Array.FindIndex has incorrect ArgumentOutOfRangeException description for 'startIndex' parameter.

[Fast-Nick]

Example of what it looks like today (see bottom line of documentation):

        //     .........
        // Exceptions:
        //   T:System.ArgumentNullException:
        //     array is null. -or- match is null.
        //
        //   T:System.ArgumentOutOfRangeException:
        //     startIndex is outside the range of valid indexes for array.
        public static int FindIndex<T>(T[] array, int startIndex, Predicate<T> match);

It effectively says that the method accepts [0 <= startIndex < Length] with Length exclusive.
But what the method actually accepts is [0 <= startIndex <= Length] with Length inclusive.

The real behavior of the startIndex is identical to String.Substring, which has the following description instead:

        //   T:System.ArgumentOutOfRangeException:
        //     startIndex is less than zero or greater than the length of this instance.

To be correct and easy to understand the FindIndex documentation should thus say:

        //     startIndex is less than zero or greater than the length of the array.

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[Fast-Nick]

Adding a draft for now - it does fix the exact issue described, but the phrase "... is outside the range of valid indexes for ..." exists on a lot of other Array methods too, so it's probably ideal to go through all of them and make sure the phrasing is consistent for all methods which have this bound-check behavior.

...but I don't have time to do that today so will look at it / go through all methods later.