Create a new MultiDictionary. The default ordering of keys and values are used. If duplicate values are allowed, multiple copies of the same value can be associated with the same key. For example, the key "foo" could have "a", "a", and "b" associated with it. If duplicate values are not allowed, only one copies of a given value can be associated with the same key, although different keys can have the same value. For example, the key "foo" could have "a" and "b" associated with it, which key "bar" has values "b" and "c" associated with it.

Create a new MultiDictionary. If duplicate values are allowed, multiple copies of the same value can be associated with the same key. For example, the key "foo" could have "a", "a", and "b" associated with it. If duplicate values are not allowed, only one copies of a given value can be associated with the same key, although different keys can have the same value. For example, the key "foo" could have "a" and "b" associated with it, which key "bar" has values "b" and "c" associated with it.

Create a new MultiDictionary. If duplicate values are allowed, multiple copies of the same value can be associated with the same key. For example, the key "foo" could have "a", "a", and "b" associated with it. If duplicate values are not allowed, only one copies of a given value can be associated with the same key, although different keys can have the same value. For example, the key "foo" could have "a" and "b" associated with it, which key "bar" has values "b" and "c" associated with it.