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Wierd memory leak problem with bitmap class

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This message was discovered on ASPFriends.com 'ngfx-drawing' list.

Michael Lang

I think I've discovered some sort of wierd problem with the bitmap object.
It is illustrated in the code below. The problem seems to be some sort of
memory leak that eventually causes the aspnet_wp.exe to kill itself with the
error:-

aspnet_wp.exe (PID: 2716) was recycled because memory consumption exceeded
the 76 MB (60 percent of available RAM).

Which loses all state data kept on this machine (nasty), this occurs rather
quickly on my test machine as it only has 128 megs of RAM.

The reason why it is wierd is:

1. It does not occur all the time. To repeat the problem I have to rebuild
and start the application at least 3 or 4 times. I find after aspnet_wp has
rebooted it definitely works fine, to get it to fail again you need to go
into Visual Studio and recompile the project.
2. Calls to GC.GetTotalMemory(false); does not return any startling numbers
I have only been able to observe the problem in progress by monitoring the
memory useage and VM Size of the aspnet_wp.exe process in the windows task
manager.
3. In the example below when the bitmap is constructed from the stream there
seems to be a disproportionate increase in aspnet_wp.exe's memory usage.

Can anyone come up with an explanation for this behaviour I'm observing ?
Could someone please tell me if they can repeat this problem or observe the
memory size of aspnet_wp.exe steadily increasing with the following code, if
you could not repeat the problem that would also be useful feedback:-

webform1.aspx:-

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs" AutoEventWireup="false"
Inherits="WebApplication1.WebForm1" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<meta content="Microsoft Visual Studio 7.0" name="GENERATOR">
<meta content="C#" name="CODE_LANGUAGE">
<meta content="JavaScript" name="vs_defaultClientScript">
<meta content="http://schemas.microsoft.com/intellisense/ie5";
name="vs_targetSchema">
</HEAD>
<body MS_POSITIONING="GridLayout">
<form id="Form1" method="post" runat="server">

<asp:Button id="Button1" style="Z-INDEX: 101; LEFT: 247px; POSITION:
absolute; TOP: 88px" runat="server" Height="35px" Width="165px"
Text="Button"></asp:Button>
<asp:Label id="Label1" style="Z-INDEX: 102; LEFT: 253px; POSITION:
absolute; TOP: 51px" runat="server" Width="264px" Height="19px">Click this
button lots</asp:Label>
</form>
</body>
</HTML>

Webform1.aspx.cs:-

using System;
using System.Data;
using System.Drawing;
using System.Web;
using System.IO;

namespace WebApplication1
{
/// <summary>
/// Summary description for WebForm1.
/// </summary>
public class WebForm1 : System.Web.UI.Page
{
protected System.Web.UI.WebControls.Button Button1;
const string filePath = "C:\\... put a path to a image file greater than
100k here... the bigger the better.
protected System.Web.UI.WebControls.Label Label1;
byte[] _myImage = null;
private void Page_Load(object sender, System.EventArgs e)
{
}

#region Web Form Designer generated code
override protected void OnInit(EventArgs e)
{
//
// CODEGEN: This call is required by the ASP.NET Web Form Designer.
//
try
{
_myImage = (byte[])Cache["bitmapData"];
if (_myImage == null)
{
FileStream oFileStream;
oFileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read,
FileShare.Read);
_myImage = new Byte[oFileStream.Length];
oFileStream.Read(_myImage, 0, (int)oFileStream.Length);
oFileStream.Close();

Cache.Add("bitmapData", _myImage, null,
System.Web.Caching.Cache.NoAbsoluteExpiration, TimeSpan.FromMinutes(20),
System.Web.Caching.CacheItemPriority.Normal, null);
}
}
catch
{
}

InitializeComponent();
base.OnInit(e);
}

/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.Button1.Click += new System.EventHandler(this.Button1_Click);
this.Load += new System.EventHandler(this.Page_Load);

}
#endregion

private void Button1_Click(object sender, System.EventArgs e)
{
System.Drawing.Image testBitmap = null;
System.Drawing.Image testBitmap2 = null;
System.Drawing.Image testBitmap3 = null;
System.Drawing.Image testBitmap4 = null;
System.Drawing.Image testBitmap5 = null;
System.Drawing.Image testBitmap6 = null;
System.Drawing.Image testBitmap7 = null;
System.Drawing.Image testBitmap8 = null;
try
{
MemoryStream aStream = new MemoryStream(_myImage);
testBitmap = System.Drawing.Image.FromStream(aStream);
testBitmap2 = System.Drawing.Image.FromStream(aStream);
testBitmap3 = System.Drawing.Image.FromStream(aStream);
testBitmap4 = System.Drawing.Image.FromStream(aStream);
testBitmap5 = System.Drawing.Image.FromStream(aStream);
testBitmap6 = System.Drawing.Image.FromStream(aStream);
testBitmap7 = System.Drawing.Image.FromStream(aStream);
testBitmap8 = System.Drawing.Image.FromStream(aStream);
}
catch
{
if (testBitmap != null) testBitmap.Dispose();
if (testBitmap2 != null) testBitmap2.Dispose();
if (testBitmap3 != null) testBitmap3.Dispose();
if (testBitmap4 != null) testBitmap4.Dispose();
if (testBitmap5 != null) testBitmap5.Dispose();
if (testBitmap6 != null) testBitmap6.Dispose();
if (testBitmap7 != null) testBitmap7.Dispose();
if (testBitmap8 != null) testBitmap8.Dispose();
}

GC.Collect();
}
}
}

Reply to this message...

Joel Mueller

You're only calling Dispose on your Image objects if there's an error.
Try putting that code in a finally block instead of a catch block...

[Original message clipped]

Reply to this message...

	System.Byte
	System.Drawing.Image
	System.EventArgs
	System.EventHandler
	System.GC
	System.IO.FileAccess
	System.IO.FileMode
	System.IO.FileShare
	System.IO.FileStream
	System.IO.MemoryStream
	System.TimeSpan
	System.Web.Caching.Cache
	System.Web.Caching.CacheItemPriority
	System.Web.UI.Page
	System.Web.UI.WebControls.Button
	System.Web.UI.WebControls.Label

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