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Validate Input of UserControl in Window WPF

Currently I have a UserControl contained within a window. The UserControl is made up of two text boxes. The UserControl is an element in my MainWindow. Outside the scope of my UserControl is my submit button in my window. I would like to enable and disable the button whenever the boxes text contents are not null or null.
UserControl XAML code:
<UserControl x:Class="myClass.myUserControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d">
<StackPanel Background="White">
<DockPanel>
<Label x:Name="lbl1" Content="First Box:"/>
<TextBox x:Name="txtbox1"/>
<Label x:Name="lbl1" Content="Second Box:"/>
<TextBox x:Name="txtbox2"/>
</DockPanel>
</StackPanel>
</UserControl>
View Model:
using System;
namespace myClass {
partial class UserControlViewModel: ViewModelBase {
private bool _validInput;
public UserControlViewModel() {
validInput = false;
}
public object validInput {
get { return _validInput; }
set {
_validInput = value;
OnPropertyChanged("validInput");
}
}
}
ViewModelBase:
using System.ComponentModel;
namespace myClass {
class ViewModelBase : INotifyPropertyChanged {
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propertyName) {
var handler = PropertyChanged;
if (handler != null) {
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
My issue is deciding on how to handle this validation, my button's isEnabled property is currently bounded to the validInput boolean of the view model. However, the contents of the user control are not accessible in my window as I have abstracted it as a separate userControl item (I plan on having different user controls available to be shown in the window).
MainWindow XAML:
<Window x:Class="myClass.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:uc="clr-namespace:myClass"
Title="MainWindow" Height="356" Width="699" ResizeMode="NoResize" WindowStartupLocation="CenterScreen">
<Window.DataContext>
<uc:UserControlViewModel/>
</Window.DataContext>
<Grid>
<UserControl x:Name="usrControl"/>
<Button x:Name="btn" Content="Create" Click="btn_Click" IsEnabled = "{Binding validInput}"/>
</Grid>
</Window>
MainWindow C#:
using System;
using System.Windows;
using System.Windows.Controls;
namespace myClass {
public partial class MainWindow: Window {
UserControlViewModel view;
public MainWindow() {
InitializeComponent();
view = new UserControlViewModel();
DataContext = view;
}
}
I need to be able to check the contents of the text boxes in the UserControl from the MainWindow as my view is in the MainWindow, however the contents are inaccessible to me and it doesn't make sense to have the view in the UserControl. How should I go about solving this?

I've created a similar project. Mainly to do this, validate through your c# code. Basically
(i don't remember id its .content or .text to get the value)
if(txtbox1.Content == ---or--- (textbox1.Content).Equals(Whatever)){
----code---
}
else{
MessageBox.Show("Error")
}
instead of 'disabling' the button (which I don't think you can do) just make it so if invalid, the user knows or just doesn't do anything.
unrelated: if you are wanting a certain input instead of a blank textbox input, you could use this code to give a base if user leaves empty
private void txtbox1_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
if (txtbox1.Text.Equals("your origional text"))
{
Name_Text.Text = "";
}
}
private void txtbox1_LostKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
if (Name_Text.Text.Equals(""))
{
Name_Text.Text = "your origional text";
}
}
hope this helps

C# Prism : Setting ViewModel property from a controller (MVVM)

The ViewModel:
public class ConnectionStatusViewModel : BindableBase
{
private string _txtConn;
public string TextConn
{
get { return _txtConn; }
set { SetProperty(ref _txtConn, value); }
}
}
The XAML:
<UserControl x:Class="k7Bot.Login.Views.ConnectionStatus"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:prism="http://www.codeplex.com/prism"
prism:ViewModelLocator.AutoWireViewModel="True" Width="300">
<Grid x:Name="LayoutRoot">
<Label Grid.Row="1" Margin="10,0,10,0">connected:</Label>
<TextBlock Text="{Binding TextConn}" Grid.Row="1" Grid.Column="1" Margin="10,0,10,0" Height="22" />
</Grid>
</UserControl>
The View:
public partial class ConnectionStatus : UserControl
{
public ConnectionStatus()
{
InitializeComponent();
}
}
In another module, I have an event listener, that eventually runs this code:
ConnectionStatusViewModel viewModel = _connectionView.DataContext as ConnectionStatusViewModel;
if (viewModel != null)
{
viewModel.TextConn = "Testing 123";
}
The code runs but the TextConn is updated and does not display in the UI

Are you sure TextConn does not update? Because it can update but the display could not change. You should implement the INotifyPropertyChanged interface and after you make any changes to TextConn call the implemented OnPropertyChanged("TextConn"); or whatever you name the function. This will tell the UI that the value has changed and it needs to update.

