第一个构造函数
Initializes a new instance of the ArraySegment<T> structure that delimits all the elements in the specified array.
public ArraySegment(
T[] array
)
Parameters
array
Type: T[]
The array to wrap.
Remarks
This constructor creates an ArraySegment<T> that delimits all the elements of array.
That is, the Offset property of the ArraySegment<T> is 0 and its Count property is the length of array.
To create an ArraySegment<T> that delimits划界，定界限 only part of an array, use the ArraySegment<T>(T[], Int32, Int32) constructor.
The original array must be one-dimensional and must have zero-based indexing.
Multiple ArraySegment<T> instances can refer to the same original array and can overlap重叠.
第二个构造函数
Initializes a new instance of the ArraySegment<T> structure that delimits the specified range of the elements in the specified array.
初始化一个ArraySegment<T>,从array的offset下标开始，往后count个元素
public ArraySegment(
T[] array,
int offset,
int count
)
The array containing the range of elements to delimit.
The zero-based index of the first element in the range.
The number of elements in the range.
Remarks
The original array must be one-dimensional and must have zero-based indexing.
Multiple ArraySegment<T> instances can refer to the same original array and can overlap.
原文：http://www.cnblogs.com/chucklu/p/5457230.html