WPF validation not working as expected

Question

I have a TextBox on WPF that I want to validate. I'm using Binding to validate it:

<TextBox Text="{Binding Path=Name, UpdateSourceTrigger=Explicit}" TabIndex="0" LostFocus="TextBox_OnLostFocus">
</TextBox>

The LostFocus event:

private void TextBox_OnLostFocus(object sender, RoutedEventArgs e)
{
    ((Control) sender).GetBindingExpression(TextBox.TextProperty);
}

Code behind the validation:

public string Name
{
    get { return _name; }
    set
    {
        _name = value;
        this.OnPropertyChanged(new PropertyChangedEventArgs("Name"));

    }
}

public string Error { get { return this[null]; } }

public string this[string columnName]
{
    get
    {
        string result = string.Empty;
        columnName = columnName ?? string.Empty;
        if (columnName == string.Empty || columnName == "Name")
        {
            if (string.IsNullOrEmpty(this.Name))
            {
                result += Properties.Resources.ValidationName + Environment.NewLine;
            }
        }
        return result.TrimEnd();
    }
}

I have some questions:

1. When I first load my Window, my control is surrounded by a red square (the validation one), but I want it to appear only when I fire it (on the Explicit side).

2. How can I know if all my fields have been validated? I mean, when I press a button I only need to know how to know if all controls have been validated.

NOTE: I do have this context on the Constructor:

User u = new User();
DataContext = u;

score 1 · Accepted Answer · edited May 23 '17 at 10:30

1

Your first question may be answered here Did you try setting the binding mode to Default?
The Validation.HasError Attached Property will tell you if any binding on a particular UI Element has any binding validation errors. Use that on every control you need to have validated. Try that first. If you are using a pattern like MVVM, you could create properties on your VM to bind to the Validation.HasError properties.

edited May 23 '17 at 10:30

Community

1
1

answered Feb 06 '13 at 13:03

Szymon Rozga

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The `Validation.HasError` did solve the second question, but the first one still remains. When I load my textbox it still remains red... – Sonhja Feb 06 '13 at 14:37
Propably because your property is invalid already. I consider it good practice that it does that. Why is an empty filename ok when you open the window, but not after you added one character and then deleted it? – dowhilefor Feb 06 '13 at 14:41
I agree you, @dowhilefor, but in part. On first load, I don't see so practical that it's red, as it's not obvious, as the user didn't wrote anything yet. So I'm not sure on how to avoid that (only for visual practces). On the otherhand, I misunderstood siz too. I changed Mode to Default, but it still remains red. – Sonhja Feb 06 '13 at 14:45

score 0 · Answer 2 · edited Dec 31 '16 at 14:35

Actually, my problem had something to do with the class I used to validate. The class does this:

public ErrorProvider()
{
    this.DataContextChanged += new DependencyPropertyChangedEventHandler(ErrorProvider_DataContextChanged);
    this.Loaded += new RoutedEventHandler(ErrorProvider_Loaded);
}

So whenever it first loads, it suscribes to the Load event and then it launches this:

private void ErrorProvider_Loaded(object sender, RoutedEventArgs e)
{
    Validate();
}

so I commented it, and launched the Validate() method when needed....

WPF validation not working as expected

2 Answers2