IOrderedDictionary.GetEnumerator メソッド

定義

名前空間:

System.Collections.Specialized

アセンブリ:

System.Collections.Specialized.dll

IOrderedDictionary コレクションを反復処理する列挙子を返します。

public:
 System::Collections::IDictionaryEnumerator ^ GetEnumerator();

public System.Collections.IDictionaryEnumerator GetEnumerator ();

abstract member GetEnumerator : unit -> System.Collections.IDictionaryEnumerator

Public Function GetEnumerator () As IDictionaryEnumerator

戻り値

IDictionaryEnumerator

IDictionaryEnumerator コレクション全体の IOrderedDictionary。

実装

GetEnumerator()

例

次のコード例は、 クラスに基づく単純 IOrderedDictionary な の実装を ArrayList 示しています。 実装された IOrderedDictionary には、キーとして名、値として姓が格納され、各名が一意であるという要件が追加されます。 このコードは、 クラスに対して提供されるより大きなコード例の IOrderedDictionary 一部です。

public ref class PeopleEnum : IDictionaryEnumerator
{
private:
    // Enumerators are positioned before the first element
    // until the first MoveNext() call.
    int position;
    ArrayList^ _people;

public:
    PeopleEnum(ArrayList^ list)
    {
        this->Reset();
        _people = list;
    }

    virtual bool MoveNext()
    {
        position++;
        return (position < _people->Count);
    }

    virtual void Reset()
    {
        position = -1;
    }

    virtual property Object^ Current
    {
        Object^ get()
        {
            try
            {
                return _people[position];
            }
            catch (IndexOutOfRangeException^)
            {
                throw gcnew InvalidOperationException();
            }
        }
    }

    virtual property DictionaryEntry Entry
    {
        DictionaryEntry get()
        {
            return (DictionaryEntry)(Current);
        }
    }

    virtual property Object^ Key
    {
        Object^ get()
        {
            try
            {
                return ((DictionaryEntry^)_people[position])->Key;
            }
            catch (IndexOutOfRangeException^)
            {
                throw gcnew InvalidOperationException();
            }
        }
    }

    virtual property Object^ Value
    {
        Object^ get()
        {
            try
            {
                return ((DictionaryEntry^)_people[position])->Value;
            }
            catch (IndexOutOfRangeException^)
            {
                throw gcnew InvalidOperationException();
            }
        }
    }
};

public ref class People : IOrderedDictionary
{
private:
    ArrayList^ _people;

public:
    People(int numItems)
    {
        _people = gcnew ArrayList(numItems);
    }

    int IndexOfKey(Object^ key)
    {
        for (int i = 0; i < _people->Count; i++)
        {
            if (((DictionaryEntry^)_people[i])->Key == key)
                return i;
        }

        // key not found, return -1.
        return -1;
    }

    virtual property Object^ default[Object^]
    {
        Object^ get(Object^ key)
        {
            return ((DictionaryEntry^)_people[IndexOfKey(key)])->Value;
        }
        void set(Object^ key, Object^ value)
        {
            _people[IndexOfKey(key)] = gcnew DictionaryEntry(key, value);
        }
    }

    // IOrderedDictionary Members
    virtual IDictionaryEnumerator^ GetEnumerator()
    {
        return gcnew PeopleEnum(_people);
    }

    virtual void Insert(int index, Object^ key, Object^ value)
    {
        if (IndexOfKey(key) != -1)
        {
            throw gcnew ArgumentException("An element with the same key already exists in the collection.");
        }
        _people->Insert(index, gcnew DictionaryEntry(key, value));
    }

    virtual void RemoveAt(int index)
    {
        _people->RemoveAt(index);
    }

    virtual property Object^ default[int]
    {
        Object^ get(int index)
        {
            return ((DictionaryEntry^)_people[index])->Value;
        }
        void set(int index, Object^ value)
        {
            Object^ key = ((DictionaryEntry^)_people[index])->Key;
            _people[index] = gcnew DictionaryEntry(key, value);
        }
    }

