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 (Declaration) | |
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<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 |
Visual Basic (Usage) | Copy Code |
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Dim instance As RasterImageViewer
Dim value As Boolean
instance.AutoDisposeImages = value
value = instance.AutoDisposeImages
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Managed Extensions for C++ | |
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[DescriptionAttribute("Indicating whether to auto dispose the old image when a new image is set into this control")]
[CategoryAttribute("Behavior")]
public: __property virtual bool get_AutoDisposeImages();
public: __property virtual void set_AutoDisposeImages(
bool value
); |
Return Value
true if the image in
Image is automatically disposed when a new image is set; otherwise, false. Default value is true.
Example
This sample loads two images to demonstrate how the AutoDisposeImages property effects
whether the item image remains usable.
Visual Basic | Copy Code |
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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)
RasterCodecs.Startup()
Dim codecs As RasterCodecs = New RasterCodecs()
Dim file1 As String = "C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\Image1.cmp"
Dim file2 As String = "C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\Image2.cmp"
AddHandler viewer.ImageChanged, AddressOf viewer_ImageChanged
Dim image1 As RasterImage = codecs.Load(file1)
Dim image2 As RasterImage = codecs.Load(file2)
viewer.AutoDisposeImages = True
viewer.Image = image1
viewer.Image = image2
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
viewer.Image = Nothing
image1 = codecs.Load(file1)
image2 = codecs.Load(file2)
viewer.AutoDisposeImages = False
viewer.Image = image1
viewer.Image = image2
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
viewer.Image = Nothing
image1.Dispose()
image2.Dispose()
RemoveHandler viewer.ImageChanged, AddressOf viewer_ImageChanged
End Sub |
C# | Copy Code |
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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.Startup(); RasterCodecs codecs = new RasterCodecs(); string file1 = @"C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\Image1.cmp"; string file2 = @"C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\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); } |
Remarks
Requirements
Target Platforms: Microsoft .NET Framework 2.0, Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family
See Also