How to put a default value in a textbox bound to int property wpf c#?

Question

I'm new in xaml and I have some trouble with a textbox bound to an int property.

My property is defined like this :

public Int32 MyInt
    {
        set
        {
            if(MyInt!= value)
            {
                _myInt = value;
                OnSpecificModification();
            }
        }
        get
        {
            return _myInt ;
        }
    }

    private Int32 _myInt = 100;

I have a texbox in my xaml bound to MyInt as follows :

<TextBox PreviewTextInput="NumberValidationTextBox" x:Name="txtDocSteps" x:FieldModifier="private"  Text="{Binding Path=DocSteps, UpdateSourceTrigger=PropertyChanged}"/>

The NumberValidationTextBox is to allow only number in the textbox and is :

private void NumberValidationTextBox(object sender, TextCompositionEventArgs e)
    {
        Regex regex = new Regex("[^0-9]+");
        e.Handled = regex.IsMatch(e.Text);
    }

All works fine when I put a number in the textBox but when I clear it, then I have an error message "The '' value can't be converted." and I understand why : because MyInt is not nullable. I don't want a nullable int because I need a value. I would like that the value defined in my property (100) replace the empty value in my textbox when I move to an another field or when I click on the validate button which the event on the click is :

private void ButtonValidate_Click(object sender, RoutedEventArgs e)
    {
        Plug.MyInt = int.Parse(txtDocSteps.Text);
        Plug.Description = txtUserDescription.Text;
        DialogResult = true;
    }

Thank you for your help with simple explanation to understand how to do.

score 0 · Answer 1 · answered Sep 14 '20 at 16:00

Try adding TargetNullValue in your binding. In your case it should be something like this

<TextBox PreviewTextInput="NumberValidationTextBox" x:Name="txtDocSteps" x:FieldModifier="private"  Text="{Binding Path=DocSteps, UpdateSourceTrigger=PropertyChanged, TargetNullValue=''}"/>

How to put a default value in a textbox bound to int property wpf c#?

1 Answers1