PasswordBox Inputs

Why Password cannot be bound, and how to get the value out

PasswordBox derives from Control, not from TextBoxBase. Its Password property is a plain CLR property: there is no PasswordProperty, so it cannot be the target of a binding. The value can still be set from code or in XAML. The demo app sets Password="PASSWORD" as an attribute, and that value was read back unchanged.

To pass the value to a ViewModel, use PasswordChanged or an attached behavior. PasswordChanged was raised once per typed character (three times for “abc”), once for setting Password from code, and once for Clear(), so a handler sees every change. Clear() emptied Password; call it when the value is no longer needed.

Internally, the text is held in a SecureString field of a PasswordTextContainer. Password returns it as an ordinary string. SecurePassword returned a new, writable SecureString on every call, not the same instance. Code that uses it owns that copy, and should dispose of it.

PasswordChar, unlike Password, is a dependency property. Its metadata default is *, but the default style sets ● (U+25CF), so that is what you see.

Type, properties, defaults, and how the password is held. Measured on .NET 10 / Windows 11.

What MaxLength, Copy, and IsSelectionActive actually do

MaxLength limits only typing; the default is 0 (unlimited). With MaxLength="8", typing “1234567890” left “12345678”. Password set from code was not cut: it kept all ten characters. Treat MaxLength as an input aid, and check the length where the value is used.

With all text selected, the Copy and Cut commands could not be executed, while Paste could.

IsSelectionActive is read-only and, despite its name, does not report whether text is selected. It was True as soon as the PasswordBox had focus with nothing selected, still True with all text selected, and False after focus moved to another control even though the selection was kept. It follows keyboard focus, so do not use it to detect a selection.

Input, events, clipboard commands, and IsSelectionActive. Measured on .NET 10 / Windows 11.

The caret and the selection highlight

CaretBrush defaults to null. SelectionBrush gets its default from the property’s default value, not from a style; on the measuring machine it was #FF0078D7. SelectionOpacity defaults to 0.4. IsInactiveSelectionHighlightEnabled decides whether the selection stays highlighted after the PasswordBox loses focus; its default is False. The highlight itself is drawn on screen and was not measured on this page.

Trying it in the demo app

The PasswordBox page of the demo app has a section for each of CaretBrush, IsInactiveSelectionHighlightEnabled, IsSelectionActive, MaxLength, PasswordChar, SelectionBrush, and SelectionOpacity. The brushes are picked from a list of named brushes, over a PasswordBox that starts with “PASSWORD”; MaxLength starts with 8 and SelectionOpacity with 0.5, typed into text boxes; the IsInactiveSelectionHighlightEnabled section starts with True and places two PasswordBoxes so that focus can be moved between them. The “Show Code” link under each section displays its XAML. The following XAML is the PasswordChar section (PasswordBoxUsageControl.xaml), with the styles and the surrounding GroupBoxes left out and the namespace declarations added. The binding takes the first character of the text box and falls back to ● when it is empty:

<StackPanel xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <TextBox x:Name="PasswordCharTextBox" MaxLength="1" Text="*" />

  <PasswordBox x:Name="PasswordCharPasswordBox"
               PasswordChar="{Binding Text[0], ElementName=PasswordCharTextBox, FallbackValue=●}" />
</StackPanel>

Related controls and articles

• TextBox — plain text input; MaxLength behaves the same way there.
• Label — text that names the field next to it.

Source code and how it was measured

Every behavior on this page was measured by running it on .NET 10 / Windows 11, using PasswordBoxDemoScene in this site’s screenshot tool. Typing was reproduced one character at a time with TextCompositionManager, which delivers text through the same TextInput path as the keyboard. The clipboard was not touched: only whether the Copy, Cut, and Paste commands could execute was read.

View PasswordBox source code on GitHub →