Slider Inputs

The range, the value, and the bound source

Slider derives from RangeBase, as do ProgressBar and ScrollBar. Minimum, Maximum, Value, SmallChange, and LargeChange come from RangeBase. A new Slider runs from 0 to 10, Value is a double, and its default is 0.

In every case measured, Value was kept inside the range, without exceptions. Setting 150 on a 0–100 Slider gave 100. When Maximum was later raised to 200, Value went back to 150, because the value that was set is remembered. Maximum is kept at or above Minimum: setting Minimum="50" and then Maximum="10" gave an effective Maximum of 50. Because of this, the order in which you change the two does not matter: moving the range from 0–10 to 100–200 ended in the same state whichever was set first.

The correction is not written back to a source: a source value of 150, bound two-way to a 0–100 Slider, stayed 150 while the Slider showed 100. Keep the source inside the range yourself, or it holds a value the Slider does not show.

Value binds two-way by default, and its default UpdateSourceTrigger is PropertyChanged, so no UpdateSourceTrigger is needed. With default binding settings, the source received the value in the middle of a drag, before the mouse button was released. If the source’s setter does heavy work, that work runs on every drag step.

Keys, clicks on the track, and direction

SmallChange is the step for the arrow keys, and LargeChange the step for Page Up / Page Down and for clicks on the track. The defaults are 0.1 and 1, which suit the default 0–10 range, not a 0–100 one such as a volume. With 1 and 10 on a Slider at 50, the right and up arrows gave 51, the left arrow 49, Page Up 60, Page Down 40, and a real mouse click on the track right of the thumb 60. That is with IsMoveToPointEnabled at its default, False. With True, the same click moved the thumb to the point clicked instead, and the value became 86.84. Home and End jumped to Minimum and Maximum.

Holding the mouse button down on the track repeats the step. Delay is the wait before repeating and Interval the time between repeats. Their defaults come from the Windows keyboard settings: on the measuring machine, where SystemParameters.KeyboardDelay was 1 and KeyboardSpeed 31, they were 500 and 33, and the Delay default matched (KeyboardDelay + 1) × 250. The Slider passes them to the two RepeatButtons of its track: with the demo app’s 1000 and 50, both buttons had Delay="1000" and Interval="50". A click released before Delay ran out moved the value once, by LargeChange.

Orientation defaults to Horizontal. At Value = Maximum, the thumb was at the right end of a horizontal Slider and at the top of a vertical one, so a vertical Slider already puts large values at the top. IsDirectionReversed reverses the track: at Value = Maximum, the thumb moved to the left end of a horizontal Slider and to the bottom of a vertical one. The keys follow the track: the right arrow decreased the value (50 to 49).

Snapping applies only to what the user does

Drawing tick marks does not snap to them: with only TickPlacement="BottomRight", a drag to 23.4 left the value at 23.4. IsSnapToTickEnabled, whose default is False, makes user input snap to the nearest tick. A drag to 23.4 gave 20 with TickFrequency="10" and 23 with TickFrequency="1". The value snaps while the thumb is being dragged, not only when it is released. It also changes the keys and the track: with TickFrequency="10", the right arrow moved 50 to 60 instead of 51, and a click on the track with LargeChange="7" moved 50 to 60 instead of 57. A value of 23.4 set from code stayed 23.4.

TickFrequency, whose default is 1, sets the spacing of the snap positions. Maximum was also a snap position: with TickFrequency="30" on 0–100, a drag to 94 snapped to 90, and a drag to 97 snapped to 100. Ticks lists the positions explicitly and replaces TickFrequency; for discrete sizes or levels, list them there with snapping on. With 1,3,5,7,9 on a 0–10 Slider, a drag to 5.8 gave 5, and a drag to 0.2 gave 0: Minimum and Maximum are snap positions even when they are not in Ticks.

Value after dragging the thumb, with and without snapping. Only the last row is the value of the source bound to Value, read during the drag. Measured on .NET 10 / Windows 11.