    // IDictionary Members

    virtual void Add(Object^ key, Object^ value)
    {
        if (IndexOfKey(key) != -1)
        {
            throw gcnew ArgumentException("An element with the same key already exists in the collection.");
        }
        _people->Add(gcnew DictionaryEntry(key, value));
    }

    virtual void Clear()
    {
        _people->Clear();
    }

    virtual bool Contains(Object^ key)
    {
        if (IndexOfKey(key) == -1)
        {
            return false;
        }
        else
        {
            return true;
        }
    }

    virtual property bool IsFixedSize
    {
        bool get()
        {
            return false;
        }
    }

    virtual property bool IsReadOnly
    {
        bool get()
        {
            return false;
        }
    }

    virtual property ICollection^ Keys
    {
        ICollection^ get()
        {
            ArrayList^ KeyCollection = gcnew ArrayList(_people->Count);
            for (int i = 0; i < _people->Count; i++)
            {
                KeyCollection->Add( ((DictionaryEntry^)_people[i])->Key );
            }
            return KeyCollection;
        }
    }

    virtual void Remove(Object^ key)
    {
        _people->RemoveAt(IndexOfKey(key));
    }

    virtual property ICollection^ Values
    {
        ICollection ^get()
        {
            ArrayList^ ValueCollection = gcnew ArrayList(_people->Count);
            for (int i = 0; i < _people->Count; i++)
            {
                ValueCollection->Add( ((DictionaryEntry^)_people[i])->Value );
            }
            return ValueCollection;
        }
    }

    // ICollection Members

    virtual void CopyTo(Array^ array, int index)
    {
        _people->CopyTo(array, index);
    }

    virtual property int Count
    {
        int get()
        {
            return _people->Count;
        }
    }

    virtual property bool IsSynchronized
    {
        bool get()
        {
            return _people->IsSynchronized;
        }
    }

    virtual property Object^ SyncRoot
    {
        Object^ get()
        {
            return _people->SyncRoot;
        }
    }

    // IEnumerable Members

    virtual IEnumerator^ IfcGetEnumerator() = IEnumerable::GetEnumerator
    {
        return (IEnumerator^) gcnew PeopleEnum(_people);
    }
};

public class People : IOrderedDictionary
{
    private ArrayList _people;

    public People(int numItems)
    {
        _people = new ArrayList(numItems);
    }

    public int IndexOfKey(object key)
    {
        for (int i = 0; i < _people.Count; i++)
        {
            if (((DictionaryEntry)_people[i]).Key == key)
                return i;
        }

        // key not found, return -1.
        return -1;
    }

    public object this[object key]
    {
        get
        {
            return ((DictionaryEntry)_people[IndexOfKey(key)]).Value;
        }
        set
        {
            _people[IndexOfKey(key)] = new DictionaryEntry(key, value);
        }
    }

    // IOrderedDictionary Members
    public IDictionaryEnumerator GetEnumerator()
    {
        return new PeopleEnum(_people);
    }

    public void Insert(int index, object key, object value)
    {
        if (IndexOfKey(key) != -1)
        {
            throw new ArgumentException("An element with the same key already exists in the collection.");
        }
        _people.Insert(index, new DictionaryEntry(key, value));
    }

    public void RemoveAt(int index)
    {
        _people.RemoveAt(index);
    }

    public object this[int index]
    {
        get
        {
            return ((DictionaryEntry)_people[index]).Value;
        }
        set
        {
            object key = ((DictionaryEntry)_people[index]).Key;
            _people[index] = new DictionaryEntry(key, value);
        }
    }
    // IDictionary Members

    public void Add(object key, object value)
    {
        if (IndexOfKey(key) != -1)
        {
            throw new ArgumentException("An element with the same key already exists in the collection.");
        }
        _people.Add(new DictionaryEntry(key, value));
    }

    public void Clear()
    {
        _people.Clear();
    }

    public bool Contains(object key)
    {
        if (IndexOfKey(key) == -1)
        {
            return false;
        }
        else
        {
            return true;
        }
    }

    public bool IsFixedSize
    {
        get
        {
            return false;
        }
    }

    public bool IsReadOnly
    {
        get
        {
            return false;
        }
    }

    public ICollection Keys
    {
        get
        {
            ArrayList KeyCollection = new ArrayList(_people.Count);
            for (int i = 0; i < _people.Count; i++)
            {
                KeyCollection.Add( ((DictionaryEntry)_people[i]).Key );
            }
            return KeyCollection;
        }
    }

    public void Remove(object key)
    {
        _people.RemoveAt(IndexOfKey(key));
    }

    public ICollection Values
    {
        get
        {
            ArrayList ValueCollection = new ArrayList(_people.Count);
            for (int i = 0; i < _people.Count; i++)
            {
                ValueCollection.Add( ((DictionaryEntry)_people[i]).Value );
            }
            return ValueCollection;
        }
    }

    // ICollection Members

    public void CopyTo(Array array, int index)
    {
        _people.CopyTo(array, index);
    }

    public int Count
    {
        get
        {
            return _people.Count;
        }
    }

    public bool IsSynchronized
    {
        get
        {
            return _people.IsSynchronized;
        }
    }

    public object SyncRoot
    {
        get
        {
            return _people.SyncRoot;
        }
    }

