How to save WPF textbox value to variable

Question

Im trying to make a WPF based program that will read the textbox input (user input) from a usercontrol and save it as a object proprety. The usercontrol is added to MainWindow. From MainWindow, you have a button which displays a message box with the textbox value. I'm not sure how to connect it all.

Error = CS0103 The name 'minJpValue' does not exist in the current context WpfApp1

Please help

1. (Usercontrol .xaml code)

   <TextBox x:Name="minJpValue"/>
   

2. (Custom class)

   public class jpData 
   {
       public double minJpValue
       {
           get { return minJpValue; }
           set { minJpValue = value; }
       }
   }
   

3. (MainWindow .cs code)

   private void clickclick(object sender, RoutedEventArgs e)
   {
       MessageBox.Show(minJpValue);
   }
   

Answer 1

The issue can be easily fixed using the MVVM Patterns, The code for the usercontrol will be similar to this

<Grid Background="Red">
    <TextBox x:Name="minJpValue" Text="{Binding Path=minJpValue}" />
</Grid>

Create new ViewModel for the MainWindow as follows

public class MainWindowViewModel : INotifyPropertyChanged
{
    /// <summary>
    /// Property Changed Event Handler
    /// </summary>
    public event PropertyChangedEventHandler PropertyChanged;

    // Create the OnPropertyChanged method to raise the event
    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }
   private String _minJpValue;
    public String minJpValue {
        get { return _minJpValue; }
        set {
            _minJpValue = value;
            OnPropertyChanged(nameof(minJpValue));
        }
    }

}

Add the usercontrol into your MainWindow view and in the codebehind set the datacontext to the ViewModel as follows

 public MainWindowViewModel CurrentModel = new MainWindowViewModel();

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

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        MessageBox.Show(CurrentModel.minJpValue);
    }

This can solve your current problem. Please see that its working as per expected.

Answer 2

For this quick fix use:

 MessageBox.Show(minJpValue.Text);

---

But a better way would be to store the value on a VM (View Model) and bind the control to it using the MVVM pattern. I provide a basic example on

Xaml: ViewModel Main Page Instantiation and Loading Strategy for Easier Binding

Answer 3

Ok let's Understand wt have u done wrong.

<TextBox Name="minJpValue"/>

This line of will Create an object for TextBox and the object will be referred with ur name minJpValue as u mentioned this will be inside another Usercontrol object and u r try to minJpValue in MainWindow how does it even know that something like minJpValue this exists

So Here is the answer:

objjpData.minJpValue = minJpValue.Text;//Inside user control when ever u change the `minJpValue` u need to set it too bjjpData.minJpValue

pass this objjpData to mainwindow or where u wanna acesses then

MessageBox.Show(objjpData.minJpValue);

Option 2: MessageBox.Show(UserControlObject.minJpValue.Text);

And PS: Check MVVM once