Accessing control in code behind file

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WPF

<listview>
<listview.view>
<gridview>
<gridviewcolumn header="Field 1 (User ID)" width="110">
<gridviewcolumn.celltemplate>
<datatemplate>

<textblock x:name="BindingText" verticalalignment="Center" xmlns:x="#unknown">					
<passwordbox x:name="MyPasswordBox" password="{Binding Text, Mode=TwoWay, ElementName=MyTextBox}" />

<textbox x:name="MyTextBox" text="{Binding Password, Mode=TwoWay, ElementName=MyPasswordBox}" visibility="Collapsed" />

<checkbox x:name="ShowPasswordCharsCheckBox" content="Show password" checked="ShowPasswordCharsCheckBox_Checked" unchecked="ShowPasswordCharsCheckBox_Unchecked" />
</textblock>
</datatemplate>
                        
</gridviewcolumn.celltemplate>
</gridviewcolumn>
</gridview>
</listview.view>
</listview>

how do i access TextBox & PasswordBox in code behind file



like below one

private void ShowPasswordCharsCheckBox_Checked(object sender, RoutedEventArgs e)
       {
           MyPasswordBox.Visibility = System.Windows.Visibility.Collapsed;
          MyTextBox.Visibility = System.Windows.Visibility.Visible;
           MyTextBox.Focus();
       }

       private void ShowPasswordCharsCheckBox_Unchecked(object sender, RoutedEventArgs e)
       {
           MyPasswordBox.Visibility = System.Windows.Visibility.Visible;
           MyTextBox.Visibility = System.Windows.Visibility.Collapsed;
           MyPasswordBox.Focus();
       }

here it gives me an error that
MyPasswordBox Doesn't exist in the current context
MyTextBox Doesn't exist in the current context