Gets the number of elements contained in the ICollection.(Inherited from ICollection) The implementing class must have a means to compare keys. The foreach statement is a wrapper around the enumerator, which only allows reading from, not writing to, the collection.īecause keys can be inherited and their behavior changed, their absolute uniqueness cannot be guaranteed by comparisons using the Equals method.

Instead, the element type is KeyValuePair. Since each element of the IDictionary is a key/value pair, the element type is not the type of the key or the type of the value. The foreach statement of the C# language ( For Each in Visual Basic, for each in C++) returns an object of the type of the elements in the collection. The IDictionary interface allows the contained keys and values to be enumerated, but it does not imply any particular sort order. The value can be null and does not have to be unique. Implementations can vary in whether they allow key to be null. The IDictionary interface is the base interface for generic collections of key/value pairs.Įach element is a key/value pair stored in a KeyValuePair object.Įach pair must have a unique key. The example shows how to use the TryGetValue method as a more efficient way to retrieve values if a program often must try key values that are not in the dictionary, and how to use the ContainsKey method to test whether a key exists prior to calling the Add method.įinally, the example shows how to enumerate the keys and values in the dictionary, and how to enumerate the values alone using the Values property. The example uses the Item property (the indexer in C#) to retrieve values, demonstrating that a KeyNotFoundException is thrown when a requested key is not present, and showing that the value associated with a key can be replaced. The example demonstrates that the Add method throws ArgumentException when attempting to add a duplicate key. The code example uses the Add method to add some elements. The following code example creates an empty Dictionary of strings, with string keys, and accesses it through the IDictionary interface.

ICollection> IEnumerable> IEnumerable IEnumerable IEnumerable IEnumerable IEnumerable IEnumerable IEnumerable IEnumerable Examples

Expected a dict object