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//---------------------------------------------------------------------------
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
//
// Description: PartialList is used when the developer needs to pass an IList range to
// a function that takes generic IList interface.
//
//
// History:
// 06/25/2004 : mleonov - Created
//
//---------------------------------------------------------------------------
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
namespace MS.Internal
{
/// <summary>
/// PartialList is used when someone needs to pass an IList range to
/// a function that takes generic IList interface. It implemented a read-only subset of IList.
/// </summary>
internal class PartialList<T> : IList<T>
{
private IList<T> _list;
private int _initialIndex;
private int _count;
/// <summary>
/// Convenience constructor for taking in an entire list. Useful for creating a read-only
/// version of the list.
/// </summary>
public PartialList(IList<T> list)
{
_list = list;
_initialIndex = 0;
_count = list.Count;
}
public PartialList(IList<T> list, int initialIndex, int count)
{
// make sure early that the caller didn't miscalculate index and count
Debug.Assert(initialIndex >= 0 && initialIndex + count <= list.Count);
_list = list;
_initialIndex = initialIndex;
_count = count;
}
#if !PRESENTATION_CORE
/// <summary>
/// Creates new PartialList object only for true partial ranges.
/// Otherwise, returns the original list.
/// </summary>
public static IList<T> Create(IList<T> list, int initialIndex, int count)
{
if (list == null)
return null;
if (initialIndex == 0 && count == list.Count)
return list;
return new PartialList<T>(list, initialIndex, count);
}
#endif
#region IList<T> Members
public void RemoveAt(int index)
{
// PartialList is read only.
throw new NotSupportedException();
}
public void Insert(int index, T item)
{
// PartialList is read only.
throw new NotSupportedException();
}
public T this[int index]
{
get
{
return _list[index + _initialIndex];
}
set
{
// PartialList is read only.
throw new NotSupportedException();
}
}
public int IndexOf(T item)
{
int index = _list.IndexOf(item);
if (index == -1 || index < _initialIndex || index - _initialIndex >= _count)
return -1;
return index - _initialIndex;
}
#endregion
#region ICollection<T> Members
public bool IsReadOnly
{
get
{
return true;
}
}
public void Clear()
{
// PartialList is read only.
throw new NotSupportedException();
}
public void Add(T item)
{
// PartialList is read only.
throw new NotSupportedException();
}
public bool Contains(T item)
{
return IndexOf(item) != -1;
}
public bool Remove(T item)
{
// PartialList is read only.
throw new NotSupportedException();
}
public int Count
{
get
{
return _count;
}
}
public void CopyTo(T[] array, int arrayIndex)
{
if (arrayIndex < 0)
throw new ArgumentOutOfRangeException("arrayIndex");
for (int i = 0; i < _count; ++i)
array[arrayIndex + i] = this[i];
}
#endregion
#region IEnumerable<T> Members
IEnumerator<T> IEnumerable<T>.GetEnumerator()
{
for (int i = _initialIndex; i < _initialIndex + _count; ++i)
yield return _list[i];
}
#endregion
#region IEnumerable Members
IEnumerator IEnumerable.GetEnumerator()
{
return ((IEnumerable<T>)this).GetEnumerator();
}
#endregion
}
}
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