ToMouseInfo

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

public class MouseInfo
{
    public double X { get; set; }
    public double Y { get; set; }
    public bool MouseDown { get; set; }
}
public static class MouseMethods
{
    public static MouseInfo ToMouseInfo(this System.Windows.Input.MouseEventArgs e, object sender)
    {
        MouseInfo mi = new MouseInfo();
        Point p = e.GetPosition(sender as UIElement);
        mi.MouseDown = e.GetStylusPoints(sender as UIElement)[0].PressureFactor > 0;
        mi.X = p.X;
        mi.Y = p.Y;
        return mi;
    }
}

MouseInfo mi = e.ToMouseInfo(sender);
if (mi.MouseDown)
{
    mediatest.SetValue<double>(Canvas.LeftProperty, mi.X);
    mediatest.SetValue<double>(Canvas.TopProperty, mi.Y);
}