IList.Item Property (Int32)
.NET Framework (current version)
Gets or sets the element at the specified index.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- index
-
Type:
System.Int32
The zero-based index of the element to get or set.
| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException | index is not a valid index in the IList. |
| NotSupportedException | The property is set and the IList is read-only. |
This property provides the ability to access a specific element in the collection by using the following syntax: myCollection[index].
The C# language uses the keyword to define the indexers instead of implementing the Item property. Visual Basic implements Item as a default property, which provides the same indexing functionality.
The following example demonstrates the implementation of the IList interface to create a simple list, fixed-size list. This code is part of a larger example for the IList interface.
class SimpleList : IList { private object[] _contents = new object[8]; private int _count; public SimpleList() { _count = 0; } // IList Members public int Add(object value) { if (_count < _contents.Length) { _contents[_count] = value; _count++; return (_count - 1); } else { return -1; } } public void Clear() { _count = 0; } public bool Contains(object value) { bool inList = false; for (int i = 0; i < Count; i++) { if (_contents[i] == value) { inList = true; break; } } return inList; } public int IndexOf(object value) { int itemIndex = -1; for (int i = 0; i < Count; i++) { if (_contents[i] == value) { itemIndex = i; break; } } return itemIndex; } public void Insert(int index, object value) { if ((_count + 1 <= _contents.Length) && (index < Count) && (index >= 0)) { _count++; for (int i = Count - 1; i > index; i--) { _contents[i] = _contents[i - 1]; } _contents[index] = value; } } public bool IsFixedSize { get { return true; } } public bool IsReadOnly { get { return false; } } public void Remove(object value) { RemoveAt(IndexOf(value)); } public void RemoveAt(int index) { if ((index >= 0) && (index < Count)) { for (int i = index; i < Count - 1; i++) { _contents[i] = _contents[i + 1]; } _count--; } } public object this[int index] { get { return _contents[index]; } set { _contents[index] = value; } } // ICollection Members public void CopyTo(Array array, int index) { int j = index; for (int i = 0; i < Count; i++) { array.SetValue(_contents[i], j); j++; } } public int Count { get { return _count; } } public bool IsSynchronized { get { return false; } } // Return the current instance since the underlying store is not // publicly available. public object SyncRoot { get { return this; } } // IEnumerable Members public IEnumerator GetEnumerator() { // Refer to the IEnumerator documentation for an example of // implementing an enumerator. throw new Exception("The method or operation is not implemented."); } public void PrintContents() { Console.WriteLine("List has a capacity of {0} and currently has {1} elements.", _contents.Length, _count); Console.Write("List contents:"); for (int i = 0; i < Count; i++) { Console.Write(" {0}", _contents[i]); } Console.WriteLine(); } }
Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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