Adding a textbox on button click in c# wpf

Your XAML file should look like this (add "button_Click" event handler to the button):

<StackPanel x:Name="tbPanel">
...
</StackPanel>

<Button Content="Add Metric" Width="100" HorizontalAlignment="Center" Height="30" Grid.Row="1" Grid.Column="0" Click="button_Click"/>

And in your code behind file add method

private void button1_Click(object sender, RoutedEventArgs e)
{
  var newTextBox = new TextBox();
  // here set new textbox parameters
  tbPanel.Children.Add(newTextBox);
}

I would put the textboxes in a StackPanelPanel(container) and on the buttons click-event build up a new textbox and add it add the end of the panel.

Pseudo:

var textBox = new TextBox();
textBox.Width = 100;
...

this.ThePanel.Controls.Add(textBox);

If code-behind then I would recommend adding all controls from code-behind and store them in a array of some sort (maybe Queue or List) so you easely can get the values from them later.

Here is what I do when writing MVVM application.

Create class that will handle your commands (this is just a quick sample):

class CommandHandler:ICommand
{
    private Action action;
    private Func<bool> isEnabled;

    public CommandHandler(Action _action, Func<bool> _isEnabled)
    {
        action = _action;
        isEnabled = _isEnabled;
    }

    public bool CanExecute(object parameter)
    {
        return isEnabled();
    }

    public event EventHandler CanExecuteChanged;

    public void Execute(object parameter)
    {
        action();
    }
}

Now under you ViewModel, you have to create tow things: 1) Create method that you will call with your button click like the following

Public void ButtonWasClicked()
{
   //do something here
}

2) Create actual command

    private ICommand _cmd_MyCommand;
    public ICommand cmd_MyCommand
    {
        get { return _cmd_MyCommand ?? new CommandHandler(ButtonWasClicked, new Func<bool>(() => true)); }
    }

and finally under your View (WPF window) you can bind the command like this:

<Button  Command="{Binding cmd_MyCommand}">

Obviously, there are also other methods how you can use with Commands in WPF (e.g. some folks might suggest RelayCommand). This may seem a bit strange in the beginning (why so much trouble for a simple button click), but you will get into it really quickly once you start using them.

Here is some nice video on MVVM commands that I used in the past as well: http://www.youtube.com/watch?v=EpGvqVtSYjs

Good luck!