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Como: comparar o conteúdo das duas pastas (LINQ)

Este exemplo demonstra três maneiras para comparar duas listagens de arquivos:

  • Consultando um valor booleano que especifica se as duas listas de arquivos 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 outro.

    ObservaçãoObservação

    As técnicas mostradas aqui podem ser adaptadas para comparar seqüências de objetos de qualquer tipo.

O FileComparer classe mostrada aqui demonstra como usar uma classe de comparador personalizado juntamente com os operadores de consulta padrão.A classe não se destina ao uso em cenários do mundo real.Ela simplesmente usa o nome e o comprimento em bytes de cada arquivo para determinar se o conteúdo de cada pasta é idêntico ou não.Em um cenário do 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 dir1 As New System.IO.DirectoryInfo(pathA)
        Dim dir2 As New System.IO.DirectoryInfo(pathB)

        Dim list1 = dir1.GetFiles("*.*", System.IO.SearchOption.AllDirectories)
        Dim list2 = dir2.GetFiles("*.*", System.IO.SearchOption.AllDirectories)

        ' 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
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";

            System.IO.DirectoryInfo dir1 = new System.IO.DirectoryInfo(pathA);
            System.IO.DirectoryInfo dir2 = new System.IO.DirectoryInfo(pathB);

            // Take a snapshot of the file system.
            IEnumerable<System.IO.FileInfo> list1 = dir1.GetFiles("*.*", System.IO.SearchOption.AllDirectories);
            IEnumerable<System.IO.FileInfo> list2 = dir2.GetFiles("*.*", System.IO.SearchOption.AllDirectories);

            //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 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 o projeto que se destina a.NET Framework versão 3.5.Por padrão, o projeto tem uma referência a System.Core.dll e um using diretiva (C#) ou Imports (Visual Basic) da declaração do namespace System. LINQ.No C# projetos, adicione um using diretriz para o namespace System. 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 conteúdo de vários tipos de documentos e arquivos, considere o uso de O Windows Desktop Search engine.

Consulte também

Conceitos

LINQ to Objects

LINQ e diretórios de arquivos