Screen Validation With Data Annotations on Button Click in WPF

Question

I'm having a WPF Form contains a Single Property "PersonName". I wish to raise error on NULL OR EMPTY. I got a solution from Data Annotations, I refereed the tutorial http://www.c-sharpcorner.com/uploadfile/20c06b/screen-validation-with-data-annotations-in-wpf/

My XAML is

<TextBox Text="{Binding PersonName, UpdateSourceTrigger=PropertyChanged,
 NotifyOnValidationError=True, ValidatesOnDataErrors=True}" />

<Button Content="Save" IsDefault="True" Command="{Binding SaveCommand}"
 IsEnabled="{Binding }" Width="150" Height="40"/>

I can able to see the error only on onPropertyChange event. If I directly hit the button without touching the TextBox means, I can't able to see the Error. How could I trigger the same functionality on Button Click.

My Requirement is PersonName Should not be NULL or EMPTY, If the Property is NULL or EMPTY, then I need to disabled the Button, based on IDataErrorInfo not by Property.Length

Initial, we don't apply any validation. Once wrong data entry or without value hitting Button, then I need a validation.

Answer 1

Use IDataErrorInfo interface and inplement it as below like

public class ABC : IDataErrorInfo
{
    private string _PersonName;
    public string PersonName
    {
        get { return _PersonName; }
        set
        {
            _PersonName = value;
            OnPropertyChanged("PersonName");
        }
    }

    public string Error
    {
        get { return string.Empty; }
    }

    public string this[string columnName]
    {
        get
        {
            if ("PersonName" == columnName)
            {
                if (String.IsNullOrEmpty(PersonName))
                {
                    return "Your Error Message";
                }
            }
        }
    }
}

and also change the xaml as

<TextBox Text="{Binding PersonName, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True, NotifyOnValidationError=True, ValidatesOnExceptions=True, ValidatesOnNotifyDataErrors=True}" />