how to set focus on a textbox or passwordbox - wpf

Question

how to set focus on this when i log in to my application ,when log in window will open i want to type the password on this without using mouse
<PasswordBox x:Name="passwordbox" 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" VerticalAlignment="Center">

Answer 1

I have tried various solutions for this scenario and the most effective that I have found is using FocusManager.FocusedElement:
<Window x:Class="StackOverflow.Test"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Test" Height="300" Width="300"
FocusManager.FocusedElement="{Binding ElementName=Box}">
<Grid>
<TextBox x:Name="Box"/>
</Grid>
</Window>

Answer 2

SOLUTION:
passwordbox.Focus();
or in .xaml file include the following in the element as its attributes.
FocusManager.FocusedElement="{Binding ElementName=passwordbox}">
NOTE:
If you want to decide which control to give focus to when the form first appears, put the code in the Loaded event.
Loaded += (o, e) => {
passwordbox.Focus();
};