Silverlight 4 how to detect the screen size and bind to a grid

I can't get my application to resize the screen correctly. here is my xaml

<Grid x:Name="LayoutRoot"
      Background="White"
      DataContext="{Binding Source={StaticResource ViewModel}}"
      MinHeight="473"
      MinWidth="1200"
      MaxHeight="600"
      MaxWidth="1366">
<i:Interaction.Triggers>
    <i:EventTrigger EventName="SizeChanged">
        <ei:CallMethodAction MethodName="WndSizeChanged"
                             TargetObject="{Binding}" />
    </i:EventTrigger>
</i:Interaction.Triggers>

    <Grid.ColumnDefinitions>
        <ColumnDefinition  Width="300*" />
        <ColumnDefinition  Width="189*" />
        <ColumnDefinition  Width="720*" />
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition  Height="101*" />
        <RowDefinition  Height="372*" />
    </Grid.RowDefinitions>

 <sdk:DataGrid Grid.Row="1"
                  Grid.Column="0"
                  Grid.ColumnSpan="3"
                  AutoGenerateColumns="False"
                  HorizontalAlignment="Left"
                  Height="Auto"
                  Width="Auto"
                  Name="dataGrid_Columns"
                  VerticalAlignment="Top"
                  ItemsSource="{Binding Path=LstDetails}"
                  RowDetailsVisibilityMode="VisibleWhenSelected"
                  IsReadOnly="True"
                  HeadersVisibility="All"
                  HorizontalScrollBarVisibility="Visible"
                  VerticalScrollBarVisibility="Visible"
                  CanUserReorderColumns="True"
                  CanUserResizeColumns="True"
                  CanUserSortColumns="True">

       .....more code nested in here.......
   </sdk:DataGrid>

I have tried putting auto on the user control, and also in the grid, nothi开发者_如何学Gong is working. If I take out thet min and max, then it goes off the page. That event I put on there, only fires after you resize it. I would assume because this is a user control inside a shell. I am using prism. I found an example to detect the height and width, but it doesn't work initially. When I bind the height and width to double properties, then the event never fires at all. I am running out of ideas. I have found ways to put in code behind the actual width and height. I really want to avoid code behind, but even that did not work. I know the problem has to do with the datagrid, because this is dynamic and will grow or shrink based on filters. Any help is greatly appreciated. Thanks.

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This is the best solution I can come up with. It works, but probably not nice since the VM now knows something about the View (correct me if I am wrong). so here is my VM:

    public void WndSizeChanged(object sender, EventArgs e)
    {
        this.setHeightWidth();
    }
    private void setHeightWidth()
    {
        this.WindowHeight = (Application.Current.RootVisual as FrameworkElement).ActualHeight - 125;
        this.WindowWidth = (Application.Current.RootVisual as FrameworkElement).ActualWidth - 108;
    }

    public double WindowHeight{get;set;}

    public double WindowWidth{get;set;}

and in my view:

<Grid x:Name="LayoutRoot"
      Background="White"
      DataContext="{Binding Source={StaticResource ViewModel}}"
      Height="{Binding Path=WindowHeight, Mode=TwoWay}"
      Width="{Binding Path=WindowWidth, Mode=TwoWay}">

        <i:Interaction.Triggers>
        <i:EventTrigger EventName="LayoutUpdated">
                <ei:CallMethodAction MethodName="WndSizeChanged"
                                     TargetObject="{Binding}" />
            </i:EventTrigger>
        </i:Interaction.Triggers>

        <Grid.ColumnDefinitions>
            <ColumnDefinition  Width="300*" />
            <ColumnDefinition  Width="189*" />
            <ColumnDefinition  Width="720*" />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition  Height="101*" />
            <RowDefinition  Height="372*" />
        </Grid.RowDefinitions>

Basically changed the event that is triggered to be LayoutUpdated. Works like a charm. I am on a time-line so this will have to do. I hope this will help anyone who is in a similar situation as me. Don't forget to call setHeightWidth() in the constructor to set the h and w initially as well.