Closing Active MDI child

[Sumit]

Hi all,

I have an MDI form in which i open an MDI child.

I am providing a Log Off functionality in my Menu that i have on the
MDI form. On Click event of "Log Off" i am writing the following code:

Form[] childFormArray= this.MdiChildren;
if (childFormArray.Length > 0)
foreach (Form childForm in childFormArray)
childForm.Close();

Now I have just one active child so "childFormArray.Length" = 1

When the control goes to line childForm.Close(), it goes to the Dispose
method of the child form but when it executes the line
"base.Dispose( disposing );" it is throwing an exception that
"Object reference not set to an instance of an object".

Can anyone tell me why it is displaying me such an error.
Kindly Help !!

Sumit