How to stretch in width a WPF user control to its window?

Question

I have a Window with my user control and I would like to make usercontrol width equals window width. How to do that?

The user control is a horizontal menu and contains a grid with three columns:

<ColumnDefinition Name="LeftSideMenu" Width="433"/>
<ColumnDefinition Name="Middle" Width="*"/>
<ColumnDefinition Name="RightSideMenu" Width="90"/>

That is the reason I want the window width, to stretch the user control to 100% width, with the second column relative.

EDIT:

I am using a grid, there is the code for Window:

<Window x:Class="TCI.Indexer.UI.Operacao"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:tci="clr-namespace:TCI.Indexer.UI.Controles"
    Title=" " MinHeight="550" MinWidth="675" Loaded="Load" ResizeMode="NoResize" WindowStyle="None" WindowStartupLocation="CenterScreen" WindowState="Maximized" Focusable="True"
    x:Name="windowOperacao">
    <Canvas x:Name="canv">
        <Grid>
            <tci:Status x:Name="ucStatus"/> <!-- the control which I want to stretch in width -->
        </Grid>
    </Canvas>
</Window>

Answer 1

You need to make sure your usercontrol hasn't set it's width in the usercontrol's xaml file. Just delete the Width="..." from it and you're good to go!

EDIT: This is the code I tested it with:

SOUserAnswerTest.xaml:

<UserControl x:Class="WpfApplication1.SOAnswerTest"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="300">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Name="LeftSideMenu" Width="100"/>
            <ColumnDefinition Name="Middle" Width="*"/>
            <ColumnDefinition Name="RightSideMenu" Width="90"/>
        </Grid.ColumnDefinitions>
        <TextBlock Grid.Column="0">a</TextBlock>
        <TextBlock Grid.Column="1">b</TextBlock>
        <TextBlock Grid.Column="2">c</TextBlock>
    </Grid>
</UserControl>

Window1.xaml:

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:WpfApplication1"
    Title="Window1" Height="300" Width="415">
    <Grid>

        <local:SOAnswerTest Grid.Column="0" Grid.Row="5" Grid.ColumnSpan="2"/>
    </Grid>
</Window>