Develop Reference

WPF passing text from one window to another window

I have a main window and it has a button. When I press the main window button, it will open sub-window. In sub window, I have a text box and when I enter the text and click the add button in sub-window, the text should display on the main window. How do I achieve this? Thanks in advance.

You can create parameterized constructor of MainWindow class and pass value of Textbox from subwindow to main window and in MainWindow you can set content to that label.
Here is the implementation
MainWindow.xmal.cs
public partial class MainWindow : Window
{
public MainWindow ()
{
InitializeComponent();
}
public MainWindow (string text) : this()
{
label.Content = text;
}
private void button_Click (object sender, RoutedEventArgs e)
{
Window1 win1 = new Window1();
win1.Show();
this.Close();
}
}
Here is the code for subWindow i.e. Window1.xaml.cs
public partial class Window1 : Window
{
private string text;
public Window1 ()
{
InitializeComponent();
}
private void button_Click (object sender, RoutedEventArgs e)
{
text = textBox.Text;
MainWindow mainWindow = new MainWindow(text);
mainWindow.Show();
this.Close();
}
}

You can simply modify the constructor of the second window :
public partial class Window1 : Window
{
string text;
public Window1 (string _text)
{
InitializeComponent();
this.text = _text;
}
}

I would add an event to your 'dialog' subwindow which the MainWindow can subscribe to as it instantiates it.
DialogWindow: (subwindow):
public class DialogInputEventArgs : EventArgs
{
public string Input { get; set; }
}
public partial class DialogWindow : Window
{
public event EventHandler<DialogInputEventArgs> InputChanged = delegate { };
private void SubmitInputButton_Click(object sender, RoutedEventArgs e)
{
InputChanged(this, new DialogInputEventArgs() { Input = this._inputTextBox.Text });
}
}
MainWindow:
private void ShowDialogButton_Click(object sender, RoutedEventArgs e)
{
DialogWindow dw = new DialogWindow();
dw.InputChanged += OnDialogInputChanged;
dw.Show();
}
private void OnDialogInputChanged(object sender, DialogInputEventArgs e)
{
// update the MainWindow somehow using e.Input (the text submitted in dialog)
}
If you need this mechanism for multiple windows I would go with something more generic, like a messagebus or observerpattern thing.

I'd suggest you to use CaliburnMicro framwework to achieve easier and better communication between your controls (assuming you are using MVVM pattern). You don't have to implement all features of CaliburnMicro, just EventAggregator to manage sending and handling messages between your controls.

Pass Data from Child Window to MainWindow TextBlock

In this example, MainWindow has a button that opens Window2.
Window2 has a button that writes "Hello, World!" to MainWindow textblock.
Project source: https://www.dropbox.com/s/jegeguhycs1mewu/PassData.zip?dl=0
What is the proper way to pass data from Window2 to MainWindow?
private MainWindow mainwindow;
public MainWindow mainwindow { get; private set; }
public Window MainWindow { get; set; }
private object mainwindow { get; private set; };
private MainWindow mainwindow = ((MainWindow)System.Windows.Application.Current.MainWindow);
this.mainwindow = mainwindow;
MainWindow
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
// Open Window 2
private void buttonWindow2_Click(object sender, RoutedEventArgs e)
{
Window2 window2 = new Window2(this);
window2.Left = Math.Max(this.Left - window2.Width, 0);
window2.Top = Math.Max(this.Top - 0, 0);
window2.ShowDialog();
}
}
Window 2
public partial class Window2 : Window
{
private MainWindow mainwindow;
public Window2(MainWindow mainwindow)
{
InitializeComponent();
this.mainwindow = mainwindow;
}
// Write Message to MainWindow
private void buttonMessage_Click(object sender, RoutedEventArgs e)
{
mainwindow.textBlockMessage.Text = "Hello, world!";
}
}

The 'proper' way usually depends on what your needs and circumstances are. But in general, using a delegate to pass data between windows is a common and standard practice.
Lets say the data you want to pass is a string. In your Main window, you want to create a delegate that lets you pass a string. Then you create an instance of that delegate type and subscribe a method that matches. Then when you open your secondary window, you pass that delegate to your secondary window.
public delegate void DataTransfer(string data);
public partial class MainWindow : Window
{
public DataTransfer transferDelegate;
public MainWindow()
{
InitializeComponent();
transferDelegate += new DataTransfer(DataMethod);
}
public void DataMethod(string data)
{
// Do what you want with your data.
}
private void button1_Click(object sender, EventArgs e)
{
Window2 win = new Window2(transferDelegate);
win.Show();
}
}
Now, when you invoke that delegate in your secondary window, the DataMethod() of your Form1 gets called, and so you can pass information between windows.
Your secondary window implementation should look like this:
public partial class Window2 : Window
{
DataTransfer transferDel;
public Window2(DataTransfer del)
{
InitializeComponent();
transferDel = del;
}
private void button1_Click(object sender, EventArgs e)
{
string data = "Hello, World!"; // Your string data to pass.
transferDel.Invoke(data);
}
}
As you can see, when you invoke the delegate that was passed, it calls the corresponding method in your main program.
One stand out advantage of this method is that you don't need to pass an instance of MainWindow to your Window2, you simply use delegates and subscribed methods to pass data between the two instances of windows.

