Set focus on PasswordBox Problem

I want to show  password box with typing cursor for that we can start direct typing without setting cursor.

<PasswordBox  Name="passwordTextbox" Grid.Row="1" Grid.Column="1" Margin="5,35,5,5" Width="280"

Height="27" app:PasswordBoxAssistant.BindPassword="true"

app:PasswordBoxAssistant.BoundPassword="{Binding TechUserModel.UserId, Mode=TwoWay, ValidatesOnDataErrors=True,

UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left"></PasswordBox>

I am setting focus by programming

passwordTextbox.Focus();

It's showing cursor but not start typing without setting cursor again. Can I show PasswordBox with default running cursor ? please provide any one solution.