How to call the stackpanel children in button click events

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C#

WPF

VS2010

I created a inkcanvas control by creating a custom inkcanvas class .I had taken the instances of this class and add them to stack panel.I dragged the one button control to the mainwindow.In the button click event the instance of stackpanel names (mycanvas1 ) was not visible.how to solve it.

here my code

public partial class MainWindow : Window
   {
       public MainWindow()
       {
           InitializeComponent();
           mycan mycanvas1 = new mycan();
           stkm.Children.Add(mycanvas1);
        }
       

private  void   savebtn_Click(object sender, RoutedEventArgs e )
 {
 
var files = Directory.GetFiles(@"C:\\Users\\SriRampavankumar\\Desktop\\proj").Length;
string fileName = namebox.Text.Substring(0, 3) + -+ ++files + ".txt";
string path2 = System.IO.Path.GetFullPath("C:\\Users\\tom\\Desktop\\proj");
string docPath = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
string var = System.IO.Path.Combine(docPath, path2);
string var1 = System.IO.Path.Combine(var, fileName);
            using (StreamWriter writer = new StreamWriter(var1))
            {
                string var6 = namebox.Text;
                string var7 = "                 ";
                string var8 = agebox.Text;

           }