The answer you're looking for is very implementation-based and depends heavily on what you want Window2 as a class to do.
private MainWindow mainwindow;
This is acceptable.
public MainWindow mainwindow { get; private set; }
This would work but doesn't respect naming conventions because it's a property. Usually you'd use this for encapsulation of a field or for easy access to a computed value.
public Window MainWindow { get; set; }
This is not acceptable in your context because Window does not contain a textBlockMessage.
private object mainwindow { get; private set; };
This also wouldn't work for the same reason as above.
private MainWindow mainwindow = ((MainWindow)System.Windows.Application.Current.MainWindow);
This would work and would even let you not keep a field for the reference to the MainWindow instance in your Window2 instances. Still needs to get that MainWindow everytime you click the button however.
Another interesting way to do what you're doing however is to simply pass the handler to the child windows at instanciation:
MainWindow
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
// Open Window 2
private void buttonWindow2_Click(object sender, RoutedEventArgs e)
{
Window2 window2 = new Window2(); // No need to give a reference to the child window anymore
window2.setClickHandler((obj, ev) => {
textBlockMessage.Text = "Hello, world!"; // Direct access to the textblock.
});
window2.Left = Math.Max(this.Left - window2.Width, 0);
window2.Top = Math.Max(this.Top - 0, 0);
window2.ShowDialog();
}
}
Window2
public partial class Window2 : Window
{
public Window2()
{
InitializeComponent();
}
public void setClickHandler(RoutedEventHandler handler)
{
// The handler is given to the click event.
buttonMessage.Click -= handler;
buttonMessage.Click += handler;
}
}
And with that your Window2 class has no need to know MainWindow.

You could declare a delegate in Window 2 and pass a function that can be executed when the button is pressed in window 2.
public delegate void SendMessage(string Message);
public SendMessage mainWindowDel = null;
Make your constructor that accepts the delegate
public Window2(SendMessage del)
{
mainWindowDel = del;
}
create window 2 by passing a function as the parameter
public void showMessage(string Message)
{
if(!string.IsNullOrWhiteSpace(Message))
textBlockMessage.Text = Message;
}
private void buttonWindow2_Click(object sender, RoutedEventArgs e)
{
// Open Window 2
//Window2 window2 = new Window2(this);
Window2 window2 = new Window2(showMessage);
window2.Left = Math.Max(this.Left - window2.Width, 0);
window2.Top = Math.Max(this.Top - 0, 0);
window2.ShowDialog();
}
call the delegate when they press the button
// Write Message to MainWindow
private void buttonMessage_Click(object sender, RoutedEventArgs e)
{
mainWindowDel("Hello, world!");
}

You could probably set the datacontext of the MainWindow to an object that you could also pass to Window2 when it's created and set it's datacontext to the same object.
In that object could create a string property that could be used in both windows. And if you implement the INotifyPropertyChanged interface both windows would know when that string is updated.

Another Approach
MainWindow
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private bool DisplayText(string displayText)
{
txt_Main.Text = displayText;
return true;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
Window2 win2 = new Window2(DisplayText);
win2.ShowDialog();
}
}
Window2
public partial class Window2 : Window
{
private Func<string, bool> mainWindowMethod;
public Window2(Func<string, bool> displayMethod)
{
InitializeComponent();
this.mainWindowMethod = displayMethod;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
this.mainWindowMethod("Hello World");
}
}

How to access MainWindow's variables from second Window

Is there another way to access MainWindow's public variables than :
MainWindow mainWindow = Application.Current.Windows.OfType<MainWindow>().FirstOrDefault();
mainWindow.variable....
this work fine, but I'm creating a WPF application and integrating a USB Webcam to my project and using this code above to access MainWindow's variables. This causes some problems like program is still running when I close MainWindow and camera won't stop.
Any suggestions?

