WPF

public partial class WizPgQuery : WizardPageBase, IDataErrorInfo
{
    public string this[string columnName]
    {
        get
        {
            string value;
            switch (columnName)
            {
                case "ClassName": value = this.ValidateClassName(); break;
                case "QueryText": value = this.ValidateQueryText(); break;
                default         : value = string.Empty;             break;
            }
            return value;
        }
    }

    public string Error
    {
        get { throw new NotImplementedException(); }
    }

private string className;
public string ClassName
{
    get { return this.className; }
    set
    {
        if (value != this.className)
        {
            this.className = value;
            this.NotifyPropertyChanged();
        }
    }
}

private string ValidateClassName()
{
    string value = (this.ClassName.IsValidClassName())
                    ? ""
                    : "The class name must be a valid C# identifier.";
    // just to make sure it's getting called
    if (!string.IsNullOrEmpty(value)) { SystemSounds.Beep.Play(); }
    return value;
}

<TextBox x:Name="textboxClassName" Grid.Column="1" 
         Text="{Binding Path=ClassName, 
         Mode=TwoWay, 
         ValidatesOnDataErrors=True, 
         ValidatesOnExceptions=True, 
         NotifyOnValidationError=True,
         UdateSourceTrigger=PropertyChanged}"
         TextChanged="TextboxClassName_TextChanged" 
         ToolTip="Base tool tip" />

public static readonly DependencyProperty ProjectProperty =
            DependencyProperty.Register("Project",
            typeof(ProjectEntity),
            typeof(PurchaseOrderView),
            new PropertyMetadata(null, new PropertyChangedCallback(OnProjectChanged)));

public ProjectEntity Project
{
    get { return (ProjectEntity)GetValue(ProjectProperty); }
    set { SetValue(ProjectProperty, value); }
}

private static void OnProjectChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    PurchaseOrderView control = (PurchaseOrderView)d;
    control.LoadPurchaseOrders();
}
<h1>endregion</h1>

<Style.Triggers>
    <MultiDataTrigger>
        <MultiDataTrigger.Conditions>
            <Condition Binding="{Binding AreFieldsEnabled}" Value="True" />
            <Condition Binding="{Binding CanUserEdit}" Value="True" />
        </MultiDataTrigger.Conditions>
        <MultiDataTrigger.Setters>
            <Setter Property="IsEnabled" Value="True" />
        </MultiDataTrigger.Setters>
    </MultiDataTrigger>
</Style.Triggers>

Private Sub bwstartup_DoWork(sender As Object, e As DoWorkEventArgs) Handles bwstartup.DoWork
        'load some data
        LoadData()
        bwstartup.ReportProgress(15)
        LoadData2()  
        bwstartup.ReportProgress(20)

        Dispatcher.Invoke(Sub() LoadUserControl())
        bwstartup.ReportProgress(30)
       
        Dispatcher.Invoke(Sub() LoadUserControl2())
        bwstartup.ReportProgress(40)
    End Sub

    Private Sub bwstartup_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles bwstartup.ProgressChanged
        loadingbar.Value = e.ProgressPercentage
    End Sub

    Private Sub bwstartup_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles bwstartup.RunWorkerCompleted

    End Sub