Container boundary check on C#?

Hello. what is a common way to check the boundary of C# array or list<> officially?
It seems to be not supported official MS documents. Thanks.
I expected like that
int [] arr = new int[105];
bool iterate(int idx)
{
if (false == arr.RangedIn(idx))
return false;
.....
}

 

myArr.Length

will tell you the length of an array.

myList.Count

will tell you the number of elements in a list.

Code (CSharp):

1. int myIndex;
2. bool indexIsInList = myIndex > 0 && myIndex < myList.Count;
3. bool indexIsInArray = myIndex > 0 && myIndex < myArray.Length;