{
// Flag to break out of paging loop.
bool goAgain = true;
// "3" = 1 line for extension + 1 for "Press any key" + 1 for input cursor.
int numLines = Console.WindowHeight - 3;
// Iterate through the outer collection of groups.
foreach (var filegroup in groupByExtList)
{
// Start a new extension at the top of a page.
int currentLine = 0;
// Output only as many lines of the current group as will fit in the window.
do
{
Console.Clear();
Console.WriteLine("Filename = {0}", filegroup.Key.ToString() == String.Empty ? "[none]" : filegroup.Key.ToString());
// Get 'numLines' number of items starting at number 'currentLine'.
var resultPage = filegroup.Skip(currentLine).Take(numLines);
//Execute the resultPage query
foreach (var fileName in resultPage)
{
Console.WriteLine("\t{0}", fileName);
}
// Increment the line counter.
currentLine += numLines;
// Give the user a chance to escape.
Console.WriteLine("Press any key to continue or the 'End' key to break...");
ConsoleKey key = Console.ReadKey().Key;
if (key == ConsoleKey.End)
{
goAgain = false;
break;
}
} while (currentLine < filegroup.Count());
if (goAgain == false)
break;
}
}
}
第一个查询使用简单键来确定匹配；此查询可以找到名称相同但内容可能不同的文件。 第二个查询使用复合键来匹配 FileInfo 对象的 3 个属性。 此查询更可能找到名称相同且内容相似或相同的文件。
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。