Erratic behavior of TextBox "TextChanged" event

Question

I have inserted in the GUI a TextBox. It must hold a number between 0 and 1 that represents a lower threshold for accepting a structure name guessed
by the Dice coefficient. I have set a default but the user can edit the threshold. Therefore I have to check the number entered is between 0 and 1.
The TextBox is implemented as follows:

TextBox TextChanged event:
Background="Wheat" FontFamily="Arial Black" FontWeight="Bold" FontSize="20" Width="100" Height="46" Grid.RowSpan="1" TextChanged="DiceTol_TextChanged" TargetUpdated="DiceTol_TargetUpdated" TextInput="DiceTol_TextInput"/>

I developed the code that checks the newly entered number using three different pre-existent TextBox events., namely, "TextChanged", "TargetUpdated", TextInput".
The only event that is triggered is "TextChanged" but it does not work all the times a new number is entered in the TextBox. During the debugging session
first, I erase the default value and then I type in a new value that is on purpose greater than 1 but the "TextChange" event is not triggered. Sometimes it is triggered when I click on a GUI button. The other two events are never triggered.

Here is the code I developed to check the number entered in the TextBox:

private void DiceTol_TextChanged(object sender, TextChangedEventArgs e)
{
if(DiceThreshold < 0 | DiceThreshold > 1)
{
MessageBox.Show("Please, enter a number between 0 and 1", "Warning ", MessageBoxButton.OK, MessageBoxImage.Warning);
DiceThreshold = DiceThresholdDefault;
DiceTol.Text = DiceThresholdDefault.ToString();
emptyEditableStructsListBox();
return;
}
}

I would appreciate your help in fixing the above-illustrated problem.
Thank you

Answer

For the problem of validating the bound data, you could refer to the following code.

MainWindow.xaml.cs:

public partial class MainWindow : Window  
  {  
    public double DiceThreshold { get;set;}= 0.3;  
    public MainWindow()  
    {  
      InitializeComponent();  
      DataContext=this;  
    }  
  }  
public class DoubleRangeRule : ValidationRule  
      {  
        public double Min { get; set; }  
      
        public double Max { get; set; }  
      
        public override ValidationResult Validate(object value,   CultureInfo cultureInfo)  
        {  
          double parameter = 0;  
      
          try  
          {  
            if (((string)value).Length > 0)  
            {  
              parameter = Double.Parse((String)value);  
            }  
          }  
          catch (Exception e)  
          {  
            return new ValidationResult(false, "Illegal characters or "    + e.Message);  
          }  
      
          if ((parameter < this.Min) || (parameter > this.Max))  
          {  
            return new ValidationResult(false,  
                "Please enter value in the range: "  
                + this.Min + " - " + this.Max + ".");  
          }  
          return new ValidationResult(true, null);  
        }  
      }

MainWindow.xaml:

The result:

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Answer

Thank you for the very sophisticated solution.
I wonder whether I can use "Mode=TwoWay" in the binding statement for DiceThreshold. The code needs to use the entered value when it is within the established range.

Answer

@HiuLiu-MSFT
Thank you very much. I got that TextBox working on adopting a simpler solution. Basically, I check the TextBox content when a Button is clicked launching the code stub that uses the TextBox content. If the TextBox numerical content falls outside the range a messageBox alerts the user and the TextBox content is set back to a default value.

However, now I am facing a new challenge and wonder whether the code you sent me could be adapted to my new task.
In MainWindow.XAML I have a ListBox that is used to display a list of strings that can be edited:

** ScrollViewer.VerticalScrollBarVisibility="Visible" ScrollViewer.CanContentScroll="True" ItemsSource="{Binding AutoNames,Mode=TwoWay}" HorizontalAlignment="Left" Width="220" >

**

The code-behind in MainWindow.XAML.cs I populate the above ListBox upon clicking a Button:

public class EditableStructures
{
public int NamInd { get; set; } = new int();
public bool IsAccepted { get; set; } = new bool();
public string StrName { get; set; } = "";
}
```
public static List AutoNames { get; set; } = new List();***
```
PTAccess pt = new PTAccess();
List EditedList = new List();
EditedList = pt.StructuresAutomaticRename(structures);
int j = 1;
foreach (string str in EditedList)
{
AutoNames.Add(new EditableStructures { StrName = str, IsAccepted = false, NamInd = j});
j++;
}
// string DbgList = "" ; // DEBUG PURPOSE
// DbgList = String.Join(" , ", AutoNames.Select(x => x.StrName)); // DEBUG PURPOSE
// MessageBox.Show($"AUTOMATICALLY RENAMED STRUCTURES: {DbgList}"); // DEBUG PURPOSE
//............................ Compare Number of Guessed Structure Names With Number Of Structure Names From Velocity DataBase
// ............................ Alert User If Less Than 50% Structures Could Not Be Guessed
int NumGuessed = 0;
int NumOriginal = 0;
var Guessed = AutoNames.Where(m => !string.IsNullOrWhiteSpace(m.StrName)).ToList();
NumGuessed = Guessed.Count;
NumOriginal = strucNames.Count;
MessageBox.Show($" {NumGuessed} structures automatically renamed out of {NumOriginal} patient structures ", "Is this patient belonging to this trial? ", MessageBoxButton.OK, MessageBoxImage.Information);
UpdateAutoStrucNames();***

*public void UpdateAutoStrucNames()
{
EditableStructs.ItemsSource = (System.Collections.IEnumerable)AutoNames;
}
``***

Some of the ListBox items contain strings that have been "guessed" through the dice coefficient. The code knows the indexes of the items containing "guessed" strings.
My questions:
How can I draw the user's attention to such ListBox elements? Maybe changing their background color or showing the red "!" symbol as you implemented, or some other way.

I would appreciate some help.
Thank you in advance.

Erratic behavior of TextBox "TextChanged" event

3 answers