Add ArgumentException for Item (dotnet#5259)

Author: gewarren

xml/System.Windows.Forms/TreeNodeCollection.xml

@@ -1265,11 +1265,10 @@
         <remarks>
           <format type="text/markdown"><![CDATA[  
   
-## Remarks  
- To assign <xref:System.Windows.Forms.TreeNode> objects to a specific location, or to retrieve them from the <xref:System.Windows.Forms.TreeNodeCollection>, you can reference the collection object with a specific index value. The index value of the <xref:System.Windows.Forms.TreeNodeCollection> is a zero-based index.  
-  
-   
-  
+## Remarks
+
+To assign <xref:System.Windows.Forms.TreeNode> objects to a specific location, or to retrieve them from the <xref:System.Windows.Forms.TreeNodeCollection>, you can reference the collection object with a specific index value. The index value of the <xref:System.Windows.Forms.TreeNodeCollection> is a zero-based index.
+
 ## Examples  
  The following code example removes the first <xref:System.Windows.Forms.TreeNode> from a <xref:System.Windows.Forms.TreeView> if its <xref:System.Windows.Forms.TreeNode.Text%2A?displayProperty=nameWithType> property is set to "Node0". When a <xref:System.Windows.Forms.Button> is clicked, the first <xref:System.Windows.Forms.TreeNode> in the <xref:System.Windows.Forms.TreeView> is deleted using the <xref:System.Windows.Forms.TreeNodeCollection.RemoveAt%2A> method. This example requires that you have created a <xref:System.Windows.Forms.TreeView> and a <xref:System.Windows.Forms.Button> on a <xref:System.Windows.Forms.Form>. The first <xref:System.Windows.Forms.TreeNode> in your <xref:System.Windows.Forms.TreeView> should have a text property of "Node0."  
   
@@ -1279,7 +1278,8 @@
   
  ]]></format>
         </remarks>
-        <exception cref="T:System.ArgumentOutOfRangeException">The <paramref name="index" /> value is less than 0 or is greater than the number of tree nodes in the collection.</exception>
+        <exception cref="T:System.ArgumentOutOfRangeException">The <paramref name="index" /> value is less than 0 or is greater than the last index in the collection.</exception>
+        <exception cref="T:System.ArgumentException">The <see cref="T:System.Windows.Forms.TreeNode" /> that's being assigned to this index is already assigned to a different index or to a different <see cref="T:System.Windows.Forms.TreeView" /> control.</exception>
         <altmember cref="P:System.Windows.Forms.TreeNodeCollection.Count" />
       </Docs>
     </Member>