Dictionary<TKey, TValue>.IEnumerable.GetEnumerator Method
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Returns an enumerator that iterates through the collection.
Namespace: System.Collections.Generic
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Private Function GetEnumerator As IEnumerator
Implements IEnumerable.GetEnumerator
IEnumerator IEnumerable.GetEnumerator()
Return Value
Type: System.Collections.IEnumerator
An IEnumerator that can be used to iterate through the collection.
Implements
Remarks
For purposes of enumeration, each item is a KeyValuePair<TKey, TValue> structure representing a value and its key.
The foreach statement of the C# language (for each in C++, For Each in Visual Basic) hides the complexity of enumerators. Therefore, using foreach is recommended, instead of directly manipulating the enumerator.
Enumerators can be used to read the data in the collection, but they cannot be used to modify the underlying collection.
Initially, the enumerator is positioned before the first element in the collection. The Reset method also brings the enumerator back to this position. At this position, the Current property is undefined. Therefore, you must call the MoveNext method to advance the enumerator to the first element of the collection before reading the value of Current.
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For better performance, the enumerator returned by this property does not throw an exception if it is positioned before the first element or after the last element and the Current property is accessed; the value of the Current property is undefined. |
The Current property returns the same element until either the MoveNext or Reset method is called. MoveNext sets Current to the next element.
If MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. When the enumerator is at this position, subsequent calls to MoveNext also return false. If the last call to MoveNext returned false, Current is undefined. To set Current to the first element of the collection again, you can call Reset followed by MoveNext.
An enumerator remains valid as long as the collection remains unchanged. If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and its behavior is undefined.
The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread safe procedure. To guarantee thread safety during enumeration, you can lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.
Default implementations of collections in the System.Collections.Generic namespace are not synchronized.
This method is an O(1) operation.
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.