    // IEnumerable Members

    IEnumerator IEnumerable.GetEnumerator()
    {
        return new PeopleEnum(_people);
    }
}

public class PeopleEnum : IDictionaryEnumerator
{
    public ArrayList _people;

    // Enumerators are positioned before the first element
    // until the first MoveNext() call.
    int position = -1;

    public PeopleEnum(ArrayList list)
    {
        _people = list;
    }

    public bool MoveNext()
    {
        position++;
        return (position < _people.Count);
    }

    public void Reset()
    {
        position = -1;
    }

    public object Current
    {
        get
        {
            try
            {
                return _people[position];
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException();
            }
        }
    }

    public DictionaryEntry Entry
    {
        get
        {
            return (DictionaryEntry)Current;
        }
    }

    public object Key
    {
        get
        {
            try
            {
                return ((DictionaryEntry)_people[position]).Key;
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException();
            }
        }
    }

    public object Value
    {
        get
        {
            try
            {
                return ((DictionaryEntry)_people[position]).Value;
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException();
            }
        }
    }
}

Public Class People
    Implements IOrderedDictionary
    Private _people As ArrayList

    Public Sub New(ByVal numItems As Integer)
        _people = New ArrayList(numItems)
    End Sub

    Public Function IndexOfKey(ByVal key As Object) As Integer
        Dim i As Integer
        For i = 0 To _people.Count - 1
            If CType(_people(i), DictionaryEntry).Key = key Then
                Return i
            End If
        Next i

        ' key not found, return -1.
        Return -1
    End Function

    ' IOrderedDictionary Members
    Public Function GetEnumerator() As IDictionaryEnumerator _
        Implements IOrderedDictionary.GetEnumerator

        Return New PeopleEnum(_people)
    End Function

    Public Sub Insert(ByVal index As Integer, ByVal key As Object, _
        ByVal value As Object) Implements IOrderedDictionary.Insert

        If Not IndexOfKey(key) = -1 Then
            Throw New ArgumentException("An element with the same key already exists in the collection.")
        End If
        _people.Insert(index, New DictionaryEntry(key, value))
    End Sub

    Public Sub RemoveAt(ByVal index As Integer) _
        Implements IOrderedDictionary.RemoveAt

        _people.RemoveAt(index)
    End Sub

    Public Property Item(ByVal index As Integer) As Object _
        Implements IOrderedDictionary.Item

        Get
            Return CType(_people(index), DictionaryEntry).Value
        End Get
        Set(ByVal value As Object)
            Dim key As Object = CType(_people(index), DictionaryEntry).Key
            _people(index) = New DictionaryEntry(key, value)
        End Set
    End Property

    ' IDictionary Members
    Public Function IDictionaryGetEnumerator() As IDictionaryEnumerator _
    Implements IDictionary.GetEnumerator

        Return New PeopleEnum(_people)
    End Function

    Public Property Item(ByVal key As Object) As Object _
        Implements IDictionary.Item

        Get
            Return CType(_people(IndexOfKey(key)), DictionaryEntry).Value
        End Get
        Set(ByVal value)
            _people(IndexOfKey(key)) = New DictionaryEntry(key, value)
        End Set
    End Property


    Public Sub Add(ByVal key As Object, ByVal value As Object) _
        Implements IDictionary.Add

        If Not IndexOfKey(key) = -1 Then
            Throw New ArgumentException("An element with the same key already exists in the collection.")
        End If

        _people.Add(New DictionaryEntry(key, value))
    End Sub

    Public Sub Clear() Implements IDictionary.Clear
        _people.Clear()
    End Sub

    Public Function Contains(ByVal key As Object) As Boolean _
        Implements IDictionary.Contains

        If IndexOfKey(key) = -1 Then
            Return False
        Else
            Return True
        End If
    End Function

    Public ReadOnly Property IsFixedSize() As Boolean _
        Implements IDictionary.IsFixedSize

        Get
            Return False
        End Get
    End Property

    Public ReadOnly Property IsReadOnly() As Boolean _
        Implements IDictionary.IsReadOnly
        Get
            Return False
        End Get
    End Property

    Public ReadOnly Property Keys() As ICollection _
        Implements IDictionary.Keys
        Get
            Dim KeyCollection As ArrayList = New ArrayList(_people.Count)
            Dim i As Integer
            For i = 0 To _people.Count - 1
                KeyCollection.Add( CType(_people(i), DictionaryEntry).Key )
            Next i
            Return KeyCollection
        End Get
    End Property