The UserControl's DataContext gets its value when the UC is initialized. Then you get a copy of the DataContext, cast it to a view model object, and change the property. I don't believe that the UC gets its original DataContext updated in this scenario.
Probably you need to use a message mediator to communicated changes between different modules.

After some troubleshooting, this code works, the issue was that I was running this code:
ConnectionStatusViewModel viewModel = _connectionView.DataContext as ConnectionStatusViewModel;
if (viewModel != null)
{
viewModel.TextConn = "Testing 123";
}
before the view was actually activated. Silly, but maybe it will help someone down the line.

WPF MVVM switch usercontrols

I am new to MVVM and WPF but I know what's going on in MVVM. I have a problem with switching between user controls in mainwindow. In my app I have:
MainWindow.xaml with log and 2 links: Show all and Create new. Of course I have ViewModel for it. I have 2 more UserControls: ShowAll and Create with ViewModels and all logic in it (adding data etc). How can I show create form when I click link Create new or show all when I click ShowAll?
In windowForms I just hide UC, buto here is no code behind :)
My MainWindow.xaml:
<Window x:Class="Test.Views.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="300" Width="300">
<Grid>
<StackPanel>
<TextBox Text="{Binding Name}"/>
<Button Content="Change" Command="{Binding ChangeCommand}"/>
</StackPanel>
</Grid>
</Window>
My MainWindowViewModel:
class MainWindowViewModel : BaseViewModel
{
private Person _person;
private BaseCommand _changeCommand;
public MainWindowViewModel()
{
_person = new Person();
}
public string Name
{
get
{
return _person.Name;
}
set
{
if (_person.Name != value)
_person.Name = value;
OnPropertyChanged(() => Name);
}
}
public ICommand ChangeCommand
{
get
{
if (_changeCommand == null)
_changeCommand = new BaseCommand(() => change());
return _changeCommand;
}
}
private void change()
{
_person = new Person();
Name = _person.Imie;
}
}
In Create and ShowAll there is no code. In xaml only a label, VM is empty. Just for test.
Thank's for help!

You can use a ContentControl to display a specific DataTemplate based on the type of ViewModel that is bound to the ContentControl.
http://www.japf.fr/2009/03/thinking-with-mvvm-data-templates-contentcontrol/
The command that is bound to the ShowAll button can simply change a property on your main ViewModel which is what is bound to your content control.

Creating a single controller for multiple WPF Pages

I'm very new to WPF and a beginner in C#.NET. I'm currently making an application where there will be many pages and the trigger to change the page is hand gesture using Kinect SDK (the trigger method is not relevant for this question). Normally when a WPF file is created, there will be a similarly named .cs file attached to it, which acts somewhat like a controller. However, I need multiple WPF files/pages to be controlled only by a single controller .cs file. How do I achieve that? Thanks for viewing my question and your answer will be very appreciated :)

You probably want to write a class that contains your 'controller' code and reference it from your WPF UserControls / Pages.
In a new file:
public class MyController
{
public void DoThings(object parameter)
{
// stuff you want to do
}
}
and then inside your UserControl code-behind class:
public partial class MyWpfControl : UserControl
{
private MyController controller;
public MyWpfControl
{
this.controller = new MyController();
}
}
and finally, tie your events back to the controller's method:
private void OnGesture(object sender, EventArgs e)
{
// call the method on the controller, and pass whatever parameters you need...
this.controller.DoThings(e);
}

