How to access WPF MainWindow Controls from my own .cs file

Question

I am a NOVICE and am very much struggling with what seems should be a very simple task. How do I modify a property of a MainWindow TextBlock, from ano

Answer 1

Basically there are more than 2-3 methods. Given method is quite easier to understand & handle. You can access MainWindow controls by following codes (1),(2),(3),(4).

In File: MainWindow.xaml.cs

  public partial class MainWindow
  {
   internal static MainWindow Main; //(1) Declare object as static
   public MainWindow()
    {
        InitializeComponent();
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
       Main =this; //(2) Defined Main (IMP)
      var AnyClassORWindow=new Class1(); //Initialize another Class
      AnyClassORWindow.ShowValue();
    }
  }

In File: Class1.cs

  internal class Class1 : MainWindow //(3) Inherited
    {
      internal void Display()
        {
           MessageBox.Show(Main.TextBox1.Text); //(4) Access MainWindow Controls by adding 'Main' before it.
         }
     }

Notes:-

1. It's good practice to use code (2) after window LOADED not in CONSTRUCTOR.
2. Code (2) in constructor may leave run-time problems.
3. Another simple method is to use 'ref MainWindow_field' by passing to each class's Constructor OR assign '(MainWindow) Application.Current.MainWindow' to static Main.

Answer 2

You need to create an instance of MainWindow.

But there shouldn't be a reason to do that because it will be done automagically in an WPF app. Unless you have specific reason to do that (which I doubt because of this question and because you say you're a novice).

Answer 3

To extend on what Nathan said, I used a safe cast:

(System.Windows.Application.Current.MainWindow as MainWindow)?.TextBlock1.Text = "Setting Text from My Program";

Note the comments on the answer Nathan gave. This isn't ideal but it works.

Answer 4

Use MVVM pattern to access properties of the control and modify them:

public class Student
{
    public Student()
    {
    }

    public string Name
    {
        get { return "Setting Text from My Program"; }
    }
}

Set the DataContext of the XAML in the code behind:

this.DataContext = new Student();

Bind the Text property to Name:

<TextBlock Text="{Binding Name}"/>

Answer 5

Because nobody else has actually answered the question I'm going to tell you how to achieve what you want, but do listen to the posters who said that in a real application you would use MVVM. However there are times when you need to do what you ask so the code you need is:

((MainWindow)System.Windows.Application.Current.MainWindow).TextBlock1.Text = "Setting Text from My Program";

Answer 6

You can simply achieve this using MVVM. You shouldn't directly access controls in View using its name from another class. You have to use binding properties.

First of all, add a class. This will be your ViewModel. Add your properties to this class which will be binded to your input controls in your View.

Student ViewModel

public class Student
{
    public string Name
    {
        get { return "Setting Text from My Program"; }
    }
}

App.Config

Now you have add to this View Model as a resource in your App.Config file. First, add the name space reference to your app.config where your VM resides. [xmlns:local="clr-namespace:WpfApplication2]. Add your VM class as a resource by specifying your View Model class name (student).

<Application x:Class="WpfApplication2.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             StartupUri="MainWindow.xaml"
             xmlns:local="clr-namespace:WpfApplication2">
    
    <Application.Resources>
        <local:Student x:Key="Student" />
    </Application.Resources>
</Application>

MainWindow.xaml

Set the DataContext with the resource key added to App.config and set the binding to the property defined in the Student View Model.

<Window x:Class="WpfApplication2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        DataContext="{StaticResource Student}"
        Title="MainWindow" Height="350" Width="525">
    
    <Grid>
        <TextBlock Text="{Binding Name}" Height="23" HorizontalAlignment="Left" Margin="127,124,0,0" Name="textBlock1" VerticalAlignment="Top" Width="214" />
    </Grid>
</Window>