IReadOnlyDictionary(TKey, TValue).Item Property
Gets the element that has the specified key in the read-only dictionary.
Assembly: mscorlib (in mscorlib.dll)
This property lets you access a specific element in the collection by using the following syntax: myCollection[key] (myCollection(key) in Visual Basic).
Implementations can vary in how they determine the equality of objects: for example, the class that implements IReadOnlyDictionary(TKey, TValue) might use the Comparer(T).Default property, or it might implement the IComparer(T) method.
Implementations can vary in whether they allow key to be a null reference (Nothing in Visual Basic).