Tick marks, the selection range, and the tooltip

In the cases measured, tick marks were drawn at Minimum and Maximum even when the frequency did not divide the range: with TickFrequency="30" on 0–100, marks were drawn at 0, 30, 60, 90, and 100, and Ticks="1,3,5,7,9" on 0–10 drew marks at 0, 1, 3, 5, 7, 9, and 10. IsDirectionReversed reverses the tick marks as well: with Ticks="1,2" on 0–10, the marks moved to the right end of the track. Only labels you draw yourself next to the Slider have to be reordered by hand. TickPlacement defaults to None, and tick marks take space: a horizontal Slider was 18 high with None, 24 with BottomRight, and 30 with Both.

SelectionStart and SelectionEnd highlight a part of the track. With 2 to 8 on 0–10, the highlight was hidden while IsSelectionRangeEnabled was False, its default. With True, it covered the track from 2 to 8. The selection does not limit Value: a value of 9.5 could still be set.

AutoToolTipPlacement shows a tooltip with the current value while the thumb is dragged; the default None shows none. The text is a plain number. Slider has no property for its format, as the only related properties are AutoToolTipPlacement and AutoToolTipPrecision. The number follows the current culture: 1234.56 with one decimal was shown as 1,234.6 with en-US and as 1.234,6 with de-DE. AutoToolTipPrecision, whose default is 0, rounds rather than truncates: with 0, a value of 33.6 was shown as 34 and 33.4 as 33. With 2, 33.456 was shown as 33.46. Only the tooltip is rounded; Value keeps its full precision. For units such as “%”, show the value in a separate TextBlock with a StringFormat.

Tick marks (as values, left to right), heights, the selection range, and the automatic tooltip text. Measured on .NET 10 / Windows 11.

Trying it in the demo app

The Slider page of the demo app has a section for each property above. The SmallChange / LargeChange section starts with 1 and 10 on a 0–10 Slider, so one Page Up or one click on the track already moves the thumb across the whole range; the Ticks section uses 1,3,5,7,9; the selection section uses 2 to 8; and the Delay / Interval section uses 1000 and 50. The “Show Code” link under each section displays its XAML. The following XAML is the Minimum / Maximum / Value section (SliderUsageControl.xaml), with the styles and the surrounding GroupBoxes left out and the namespace declarations added. behaviors is the prefix for the demo app’s own attached behaviors:

<StackPanel xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:behaviors="clr-namespace:WPFStandardControlDemoApp.Common.Behaviors">
  <TextBox x:Name="MinTextBox"
           behaviors:TextBoxDoubleInputBehavior.IsEnabled="True"
           Text="0" />
  <TextBox x:Name="MaxTextBox"
           behaviors:TextBoxDoubleInputBehavior.IsEnabled="True"
           Text="100" />
  <TextBox x:Name="ValueTextBox"
           behaviors:TextBoxDoubleInputBehavior.IsEnabled="True"
           Text="{Binding Value, ElementName=MinMaxSlider, UpdateSourceTrigger=PropertyChanged}" />

  <Slider x:Name="MinMaxSlider"
          Maximum="{Binding Text, ElementName=MaxTextBox}"
          Minimum="{Binding Text, ElementName=MinTextBox}" />
</StackPanel>

The UpdateSourceTrigger=PropertyChanged here belongs to the binding on TextBox.Text, whose default is LostFocus. It makes typing in the text box move the Slider at once. A binding on Slider.Value needs no such setting, because its default is already PropertyChanged.

Related controls and articles

• ProgressBar — also derives from RangeBase; it displays a value in a range.
• RepeatButton — the button type that the Slider’s track uses for clicks and repeats.

Source code and how it was measured

Every behavior on this page was measured by running it on .NET 10 / Windows 11, using SliderDemoScene in this site’s screenshot tool. Thumb drags were reproduced by raising the same DragStarted and DragDelta events that the thumb raises for a mouse drag, and keys by sending key events to a displayed window. Clicks on the track were made with the real mouse over the measuring window, at 85% of the track’s length, with the button released after about 0.1 s.

View Slider source code on GitHub →