Use a Thumb to resize a Canvas control by responding to the DragDelta event.

     

<Canvas xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="Thumb_wcp.Pane1">
  <Canvas Width="100" Height="100" Name="myCanvasStretch">
    <TextBox Name="changes" 
         Width="{Binding ElementName=myCanvasStretch,Path=Width}"  
         Height="{Binding ElementName=myCanvasStretch,Path=Height}" 
         Text="Size: 100, 100"/>
    <Thumb Name="myThumb" Canvas.Left="80" Canvas.Top="80" Background="Blue" 
          Width="20" Height="20" DragDelta="onDragDelta"/>
  </Canvas>
</Canvas>
//File:Window.xaml.vb


Imports System
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Controls.Primitives
Imports System.Windows.Documents
Imports System.Windows.Navigation
Imports System.Windows.Shapes
Imports System.Windows.Data
Imports System.Windows.Media

Namespace Thumb_wcp
  Public Partial Class Pane1
    Inherits Canvas
    Private Sub onDragDelta(sender As Object, e As DragDeltaEventArgs)
      Dim yadjust As Double = myCanvasStretch.Height + e.VerticalChange
      Dim xadjust As Double = myCanvasStretch.Width + e.HorizontalChange
      If (xadjust >= 0) AndAlso (yadjust >= 0) Then
        myCanvasStretch.Width = xadjust
        myCanvasStretch.Height = yadjust
        Canvas.SetLeft(myThumb, Canvas.GetLeft(myThumb) + e.HorizontalChange)
        Canvas.SetTop(myThumb, Canvas.GetTop(myThumb) + e.VerticalChange)
        Console.WriteLine(myCanvasStretch.Width)
        Console.WriteLine(myCanvasStretch.Height)
      End If
    End Sub

  End Class
End Namespace

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Use a Thumb to resize a Canvas control by responding to the DragDelta event. : Canvas « Windows Presentation Foundation « VB.Net

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