Need to disable window size changes in xaml file with only user control in it.

Hi 
we want to restrict the window size of user control.
In our application we are using a user control  as below. we are not able to disable size changes  of window.
We cann't use window tag in this page. Though we are setting height and width for user control does are not working.
Is there any alternative.
<UserControlx:Class="WpfApplication18.UserControl1"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"mc:Ignorable="d"d:DesignHeight="300"d:DesignWidth="300"Width="100"Height="100">