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【CSharp】比较两个文件夹的内容 (LINQ)

作者:DDT / 发布于2012/10/8/ 657

将自定义比较器类与标准查询运算符一起使用。

<div>using System.IO;
using System.Collections.Generic;
namespace QueryCompareTwoDirs
{
 class CompareDirs
 {</div>
<div> static void Main(string[] args)
 {</div>
<div> // Create two identical or different temporary folders 
 // on a local drive and change these file paths.
 string pathA = @"C:\TestDir";
 string pathB = @"C:\TestDir2";</div>
<div> DirectoryInfo dir1 = new DirectoryInfo(pathA);
 DirectoryInfo dir2 = new DirectoryInfo(pathB);</div>
<div> // Take a snapshot of the file system.
 IEnumerable<FileInfo> list1 = dir1.GetFiles("*.*", SearchOption.AllDirectories);
 IEnumerable<FileInfo> list2 = dir2.GetFiles("*.*", SearchOption.AllDirectories);</div>
<div> //A custom file comparer defined below
 FileCompare myFileCompare = new FileCompare();</div>
<div> // This query determines whether the two folders contain
 // identical file lists, based on the custom file comparer
 // that is defined in the FileCompare class.
 // The query executes immediately because it returns a bool.
 bool areIdentical = list1.SequenceEqual(list2, myFileCompare);</div>
<div> if (areIdentical == true)
 {
 Console.WriteLine("the two folders are the same");
 }
 else
 {
 Console.WriteLine("The two folders are not the same");
 }
<div> // Find the common files. It produces a sequence and doesn't 
 // execute until the foreach statement.
 var queryCommonFiles = list1.Intersect(list2, myFileCompare);</div>
<div> if (queryCommonFiles.Count() > 0)
 {
 Console.WriteLine("The following files are in both folders:");
 foreach (var v in queryCommonFiles)
 {
 Console.WriteLine(v.FullName); //shows which items end up in result list
 }
 }
 else
 {
 Console.WriteLine("There are no common files in the two folders.");
 }
<div> // Find the set difference between the two folders.
 // For this example we only check one way.
 var queryList1Only = (from file in list1
 select file).Except(list2, myFileCompare);</div>
<div> Console.WriteLine("The following files are in list1 but not list2:");
 foreach (var v in queryList1Only)
 {
 Console.WriteLine(v.FullName);
 }
<div> // Keep the console window open in debug mode.
 Console.WriteLine("Press any key to exit.");
 Console.ReadKey();
 }
 }
<div> // This implementation defines a very simple comparison
 // between two FileInfo objects. It only compares the name
 // of the files being compared and their length in bytes.
 class FileCompare : IEqualityComparer<FileInfo>
 {
 public FileCompare() { }
<div> public bool Equals(FileInfo f1, FileInfo f2)
 {
 return (f1.Name == f2.Name &&
 f1.Length == f2.Length);
 }
<div> // Return a hash that reflects the comparison criteria. According to the 
 // rules for IEqualityComparer<T>, if Equals is true, then the hash codes must
 // also be equal. Because equality as defined here is a simple value equality, not
 // reference identity, it is possible that two or more objects will produce the same
 // hash code.
 public int GetHashCode(FileInfo fi)
 {
 string s = String.Format("{0}{1}", fi.Name, fi.Length);
 return s.GetHashCode();
 }
 }
}
</div>

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