PropertyCollection.IDictionary.Item[Object] Property
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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.Item
- key
- Object
The key of the element to get or set.
The element with the specified key.
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.
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
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.
Продукт | Версії |
---|---|
.NET | 8 (package-provided), 9 (package-provided) |
.NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7 (package-provided), 4.7, 4.7.1 (package-provided), 4.7.1, 4.7.2 (package-provided), 4.7.2, 4.8 (package-provided), 4.8, 4.8.1 |
.NET Standard | 2.0 (package-provided) |
Windows Desktop | 3.0, 3.1, 5, 6, 7, 8, 9 |
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