Erratic behavior of TextBox "TextChanged" event

[mauede]

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 x:Name="DiceTol" Grid.Column="1" HorizontalAlignment="Left" Margin="655,0,0,0" Grid.Row="1" Text="{Binding DiceThreshold , Mode=TwoWay}" VerticalAlignment="Bottom"
                          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

 

[Skydiver]

Not a direct answer for your question, but it seems that your objective is to implement validation. So why not use the existing infrastructure for it:

How to: Implement Binding Validation - WPF

Learn how to using binding validation to provide visual feedback to the user when an invalid value is entered in Windows Presentation Foundation (WPF).

docs.microsoft.com

 

[Skydiver]

A more accessible article regarding validation in WPF:

Data validation in WPF

A common requirement for any user interface application that accepts user input is to validate the entered information to ensure that it has the expected format and type for the back-end to be able…

blog.magnusmontin.net

 

[mauede]

Not a direct answer for your question, but it seems that your objective is to implement validation. So why not use the existing infrastructure for it:

How to: Implement Binding Validation - WPF

Learn how to using binding validation to provide visual feedback to the user when an invalid value is entered in Windows Presentation Foundation (WPF).

docs.microsoft.com

Sorry. It does not work for me. The property "Source" does not belong to TextBox.
I inserted the TextBox.Text element but still "Source" is not found. If I hover on it I can see a message stating that a namespace is missing.

 

[Skydiver]

Perhaps I'm missing something. Source is a property of the Binding, not of the TextBox if you look closely at the sample code in that MSDN link.

 

[mauede]

I think I have to get my head around how classes properties are accessed.
If I define the following property in the MainWindow class that is part of namespace "WPFUI" :

 private double _diceThreshold = 0.33;
        public double DiceThresholdDefault = 0.33;
        public double DiceThreshold
        {
            get { return _diceThreshold; }
            set
            {
                if (value < 0 || value > 1)
                    throw new ArgumentOutOfRangeException("value");
                _diceThreshold = value;
            }
        }

Then the compiler does not resolve the name "DiceThreshold" used inside the other class "PTAccess" which is part of the same namespace "WPFUI".
I don't get it as "DiceThreshold" is a PUBLIC property.....????
How am I supposed to use the properties defined in MainWindow class from another external class (PTAccess) given that everything belongs to the same namespace?
Shall I create an instance of MainWindow from class PTAceess to get a handle on properties defined inside MainWindow?

I moved the above definition of property "DiceThreshold" inside PTAccess class and accessed its fields from inside MainWindow class by creating a new instance of the class as follows:

PTAccess pt = new PTAccess();
            if (pt.DiceThreshold < 0 | pt.DiceThreshold > 1)

The compiler does not complain but at runtime, I can type inside the textbox whatever number I want and nothing happens.
The TextBox is defined as follows:

 <TextBox x:Name="DiceTol" Grid.Column="1" HorizontalAlignment="Left" Margin="655,0,0,0" Grid.Row="1"  VerticalAlignment="Bottom"
                          Background="Wheat"  FontFamily="Arial Black" FontWeight="Bold" FontSize="20" Width="100" Height="46" Grid.RowSpan="1"
                            TextChanged="DiceTol_TextChanged" >
            <TextBox.Text>
                <Binding  Path="DiceThreshold, Mode=TwoWay" UpdateSourceTrigger="PropertyChanged"  ValidatesOnDataErrors="True"  />
            </TextBox.Text>
       </TextBox>

I reckon the MainWindow.XAML controls look for corresponding property names inside the class MainWindow and discard all definitions in any other class that is part of the same solution/program.
I started to appreciate the MVVM scheme that I refused out of lack of familiarity.