The code behind is really part of the view and isn't really analogous to a controller and generally there shouldn't be much code in them. Typically you would want most of your logic between your "View Model" which serves as an abstraction of the view and "Model" which serves as an abstraction of the business logic that your UI is interacting with.
In this light what I think you really want is a View Model(VM) that controls multiple views. This is a fairly typical scenario and the preferred method (IMO anyway) is to have a hierarchical view model that has a top level the application model and a number of sub VMs that represent different components within your UI, though you can bind everything to your top level VM if you really want to.
To do this we would first define our view model like so
public interface IGestureSink
{
void DoGesture();
}
public class MyControlVM : INotifyPropertyChanged, IGestureSink
{
public event PropertyChangedEventHandler PropertyChanged = delegate { };
private ApplicationVM parent;
public MyControlVM(ApplicationVM parent)
{
this.Name = "my user control";
this.parent = parent;
parent.PropertyChanged += (s, o) => PropertyChanged(this, new PropertyChangedEventArgs("Visible"));
}
public String Name { get; set; }
public bool Visible { get { return parent.ControlVisible; } }
public void DoGesture()
{
parent.DoGesture();
}
}
public class ApplicationVM : INotifyPropertyChanged, IGestureSink
{
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public ApplicationVM()
{
this.ControlVM = new MyControlVM(this);
this.ControlVisible = false;
}
public MyControlVM ControlVM { get; private set; }
public bool ControlVisible {get; set;}
public void DoGesture()
{
this.ControlVisible = !this.ControlVisible;
PropertyChanged(this, new PropertyChangedEventArgs("ControlVisible"));
}
}
and then all we need to do is to build a user control
<UserControl x:Class="WpfApplication2.MyControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Grid Background="LightBlue">
<Label Content="{Binding Name}"/>
</Grid>
</UserControl>
and page
<Window xmlns:my="clr-namespace:WpfApplication2" x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />
</Window.Resources>
<Grid>
<my:MyControl Width="200" Height="200" x:Name="myUserControl" DataContext="{Binding ControlVM}" Visibility="{Binding Visible,Converter={StaticResource BooleanToVisibilityConverter}}"/>
<Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="222,262,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" />
</Grid>
</Window>
That use it. The only thing that we need in our code behind is a constructor that sets up the page VM and wiring from our button to the view model.
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new ApplicationVM();
}
private void button1_Click(object sender, RoutedEventArgs e)
{
((IGestureSink)(this.DataContext)).DoGesture();
}
}
If you wanted to use a monolithic view model instead you would use this Instead of binding the DataContext to ControlVM:
<my:MyControl Width="200" Height="200" x:Name="myUserControl" DataContext="{Binding DataContext}" Visibility="{Binding ControlVisible,Converter={StaticResource BooleanToVisibilityConverter}}"/>

MVC through C# / WPF: how to notify view?

I'm doing a very simple implementation of the MVC pattern in C# with a WPF interface.
I have a model that's keeping the state. I want to be able to notify the view form the model whenever anything about the state changes, so that the view can update itself accordingly.
What's the simplest best practice for doing this in WPF? I know there's such a thing as a PropertyChanged event, is that what I'm looking for or is that too specific for my situation?
Thanks!

Yes. Implement the interface INotifyPropertyChanged.
An example:
MainWindow.xaml
<Window x:Class="INotifyChangedDemo.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<Label Content="{Binding HitCount}"></Label>
<Button Grid.Row="1" Click="Button_Click">
Hit
</Button>
</Grid>
MainWindow.xaml.cs
namespace INotifyChangedDemo
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
private MainViewModel _viewModel = new MainViewModel();
public MainWindow()
{
InitializeComponent();
DataContext = _viewModel;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
_viewModel.HitCount = _viewModel.HitCount + 1;
}
}
}
MainViewModel.cs
namespace INotifyChangedDemo
{
public class MainViewModel : INotifyPropertyChanged
{
private int _hitCount;
public int HitCount
{
get
{
return _hitCount;
}
set
{
if (_hitCount == value)
return;
_hitCount = value;
// Notify the listeners that Time property has been changed
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("HitCount"));
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
}
For better implementation of INotifyChangedProperty, please refer to this thread: Automatically INotifyPropertyChanged.
If you wanna know more about the MVVM pattern, please see here: http://msdn.microsoft.com/en-us/magazine/dd419663.aspx

If your view binds to a property declared in your model, and your property raises the PropertyChanged event whenever it is changed, then your view will automatically be updated with the new value. For instance, your view might declare the following:
<TextBlock Text="{Binding Name}" />
And in your model you would have:
string _name;
public string Name
{
get
{
return _name;
}
set
{
_name = value;
RaisePropertyChanged("Name");
}
}
This assumes that you are using some framework / helper that provides the RaisePropertyChanged method. I am taking this example from the Galasoft MVVM framework, but I assume that exactly the same principal applies in MVC.
Hope this helps.