PropertyCollection.IDictionary.Item[Object] Property
Definition
Important
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Gets or sets the element with the specified key.
property System::Object ^ System::Collections::IDictionary::Item[System::Object ^] { System::Object ^ get(System::Object ^ key); void set(System::Object ^ key, System::Object ^ value); };object? System.Collections.IDictionary.Item[object key] { get; set; }object System.Collections.IDictionary.Item[object key] { get; set; }member this.System.Collections.IDictionary.Item(obj) : obj with get, set Property Item(key As Object) As Object Implements IDictionary.ItemParameters
- key
- Object
The key of the element to get or set.
Property Value
The element with the specified key.
Implements
Exceptions
key is null.
The property is set and the IDictionary object is read-only.
-or-
The property is set, key does not exist in the collection, and the IDictionary has a fixed size.
Examples
The following example shows how to implement the Item[] property. This code example is part of a larger example provided for the IDictionary class.
public:
virtual property Object^ default[Object^]
{
Object^ get(Object^ key)
{
// If this key is in the dictionary, return its value.
int index;
if (TryGetIndexOfKey(key, &index))
{
// The key was found; return its value.
return items[index]->Value;
}
else
{
// The key was not found; return null.
return nullptr;
}
}
void set(Object^ key, Object^ value)
{
// If this key is in the dictionary, change its value.
int index;
if (TryGetIndexOfKey(key, &index))
{
// The key was found; change its value.
items[index]->Value = value;
}
else
{
// This key is not in the dictionary; add this
// key/value pair.
Add(key, value);
}
}
}
public object this[object key]
{
get
{
// If this key is in the dictionary, return its value.
Int32 index;
if (TryGetIndexOfKey(key, out index))
{
// The key was found; return its value.
return items[index].Value;
}
else
{
// The key was not found; return null.
return null;
}
}
set
{
// If this key is in the dictionary, change its value.
Int32 index;
if (TryGetIndexOfKey(key, out index))
{
// The key was found; change its value.
items[index].Value = value;
}
else
{
// This key is not in the dictionary; add this key/value pair.
Add(key, value);
}
}
}
Public Property Item(ByVal key As Object) As Object Implements IDictionary.Item
Get
' If this key is in the dictionary, return its value.
Dim index As Integer
If TryGetIndexOfKey(key, index) Then
' The key was found return its value.
Return items(index).Value
Else
' The key was not found return null.
Return Nothing
End If
End Get
Set(ByVal value As Object)
' If this key is in the dictionary, change its value.
Dim index As Integer
If TryGetIndexOfKey(key, index) Then
' The key was found change its value.
items(index).Value = value
Else
' This key is not in the dictionary add this key/value pair.
Add(key, value)
End If
End Set
End Property
Remarks
This property provides the ability to access a specific element in the collection by using the following syntax: myCollection[key].
You can also use the Item[] property to add new elements by setting the value of a key that does not exist in the dictionary (for example, myCollection["myNonexistentKey"] = myValue). However, if the specified key already exists in the dictionary, setting the Item[] property overwrites the old value. In contrast, the Add method does not modify existing elements.
