Como: Comparar o Sumário de duas pastas (LINQ)
Este exemplo demonstra três maneiras para comparar duas listagens do arquivo:
Consultando um valor booliano que especifica se as duas listas de arquivo são idênticos.
Consultando a interseção recuperar os arquivos que estão em ambas as pastas.
Consultando a diferença de conjunto recuperar os arquivos que estão em uma pasta, mas não no Outros.
.gif "Observação")
Observação:As técnicas aqui podem ser adaptadas para comparar seqüências de objetos de qualquer tipo.
The FileComparer classe mostrada aqui demonstra como usar uma classe de comparador personalizado juntamente com operadores de consulta padrão. A classe não se destina ao uso em cenários reais.Ele apenas utiliza o nome e tamanho em bytes de cada arquivo para determinar se o Sumário de cada pasta é idêntico ou não.Em um cenário de mundo real, você deve modificar esta comparador para executar uma verificação mais rigorosa de igualdade.
Exemplo
Module CompareDirs
Public Sub Main()
' Create two identical or different temporary folders
' on a local drive and add files to them.
' Then set these file paths accordingly.
Dim pathA As String = "C:\TestDir"
Dim pathB As String = "C:\TestDir2"
' Take a snapshot of the file system.
Dim list1 = GetFiles(pathA)
Dim list2 = GetFiles(pathB)
' Create the FileCompare object we'll use in each query
Dim myFileCompare As New FileCompare
' 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.
Dim areIdentical As Boolean = list1.SequenceEqual(list2, myFileCompare)
If areIdentical = True Then
Console.WriteLine("The two folders are the same.")
Else
Console.WriteLine("The two folders are not the same.")
End If
' Find common files in both folders. It produces a sequence and doesn't execute
' until the foreach statement.
Dim queryCommonFiles = list1.Intersect(list2, myFileCompare)
If queryCommonFiles.Count() > 0 Then
Console.WriteLine("The following files are in both folders:")
For Each fi As System.IO.FileInfo In queryCommonFiles
Console.WriteLine(fi.FullName)
Next
Else
Console.WriteLine("There are no common files in the two folders.")
End If
' Find the set difference between the two folders.
' For this example we only check one way.
Dim queryDirAOnly = list1.Except(list2, myFileCompare)
Console.WriteLine("The following files are in dirA but not dirB:")
For Each fi As System.IO.FileInfo In queryDirAOnly
Console.WriteLine(fi.FullName)
Next
' Keep the console window open in debug mode
Console.WriteLine("Press any key to exit.")
Console.ReadKey()
End Sub
' 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.
Public Class FileCompare
Implements System.Collections.Generic.IEqualityComparer(Of System.IO.FileInfo)
Public Function Equals1(ByVal x As System.IO.FileInfo, ByVal y As System.IO.FileInfo) _
As Boolean Implements System.Collections.Generic.IEqualityComparer(Of System.IO.FileInfo).Equals
If (x.Name = y.Name) And (x.Length = y.Length) Then
Return True
Else
Return False
End If
End Function
' Return a hash that reflects the comparison criteria. According to the
' rules for IEqualityComparer(Of 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 Function GetHashCode1(ByVal fi As System.IO.FileInfo) _
As Integer Implements System.Collections.Generic.IEqualityComparer(Of System.IO.FileInfo).GetHashCode
Dim s As String = fi.Name & fi.Length
Return s.GetHashCode()
End Function
End Class
' Function to retrieve a list of files. Note that this is a copy
' of the file information.
Function GetFiles(ByVal root As String) As IEnumerable(Of System.IO.FileInfo)
Return From file In My.Computer.FileSystem.GetFiles _
(root, FileIO.SearchOption.SearchAllSubDirectories, "*.*") _
Select New System.IO.FileInfo(file)
End Function
End Module
namespace QueryCompareTwoDirs
{
class CompareDirs
{
static void Main(string[] args)
{
// Create two identical or different temporary folders
// on a local drive and change these file paths.
string pathA = @"C:\TestDir";
string pathB = @"C:\TestDir2";
// Take a snapshot of the file system.
IEnumerable<System.IO.FileInfo> list1 = GetFiles(pathA);
IEnumerable<System.IO.FileInfo> list2 = GetFiles(pathB);
//A custom file comparer defined below
FileCompare myFileCompare = new FileCompare();
// 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);
if (areIdentical == true)
{
Console.WriteLine("the two folders are the same");
}
else
{
Console.WriteLine("The two folders are not the same");
}
// Find the common files. It produces a sequence and doesn't
// execute until the foreach statement.
var queryCommonFiles = list1.Intersect(list2, myFileCompare);
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.");
}
// 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);
Console.WriteLine("The following files are in list1 but not list2:");
foreach (var v in queryList1Only)
{
Console.WriteLine(v.FullName);
}
// 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;
}
}
// 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 : System.Collections.Generic.IEqualityComparer<System.IO.FileInfo>
{
public FileCompare() { }
public bool Equals(System.IO.FileInfo f1, System.IO.FileInfo f2)
{
return (f1.Name == f2.Name &&
f1.Length == f2.Length);
}
// 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(System.IO.FileInfo fi)
{
string s = String.Format("{0}{1}", fi.Name, fi.Length);
return s.GetHashCode();
}
}
}
Compilando o código
Criar um Visual Studio projeto que se destina a .NET estrutura versão 3.5. Por padrão, o projeto tem uma referência a sistema.Core.dll e um using diretiva (translation from VPE for Csharp) ou Imports demonstrativo (Visual Basic) para o namespace sistema.LINQ. Em projetos translation from VPE for Csharp, adicione um using diretiva do namespace sistema.IO.
Copie o código em seu projeto.
Pressione F5 para compilar e executar o programa.
Pressione qualquer tecla para sair da janela do console.
Programação robusta
Para operações de consulta intensivo sobre o Sumário de vários tipos de documentos e arquivos, considere usar o Windows área de trabalho Pesquisar mecanismo.