This is an over simplified example for what i wrote in comments(you really should look at mvvm the example below is not mvvm).
public class SelectedIndexData
{
public int SelectedIndex { get; set; }
}
public partial class MainWindow : Window
{
private readonly SelectedIndexData _selectedIndexData = new SelectedIndexData();
public MainWindow()
{
InitializeComponent();
}
private void ComboBox_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
{
_selectedIndexData.SelectedIndex = ComboBox.SelectedIndex;
}
private void ShowChildWindow(object sender, RoutedEventArgs e)
{
new ChildWindow(_selectedIndexData).Show();
}
}
public partial class ChildWindow : Window
{
private SelectedIndexData _selectedIndexData;
public ChildWindow(SelectedIndexData selectedIndexData)
{
InitializeComponent();
_selectedIndexData = selectedIndexData; // do whatever you want with your data here
}
}

This approach work also if you are developing a dll (you can't tell the same about Application.Current.MainWindow, which is clearer then your attempt anyways)
DependencyObject ucParent = this.Parent;
while (!(ucParent is MainWindow))
{
ucParent = LogicalTreeHelper.GetParent(ucParent);
}
mainview = ucParent as MainWindow;
You can pack this inside a method, save the variables that you need and you shouldn't have problems

To make sure you application shuts down when MainWindow is closed:
public MainWindow()
{
InitializeComponent();
this.Closing += (sender, args) => Application.Current.Shutdown();
}

Passing data between two wpf forms as strings

trying to get data from the main form to form 2. The main form has a textbox
and a button. when the button is pressed it opens form 2 which will display the data entered in the main form as a series of text blocks.
However I cant get the data to transfer between the forms. the code is bellow.
can anyone help or suggest anything I can do differently?
WPF 1 main form:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void btnOpenForm_Click(object sender, RoutedEventArgs e)
{
//btnset: Takes the values contained in the text boxes and updates
//the student class
//properties.
Student.sFname = firstname.Text;
Student.sSname = secondname.Text;
Window1 details = new Window1();
details.Show();
}
WPF 2 code:
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
}
private void details_Load(object sender, EventArgs e)
{
Fname.Text = Student.sFname;
Sname.Text = Student.sSname;
}
private void Close_Click(object sender, RoutedEventArgs e)
{
this.Close();
}
}

There are a number of ways to "pass data" between 2 classes. The easiest way is to expose property or method on Window1 and just set the text you need passed. Another way is to create a constructor on Window1 that takes in the data as parameters. Here is code that demonstrates these approaches.
public class Program
{
public static void Main(string[] args)
{
var c1 = new Class1();
c1.DoStuff();
}
}
public class Class1
{
public void DoStuff()
{
var c = new Class2("stuff");
var c2 = new Class2();
c2.AcceptStuff("stuff2");
c.Print();
c2.Print();
c2.MyData = "stuff3";
c2.Print();
}
}
public class Class2
{
private string _myData;
public Class2()
{
}
public Class2(string myData)
{
_myData = myData;
}
public string MyData
{
set { _myData = value;}
}
public void AcceptStuff(string myData)
{
_myData = myData;
}
public void Print()
{
Console.WriteLine(_myData);
}
}
Prints
stuff
stuff2
stuff3

I assume you have a class in MainWindow like:
`Public class Student
{
public static string sFname;
public static string sSname;
}`
When you click open button you are assigning values to those variable, but if you want to access them in another window mention the window name and then class name.
Check this code if its working?
`public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
}
private void details_Load(object sender, EventArgs e)
{
Fname.Text = MainWindow.Student.sFname;
Sname.Text = Mainwindow.Student.sSname;
}
private void Close_Click(object sender, RoutedEventArgs e)
{
this.Close();
}
}`

Retry button access methods in another class

I have a button in a window that basically does a rerun through some code (retry button)
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
}
private void btnRetry_Click(object sender, RoutedEventArgs e)
{
//TODO retry function
//MainWindow.Connect();
}
private void btnCancel_Click(object sender, RoutedEventArgs e)
{
this.Close();
}
}
I basically want to use the connect method in my main window class. However I can't do that unless it's a public static. However, if I do change Connect() to a public static, all the controls in it require to be static. I'm trying to minimize the amount of static controls I have; can anybody please help with a retry method?

Another solution is to make Window1.btnRetry visible to the parent form
public MainWindow : Window
{
private void ShowWindow1()
{
var window1 = new Window1();
window1.btnRetry.Click += OnRetryClicked;
window1.ShowDialog();
}
private void OnRetryClicked(object sender, EventArgs e)
{
// will be called when window1.btnRetry is clicked.
// retry the connection.
Connect();
}
}

First, you do need to make the method public (or internal) so that Window1 can use the method. However, do not make it static.
Instead, accept an instance of MainWindow in the Window1 constructor, and store it so that you can invoke the Connect() method on it later.
For example:
public partial class Window1 : Window
{
private MainWindow mainWindow;
public Window1(MainWindow mainWindow)
{
if (mainWindow == null) {
throw new ArgumentNullException("mainWindow");
}
this.mainWindow = mainWindow;
InitializeComponent();
}
private void btnRetry_Click(object sender, RoutedEventArgs e)
{
mainWindow.Connect();
}
// ...
}
Then, if constructing the instance from inside of MainWindow change your constructor invocation from new Window1() to new Window1(this).