Support types that present contiguous region of memory

While working with large amount of text data such as logs, I have to use tasks of string frequently. Moreover, these tasks takes substring of large string as parameter. So, I have to create new instance of string on each invokation just for passing to the model. Would be better to use such clases as CharSequence in Kotiln and Memory in C# in terms of perfomance? Anyway, framework doesn't support that types at the moment