The value parameter is assumed to point to an array representing a string encoded in ASCII; that is, the string is encoded using the ANSI code page.
If length is zero, the new instance is initialized to the empty string ("").
This constructor processes characters from value starting at startIndex and ending at (startIndex + length - 1).
If the specified range is outside of the memory allocated for the sequence of characters, the behavior of this constructor is system dependent. For example, such a situation might cause an access violation.
In C#, this constructor is defined only in the context of unsafe code.