Question

I have a issue with passing information from one wpf window to another. For some reason when main window is loaded nothing is set in the label, I need to be able to keep the data in a string to use for anything (label not important but shows what I mean)?

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }
    public string MyData { get; set; }

    void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        label1.Content = MyData;

    }

public partial class LoginWindow : Window
{
    public LoginWindow()
    {
        InitializeComponent();
    }
    private void button2_Click(object sender, RoutedEventArgs e)
    {
         string mytext = "blabla";
         MainWindow fromloginwindow = new MainWindow(); 
         fromloginwindow.Mydata = mytext;
    }

Or am I doing this the wrong way round?

EDIT:

Please do not go on a tangent about the label its unimportant I need to be able to get and set a string for use anywhere in the MainWindow. Also the string “mytext” is also irrelevant as obviously I will not be setting the string this way.

Answer 1

It sounds like you are running into an event lifecycle issue; the calls to the Loaded event happen pretty quickly and thus, the chance to set the text has passed. Instead, what you should do is either:

1) Bind the Property to the Label in the XAML

public event PropertyChangedEventHandler PropertyChanged;

public MainWindow()
{
    InitializeComponent();
    DataContext = this;
}

protected string _myData = string.Empty;
public string MyData
{
    get { return _myData; }
    set { _myData = value; NotifyPropertyChanged("MyData"); }
}

protected void NotifyPropertyChanged(string propName)
{
    var methods = PropertyChanged;

    if(methods != null)
       methods(this, new PropertyChangedEventArgs(propName));
}

<Label Content="{Binding MyData}" />

2) Set the control text via another method (or inside the property declaration):

public void SetLabel(string text)
{
    label1.Content = text;
}

protected void button2_Click(object sender, RoutedEventArgs e)
{
     MainWindow x = new MainWindow();
     x.SetLabel("blabla");
}