AutoDisposeImages Property (RasterImageViewer)

Gets or sets a value indicating whether to auto dispose the old image when a new image is set into this RasterImageViewer.

Syntax

Visual Basic
C#
WinRT C#
WinRT JavaScript
C++

[DescriptionAttribute("Indicating whether to auto dispose the old image when a new image is set into this control")]
[CategoryAttribute("Behavior")]
public virtual bool AutoDisposeImages {get; set;}

'Declaration
 
<DescriptionAttribute("Indicating whether to auto dispose the old image when a new image is set into this control")>
<CategoryAttribute("Behavior")>
Public Overridable Property AutoDisposeImages As Boolean

'Usage
 
Dim instance As RasterImageViewer
Dim value As Boolean
 
instance.AutoDisposeImages = value
 
value = instance.AutoDisposeImages

[DescriptionAttribute("Indicating whether to auto dispose the old image when a new image is set into this control")]
[CategoryAttribute("Behavior")]
public virtual bool AutoDisposeImages {get; set;}

DescriptionAttribute("Indicating whether to auto dispose the old image when a new image is set into this control")
CategoryAttribute("Behavior")
 get_AutoDisposeImages();
 set_AutoDisposeImages(value);

[DescriptionAttribute("Indicating whether to auto dispose the old image when a new image is set into this control")]
[CategoryAttribute("Behavior")]
public:
virtual property bool AutoDisposeImages {
   bool get();
   void set (    bool value);
}

Property Value

true if the image in Image is automatically disposed when a new image is set; otherwise, false. Default value is true.

Remarks

By default, whenever you set a new image into the Image property, the old image (if any) is disposed. Set the value of this property to false to prevent disposing of the old image.

Example

Visual Basic
C#
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Private Sub viewer_ImageChanged(ByVal sender As Object, ByVal e As EventArgs)
      Dim viewer As RasterImageViewer = CType(IIf(TypeOf sender Is RasterImageViewer, sender, Nothing), RasterImageViewer)
      Dim s As String
      If Not viewer.Image Is Nothing Then
         s = String.Format("Image Changed: New Width {0}, NewHeight {1}", viewer.Image.Width, viewer.Image.Height)
      Else
         s = "No Image"
      End If
      Console.WriteLine(s)
   End Sub

   Public Sub RasterImageViewer_AutoDisposeImages(ByVal viewer As RasterImageViewer)
      ' Load two image2
      Dim codecs As RasterCodecs = New RasterCodecs()
      Dim file1 As String = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp")
      Dim file2 As String = Path.Combine(LEAD_VARS.ImagesDir, "Image2.cmp")

      AddHandler viewer.ImageChanged, AddressOf viewer_ImageChanged

      Dim image1 As RasterImage = codecs.Load(file1)
      Dim image2 As RasterImage = codecs.Load(file2)

      ' Make sure the AutoDisposeImages property of the viewer is set to true
      viewer.AutoDisposeImages = True

      ' Set the first image into the viewer
      viewer.Image = image1

      ' Now set the second image into the viewer (this disposes the first image since the AutoDisposeImages property is true)
      viewer.Image = image2

      ' Try to access the first image, it generates a NullReferenceException exception since the image has been disposed
      MessageBox.Show("Try to access the first image, it generates a NullReferenceException exception since the image has been disposed.")
      Try
         Dim width As Integer = image1.Width
         MessageBox.Show(String.Format("Width is {0} pixels", width))
      Catch ex As NullReferenceException
         MessageBox.Show(ex.Message)
      End Try

      ' Set the image to null (will dispose the second image as well)
      viewer.Image = Nothing

      ' Now re-load the two images
      image1 = codecs.Load(file1)
      image2 = codecs.Load(file2)

      ' Make sure the AutoDisposeImages property of the viewer is set to false
      viewer.AutoDisposeImages = False

      ' Set the first image into the viewer
      viewer.Image = image1

      ' Now set the second image into the viewer (this will not disposes the first image since the AutoDisposeImages property is false)
      viewer.Image = image2

      ' Try to access the first image, it should work fine this time
      Try
         Dim width As Integer = image1.Width
         MessageBox.Show(String.Format("Width is {0} pixels", width))
      Catch ex As NullReferenceException
         MessageBox.Show(ex.Message)
      End Try

      ' Set the image to null (will not dispose the second image)
      viewer.Image = Nothing

      ' We should now dispose the two images manually
      image1.Dispose()
      image2.Dispose()

      RemoveHandler viewer.ImageChanged, AddressOf viewer_ImageChanged
   End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

private void viewer_ImageChanged(object sender, EventArgs e)
   {
      RasterImageViewer viewer = sender as RasterImageViewer;
      string s;
      if (viewer.Image != null)
         s = string.Format("Image Changed: New Width {0}, NewHeight {1}", viewer.Image.Width, viewer.Image.Height);
      else s = "No Image";
      Console.WriteLine(s);
   }

   public void RasterImageViewer_AutoDisposeImages(RasterImageViewer viewer)
   {
      // Load two image2
      RasterCodecs codecs = new RasterCodecs();
      string file1 = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp");
      string file2 = Path.Combine(LEAD_VARS.ImagesDir, "Image2.cmp");

      viewer.ImageChanged += new EventHandler(viewer_ImageChanged);

      RasterImage image1 = codecs.Load(file1);
      RasterImage image2 = codecs.Load(file2);

      // Make sure the AutoDisposeImages property of the viewer is set to true
      viewer.AutoDisposeImages = true;

      // Set the first image into the viewer
      viewer.Image = image1;

      // Now set the second image into the viewer (this disposes the first image since the AutoDisposeImages property is true)
      viewer.Image = image2;

      // Try to access the first image, it generates a NullReferenceException exception since the image has been disposed
      MessageBox.Show("Try to access the first image, it generates a NullReferenceException exception since the image has been disposed.");
      try
      {
         int width = image1.Width;
         MessageBox.Show(string.Format("Width is {0} pixels", width));
      }
      catch (NullReferenceException ex)
      {
         MessageBox.Show(ex.Message);
      }

      // Set the image to null (will dispose the second image as well)
      viewer.Image = null;

      // Now re-load the two images
      image1 = codecs.Load(file1);
      image2 = codecs.Load(file2);

      // Make sure the AutoDisposeImages property of the viewer is set to false
      viewer.AutoDisposeImages = false;

      // Set the first image into the viewer
      viewer.Image = image1;

      // Now set the second image into the viewer (this will not disposes the first image since the AutoDisposeImages property is false)
      viewer.Image = image2;

      // Try to access the first image, it should work fine this time
      try
      {
         int width = image1.Width;
         MessageBox.Show(string.Format("Width is {0} pixels", width));
      }
      catch (NullReferenceException ex)
      {
         MessageBox.Show(ex.Message);
      }

      // Set the image to null (will not dispose the second image)
      viewer.Image = null;

      // We should now dispose the two images manually
      image1.Dispose();
      image2.Dispose();

      viewer.ImageChanged -= new EventHandler(viewer_ImageChanged);
   }

static class LEAD_VARS
{
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

RasterImageViewer Class
RasterImageViewer Members