Check PasswordBox if user type anything in WPF

Question

I am using PasswordBox and I want to detect whenever the user typed there anything, if yes I need to change Button status to enabled. How can I check if user types anything in the PasswordBox?

It behaves differently from TextBox since you can't bind it to text and when user types anything raises some event. Any idea?

I have tried with the code below, but I get errors:

<PasswordBox>
    <i:Interaction.Triggers>
        <EventTrigger EventName="KeyDown">
            <si:InvokeDataCommand Command="{Binding MyCommand}" />
        </EventTrigger>
    </i:Interaction.Triggers>  
</PasswordBox>

Answer 1

You can use the PasswordChanged event via Interactions like this:

XAML

xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"

<PasswordBox BorderBrush="#FFB0B1AB"
             Width="100"
             Height="25"
             VerticalAlignment="Bottom">

    <i:Interaction.Triggers>
        <i:EventTrigger EventName="PasswordChanged">
            <i:InvokeCommandAction Command="{Binding PasswordChangedCommand}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
</PasswordBox>

RelayCommand

private ICommand _passwordChangedCommand = null;

public ICommand PasswordChangedCommand
{
    get
    {
        if (_passwordChangedCommand == null)
        {
            _passwordChangedCommand = new RelayCommand(param => this.PasswordChanged(), null);
        }

        return _passwordChangedCommand;
    }
}

private void PasswordChanged()
{
    // your logic here
}

Some useful links

PasswordBox in WPF Tutorial

Binding to PasswordBox in WPF (using MVVM)

How to bind to a PasswordBox in MVVM