Open a WPF Popup with a button

Question

I'm trying to open a Popup with a button and have implemented a basic ICommand. The button is binded to the ICommand OpenPopupCommand while the Popup IsOpen attribute is binded to the "IsOpen" OnPropertyChanged. My thought process was to bind the Popup.IsOpen attribute to the ICommand as well to have IT trigger the OnPropertyChange but couldn't get it to work. I think I'm close but can't figure it out. Here is the code I have so far:

    #region ICommand Members

    private ICommand _openPopupCommand;
    public ICommand OpenPopupCommand
    {
        get
        {
            if (_openPopupCommand == null)
                _openPopupCommand = new RelayCommand(param => OpenPopupExecute(param));
            return _openPopupCommand;
        }
        set 
        {
            _openPopupCommand = value;
        }
    }

    #endregion

    #region Methods

    public void OpenPopupExecute(object parameter)
    {
        parameter = true;
        OnPropertyChanged("IsOpen");
    }

    #endregion

Button that "pops up" the Popup and the Popup XAML:

<Popup x:Name="FieldsPopup" Placement="Center" Width="400" Height="250" IsOpen="{Binding IsOpen}">
                    <StackPanel>
                        <TextBlock Background="LightBlue" HorizontalAlignment="Center" VerticalAlignment="Center" Height="250" Width="350" TextAlignment="Center" >This is a popup</TextBlock>
                    </StackPanel>
                </Popup>
<Button Name="button_PatientIdentifierList" Width="23" Height="23" Grid.Column="2" Foreground="Black" Background="#FFCDCDCD" BorderBrush="#FF707070" Margin="3.4,4,4,0" VerticalAlignment="Top" Command="{Binding OpenPopupCommand}"/>

Solution

You're raising the PropertyChange notification, but I don't see you actually changing the property anywhere.

Unless I'm mistaken, this code here takes the CommandParameter (called parameter here) and sets it to true

public void OpenPopupExecute(object parameter)
{
    parameter = true;
    OnPropertyChanged("IsOpen");
}

However in your XAML the Button.CommandParameter isn't bound to anything

<Button Command="{Binding OpenPopupCommand}"/>

So I suspect that parameter is just null, and is not actually doing anything here.

What you seem to be missing is the actual IsOpen property definition, and setting it to true in your command's Execute code :

private bool _isOpen;
public bool IsOpen
{
    get
    {
        return _isOpen;
    }
    set 
    {
        _isOpen = value;
        OnPropertyChanged("IsOpen");
    }
}

public void OpenPopupExecute(object parameter)
{
    IsOpen = true; // Will call OnPropertyChanged in setter
}

As a side note, I really don't like WPF's default PopupControl, and have a custom UserControl version of it on my blog if you ever decide you hate WPF's default PopupControl too :)

Comments

[Admin]

parameter is an argument variable of the OpenPopupExecute mMethod, and thus local to the method. Assigning a different value to that variable does not have any effect outside of that method... Thus, your musings about CommandParameter are unfounded. Anyway, i am just nitpicking. The other and more important part about IsOpen is ofcourse sound and true. (Okay, some more nitpicking: It would be nice to safeguard the setter so that the event is not raised if the property is set to a value it already has :) )

[jarheadWill]

@Rachel I appreciate the customer UserControl version of your PopupControl! I'm a bit of a rookie (if you couldn't tell) and likely get lost but I'll take a look! Also, I had something similar to the solution you posted with the only difference being the OpenPopupExectue body not having the IsOpen = true; part. I made the change and we have success! Thank you all for the help!

[Stígandr]

@Rachel I agree the default popup control is not very nice to work with, and I've done the same as you. It's not part of the visual tree, and tons of issues with the control. Particulary when it comes to XBAP applications...