    Public Sub Remove(ByVal key As Object) _
        Implements IDictionary.Remove

        _people.RemoveAt(IndexOfKey(key))
    End Sub

    Public ReadOnly Property Values() As ICollection _
        Implements IDictionary.Values
        Get
            Dim ValueCollection As ArrayList = New ArrayList(_people.Count)
            Dim i As Integer
            For i = 0 To _people.Count - 1
                ValueCollection.Add( CType(_people(i), DictionaryEntry).Value )
            Next i
            Return ValueCollection
        End Get
    End Property

    ' ICollection Members
    Public Sub CopyTo(ByVal array As Array, ByVal index As Integer) _
    Implements ICollection.CopyTo

        _people.CopyTo(Array, index)
    End Sub

    Public ReadOnly Property Count() As Integer _
        Implements ICollection.Count

        Get
            Return _people.Count
        End Get
    End Property

    Public ReadOnly Property IsSynchronized() As Boolean _
        Implements ICollection.IsSynchronized

        Get
            Return _people.IsSynchronized
        End Get
    End Property

    Public ReadOnly Property SyncRoot() As Object _
        Implements ICollection.SyncRoot

        Get
            Return _people.SyncRoot
        End Get
    End Property

    ' IEnumerable Members
    Public Function IEnumerableGetEnumerator() As IEnumerator _
        Implements IEnumerable.GetEnumerator

        Return New PeopleEnum(_people)
    End Function
End Class

Public Class PeopleEnum
    Implements IDictionaryEnumerator

    Public _people As ArrayList

    ' Enumerators are positioned before the first element
    ' until the first MoveNext() call.
    Dim position As Integer = -1

    Public Sub New(ByVal list As ArrayList)
        _people = list
    End Sub

    Public Function MoveNext() As Boolean _
        Implements IEnumerator.MoveNext

        position = position + 1
        Return (position < _people.Count)
    End Function

    Public Sub Reset() _
        Implements IEnumerator.Reset

        position = -1
    End Sub

    Public ReadOnly Property Current() As Object _
        Implements IEnumerator.Current

        Get
            Try
                Return _people(position)
            Catch e As IndexOutOfRangeException
                Throw New InvalidOperationException()
            End Try
        End Get
    End Property

    Public ReadOnly Property Entry() As DictionaryEntry _
        Implements IDictionaryEnumerator.Entry
        Get
            Return CType(Current, DictionaryEntry)
        End Get
    End Property

    Public ReadOnly Property Key() As Object _
        Implements IDictionaryEnumerator.Key

        Get
            Try
                Return CType(_people(position), DictionaryEntry).Key
            Catch e As IndexOutOfRangeException
                Throw New InvalidOperationException()
            End Try
        End Get
    End Property

    Public ReadOnly Property Value() As Object _
        Implements IDictionaryEnumerator.Value

        Get
            Try
                Return CType(_people(position), DictionaryEntry).Value
            Catch e As IndexOutOfRangeException
                Throw New InvalidOperationException()
            End Try
        End Get
    End Property
End Class

注釈

C# 言語の foreach ステートメント (Visual Basic の場合は for each) を使用することで列挙子の複雑さを回避できます。 したがって、列挙子を直接操作するのではなく、 を使用 foreach することをお勧めします。

列挙子を使用すると、コレクション内のデータを読み取ることができますが、基になるコレクションを変更することはできません。

最初、列挙子はコレクションの先頭の要素の前に位置付けられます。 また、Reset メソッドは、列挙子を最初の位置に戻します。 この位置では、Current プロパティは定義されていません。 そのため、MoveNext の値を読み取る前に、Current を呼び出して列挙子をコレクションの最初の要素に進める必要があります。

Current は、MoveNext または Reset が呼び出されるまでは同じオブジェクトを返します。 MoveNext は、Current を次の要素に進めます。

MoveNext がコレクションの末尾を通過した場合、列挙子がコレクション内の最後の要素の後に配置され、MoveNext は false を返します。 列挙子がこの位置にある場合、後続の MoveNext 呼び出しも false を返します。 が返された falseCurrent の最後のMoveNext呼び出しが未定義の場合。 コレクションの先頭の要素に再び Current を設定するには、先に Reset を呼び出してから MoveNext を呼び出します。

列挙子は、コレクションが変更されない限り有効です。 コレクションに対して変更 (要素の追加、変更、削除など) が行われると、列挙子は回復不可能な無効状態になり、その動作は未定義になります。

列挙子はコレクションに排他アクセスできないため、コレクションの列挙処理は本質的にスレッド セーフな処理ではありません。 列挙処理でスレッド セーフを確保するには、列挙処理が終わるまでコレクションをロックできます。 コレクションに対し複数のスレッドがアクセスして読み取りや書き込みを行うことができるようにするには、独自に同期化を実装する必要があります。