Resize Form based on ElementHost size

I have a Form(winform) and it contains Elementhost. During run time, i am hosting my WPF Usercontrols to this elementhost. I have used AutoSize = True for elementhost.

Elementhost resizes itself basedon WPF Usercontrol size. But How to resize my form based my ElementHost's size.

Thank you,

Here is the answer:

After setting the ElementHost.Child to WPF User control. I will following function:

public System.Windows.Size GetElementPixelSize(UIElement element) 
    { 
        Matrix transformToDevice; 
        var source = PresentationSource.FromVisual(element);
        if (source != null)
            transformToDevice = source.CompositionTarget.TransformToDevice;
        else     
            using (var Hwndsource = new HwndSource(new HwndSourceParameters()))
                transformToDevice = Hwndsource.CompositionTarget.TransformToDevice;


        if (element.DesiredSize == new System.Windows.Size()) 
            element.Measure(new System.Windows.Size(double.PositiveInfinity, double.PositiveInfinity)); 

        return (System.Windows.Size)transformToDevice.Transform((Vector)element.DesiredSize); 
    } 

Original Method posted at: How do I convert a WPF size to physical pixels?

Now I set the client size from new Size.