概要

var dictionary1 = new Dictionary<int, string>();
var dictionary2 = new Dictionary<int, Vector3>();

Debug.Log( typeof( Dictionary<,> ).IsAssignableFrom( dictionary1.GetType().GetGenericTypeDefinition() ) );
Debug.Log( typeof( Dictionary<,> ).IsAssignableFrom( dictionary2.GetType().GetGenericTypeDefinition() ) );

参考サイト様