recover dropped content + edits (#3159)

* recover dropped content + edits

* Update Range.xml

Author: mairaw

xml/System/Range.xml

@@ -268,18 +268,20 @@
         <Parameter Name="length" Type="System.Int32" />
       </Parameters>
       <Docs>
-        <param name="length">The length of the collection that the range will be used with. <paramref name="length" /> has to be a positive value.</param>
+        <param name="length">A positive integer that represents the length of the collection that the range will be used with.</param>
         <summary>Calculates the start offset and length of the range object using a collection length.</summary>
-        <returns>To be added.</returns>
+        <returns>The start offset and length of the range.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
 
-For performance reasons, we don't validate the input length parameter against negative values. It is expected that `Range` will be used with collections which always have non negative length/count. We validate the range is inside the length scope though.
+For performance reasons, this method does't validate `length` to ensure that it is not negative. It does ensure that `length` is within the current `Range` instance.
 
           ]]></format>
         </remarks>
+        <exception cref="T:System.ArgumentOutOfRangeException">
+          <paramref name="length" /> is outside the bounds of the current range.</exception>
       </Docs>
     </Member>
     <Member MemberName="Start">