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Comment : comparer le contenu de deux dossiers (LINQ)

Cet exemple présente trois façons de comparer deux listes de fichiers :

  • En recherchant une valeur booléenne qui spécifie si les deux listes de fichiers sont identiques.

  • En recherchant l'intersection pour récupérer les fichiers qui se trouvent dans les deux dossiers.

  • En recherchant les différences pour récupérer les fichiers qui sont dans un dossier mais pas l'autre.

    Notes

    Les techniques présentées ici peuvent être adaptées pour comparer des séquences d'objets de tout type.

La classe FileComparer présentée ici montre comment utiliser une classe de comparateur personnalisée avec les opérateurs de requête standard. La classe n'est pas destinée à être utilisée dans des scénarios réels. Elle utilise simplement le nom et la longueur en octets de chaque fichier pour déterminer si le contenu de chaque dossier est identique ou non. Dans un scénario réel, vous devez modifier ce comparateur pour effectuer un contrôle d'égalité plus rigoureux.

Exemple

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();
        }
    }
}

Compilation du code

  • Créez un projet Visual Studio qui cible la version 3.5 du .NET Framework. Par défaut, le projet possède une référence à System.Core.dll et une directive using (C#) ou une instruction Imports (Visual Basic) pour l'espace de noms System.Linq. Dans les projets C#, ajoutez une directive using pour l'espace de noms System.IO.

  • Copiez le code dans votre projet.

  • Appuyez sur F5 pour compiler et exécuter le programme.

  • Appuyez sur une touche pour quitter la fenêtre de console.

Programmation fiable

Pour les opérations de requête intensives sur le contenu de plusieurs types de documents et de fichiers, envisagez d'utiliser le moteur de recherche Windows Desktop Search (en anglais).

Voir aussi

Concepts

LINQ to Objects

LINQ et répertoires de fichiers