Question

So it’s like this, I have a wpf binding

<TextBox
        Name="txtRackNo"
        Grid.Column="5"
        Grid.ColumnSpan="7"
        Grid.Row="4"
        Grid.RowSpan="1"
        Style="{StaticResource ResourceKey=styleValidationTextBox}"
        Text="{Binding Path=rack_no, Mode=TwoWay, ValidatesOnDataErrors=True, UpdateSourceTrigger=LostFocus}">
</TextBox>

If I implement IDataErrorInfo and have property directly in my viewmodel, then it works, it shows the tooltip and red validation box.
If I implement IDataErrorInfo in a class that is a property of my viewmodel, the style creates the tooltip, but the red error box does not show up. I am sure that my style is working, it is just that if I change this line

Text="{Binding Path=rack_no, Mode=TwoWay, ...}" 

to use my datatype “RACK”

Text="{Binding Path=rack.rack_no, Mode=TwoWay, ...}"

private Rack _rack;
public Rack rack
{
    get { return _rack; }
    set
    {
        _rack = value;
        createPropertyObserver();
        base.RaisePropertyChanged("rack");
    }
}

then it only shows the tooltip and not the red validation error box.

EDIT: Here is more code, maybe this will help someone to understand my question better?

class Rack : ObservableObject, IDataErrorInfo
{
    public String _rack_no;
    public String rack_no
{
         get { return _rack_no; }
    set
    {
    if (value != null)
    {
        _rack_no = value;
        base.RaisePropertyChanged("rack_no");
    }
    }
}

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

    public String this[String propertyName]
    {
        get
        {
            String result = String.Empty;
            propertyName = propertyName ?? String.Empty;
            if (propertyName == String.Empty || propertyName == "dc_name")
            {
                if (String.IsNullOrEmpty(this.dc_name))
                {
                    result += "Datacenter name is mandatory." + Environment.NewLine;
                }
            }

            if (propertyName == String.Empty || propertyName == "rack_no")
            {
                if (String.IsNullOrEmpty(this.rack_no) || this.rack_no.Length > 5)
                {
                    result += "Rack number is mandatory and must be 5 letters or less."
                        + Environment.NewLine;
                }
            }
            Debug.WriteLine(result);
            return result.TrimEnd();
        }
    }

Then here is part of my viewmodel:

              private Rack _rack;
    public Rack rack
    {
        get { return _rack; }
        set
        {
            _rack = value;
            createPropertyObserver();
            base.RaisePropertyChanged("rack");
        }
    }

If in my view, I bind the text box to rack.rack_no, if there is a validation error, the tooltip works and shows the proper error message. However, it does not change the textbox to use the validationstyle.

If I create the same property (rack_no) and implement idataerrorinfo in my viewmodel, then I bind to this instead, it works perfect.

I just want to know if I am doing something wrong here, like is this not a valid binding for validation? is there a way to allow me to continue to bind to the rack.rack_no class and use validation?

Answer 1

Scrapped this idea and instead decided to use the method given in the below:
http://www.codeproject.com/Articles/15239/Validation-in-Windows-Presentation-Foundation
and
http://www.codeproject.com/Articles/97564/Attributes-based-Validation-in-a-WPF-MVVM-Applicat

This use idataerrorinfo in combination with System.ComponentModel.DataAnnotations; to perform validation. I also changed my validation style to manually create the red box which seems to have fixed the problem with using the default validation style while validating databindings which are bound to child objects.