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title, ms.date, dev_langs, helpviewer_keywords, ms.assetid
| title | ms.date | dev_langs | helpviewer_keywords | ms.assetid | |||
|---|---|---|---|---|---|---|---|
| How to: Get or Set Canvas Positioning Properties | 03/30/2017 |
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1636b950-2b5a-4507-8a10-c5034cc58b1c |
How to: Get or Set Canvas Positioning Properties
This example shows how to use the positioning methods of the xref:System.Windows.Controls.Canvas element to position child content. This example uses content in a xref:System.Windows.Controls.ListBoxItem to represent positioning values and converts the values into instances of xref:System.Double, which is a required argument for positioning. The values are then converted back into strings and displayed as text in a xref:System.Windows.Controls.TextBlock element by using the xref:System.Windows.Controls.Canvas.GetLeft%2A method.
Example
The following example creates a xref:System.Windows.Controls.ListBox element that has eleven selectable xref:System.Windows.Controls.ListBoxItem elements. The xref:System.Windows.Controls.Primitives.Selector.SelectionChanged event triggers the ChangeLeft custom method, which the subsequent code block defines.
Each xref:System.Windows.Controls.ListBoxItem represents a xref:System.Double value, which is one of the arguments that the xref:System.Windows.Controls.Canvas.SetLeft%2A method of xref:System.Windows.Controls.Canvas accepts. In order to use a xref:System.Windows.Controls.ListBoxItem to represent an instance of xref:System.Double, you must first convert the xref:System.Windows.Controls.ListBoxItem to the correct data type.
[!code-xamlCanvasPositioningProperties#1]
When a user changes the xref:System.Windows.Controls.ListBox selection, it invokes the ChangeLeft custom method. This method passes the xref:System.Windows.Controls.ListBoxItem to a xref:System.Windows.LengthConverter object, which converts the xref:System.Windows.Controls.ContentControl.Content%2A of a xref:System.Windows.Controls.ListBoxItem to an instance of xref:System.Double (notice that this value has already been converted to a xref:System.String by using the xref:System.Windows.Controls.Control.ToString%2A method). This value is then passed back to the xref:System.Windows.Controls.Canvas.SetLeft%2A and xref:System.Windows.Controls.Canvas.GetLeft%2A methods of xref:System.Windows.Controls.Canvas in order to change the position of the text1 object.
[!code-csharpCanvasPositioningProperties#2] [!code-vbCanvasPositioningProperties#2]