Format Numbers with decimal places in WPF TextBox C#

I want to format my number string entered in my textbox as (00.00) format and for that i am using following :

StringFormat={}{0:n2}

but whenever i am trying to move my cursor from left side of decimal point to right side by pressing (.) it is adding one extra point before that and my entered value is being like (10.3.00) instead of (10.30).  Please help me to handle this formatting.

Thank You