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AutoDisposeImages Property

Summary

Gets or sets a value indicating whether to automatically dispose item images.

Syntax

C++

public bool AutoDisposeImages { get; set; }

Public Property AutoDisposeImages As Boolean

public: 
property bool AutoDisposeImages { 
   bool get(); 
   void set (    bool ); 
}

Property Value

true to automatically dispose item images; false, otherwise. Default value is true.

Remarks

When the value of the AutoDisposeImages is set to true, the RasterImageList control will automatically call the RasterImage.Dispose method on an item's RasterImageListItem.Image when the item is removed from the Items collection or when the control itself is disposed.

The control will check if an image is used with multiple items (for example, if multiple items are using the same image but to show different pages). In this case, the control will correctly dispose the image only once.

If you setup the items with images that you do not want to dispose of and are going to re-use somewhere else, you need to set the value of the AutoDisposeImages property of the RasterImageList control to false.

You can also temporarily change the value of the AutoDisposeImages property if you want to save the item image before you dispose it. For example, set the AutoDisposeImages property to false, call Remove on the Items collection to remove the item, then re-set the AutoDisposeImages property back to true.

Note that if you set the AutoDisposeImages value to false and you do not dispose the item images yourself, the .NET garbage collector will eventually detect that these images are not used anymore and will dispose them for you when the control and any other reference to these images are no longer used in your application.

Example

This example removes an item from the control and demonstrates how the AutoDisposeImages property effects whether the item image remains usable.

using Leadtools.WinForms; 
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.Drawing; 
 
public void RasterImageList_AutoDisposeImages(RasterImageList imageList) 
{ 
   // Make sure the AutoDisposeImages property is set to true 
   imageList.AutoDisposeImages = true; 
 
   MessageBox.Show("Removing an item then accessing its image with AutoDisposeImages set to true"); 
 
   // Remove the first item 
   RasterImageListItem item = imageList.Items[0]; 
   imageList.Items.RemoveAt(0); 
 
   // Try to save this item's image into a disk file 
   // This will throw an exception since the item image has been dispose 
   // as a result of having the AutoDisposeImages false set to true 
   RasterCodecs codecs = new RasterCodecs(); 
   try 
   { 
      codecs.Save(item.Image, Path.Combine(LEAD_VARS.ImagesDir, "Test.jpg"), RasterImageFormat.Jpeg, 24); 
      MessageBox.Show("Image saved correctly"); 
   } 
   catch (Exception ex) 
   { 
      MessageBox.Show(ex.Message); 
   } 
 
   MessageBox.Show("Removing an item then accessing its image with AutoDisposeImages set to false"); 
 
   // Now remove the next item, this time make sure to set the 
   // AutoDisposeImages property to false before you remove the item 
   // from the control collection 
   item = imageList.Items[0]; 
 
   imageList.AutoDisposeImages = false; 
   imageList.Items.RemoveAt(0); 
   imageList.AutoDisposeImages = true; 
 
   // Try to save this item's image into a disk file 
   // This time, this should work correcly since the control did not dispose 
   // the item image. 
   try 
   { 
      codecs.Save(item.Image, Path.Combine(LEAD_VARS.ImagesDir, "Test.jpg"), RasterImageFormat.Jpeg, 24); 
      MessageBox.Show("Image saved correctly"); 
   } 
   catch (Exception ex) 
   { 
      MessageBox.Show(ex.Message); 
   } 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images"; 
}

Imports Leadtools.WinForms 
Imports Leadtools 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
 
Public Sub RasterImageList_AutoDisposeImages(ByVal imageList As RasterImageList) 
   ' Make sure the AutoDisposeImages property is set to true 
   imageList.AutoDisposeImages = True 
 
   MessageBox.Show("Removing an item then accessing its image with AutoDisposeImages set to true") 
 
   ' Remove the first item 
   Dim item As RasterImageListItem = imageList.Items(0) 
   imageList.Items.RemoveAt(0) 
 
   ' Try to save this item's image into a disk file 
   ' This will throw an exception since the item image has been disposed of 
   ' as a result of having the AutoDisposeImages false set to true 
   Dim codecs As RasterCodecs = New RasterCodecs() 
   Try 
      codecs.Save(item.Image, Path.Combine(LEAD_VARS.ImagesDir, "Test.jpg"), RasterImageFormat.Jpeg, 24) 
      MessageBox.Show("Image saved correctly") 
   Catch ex As Exception 
      MessageBox.Show(ex.Message) 
   End Try 
 
   MessageBox.Show("Removing an item then accessing its image with AutoDisposeImages set to false") 
 
   ' Now remove the next item, this time make sure to set the 
   ' AutoDisposeImages property to false before you remove the item 
   ' from the control collection 
   item = imageList.Items(0) 
 
   imageList.AutoDisposeImages = False 
   imageList.Items.RemoveAt(0) 
   imageList.AutoDisposeImages = True 
 
   ' Try to save this item's image into a disk file 
   ' This time, this should work correcly since the control did not dispose 
   ' the item image. 
   Try 
      codecs.Save(item.Image, Path.Combine(LEAD_VARS.ImagesDir, "Test.jpg"), RasterImageFormat.Jpeg, 24) 
      MessageBox.Show("Image saved correctly") 
   Catch ex As Exception 
      MessageBox.Show(ex.Message) 
   End Try 
End Sub 
 
Public NotInheritable Class LEAD_VARS 
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images" 
End Class

Requirements

Target Platforms

Reference

RasterImageList Class

RasterImageList Members

Help Version 19.0.2017.10.27

Leadtools.WinForms Assembly

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Leadtools.WinForms Namespace

Assemblies