Exceptions

(407) Proxy Authentication Required.

Saqib Ullah — Sat, 11 Aug 2007 14:30:37 GMT

The remote server returned an error: (407) Proxy Authentication Required.

This is a very common error message when you try to get a resource on internet through your application. Why you getting this error from your application not from explorer. The reason is very simple either you use LAN that requires proxy setting or you use proxy server.

Example :

DataSet myds = new DataSet();
//Set the system proxy with valid server address or IP and port.
System.Net.WebProxy pry = new System.Net.WebProxy("172.16.0.1",8080);
//The DefaultCredentials automically get username and password.
pry.Credentials = CredentialCache.DefaultCredentials;
GlobalProxySelection.Select = pry;
myds.ReadXml("http://msdn.microsoft.com/netframework/rss.xml", XmlReadMode.Auto);
myds.WriteXmlSchema(@"c:\\f.xml");
this.GridView1.DataSource = myds.Tables[2];
this.GridView1.DataBind();

Maximum report processing jobs limit issue in Crystal Report

Saqib Ullah — Wed, 18 Jul 2007 06:42:39 GMT

This is a very common error in Crystal Report when its give this following message.
"The maximum report processing jobs limit configured by your system administrator has been reached."
I have been read about its on lot forums and new groups. Its actually means that Crystal Report print job limit has been reached and you should handle this problem by increasing the job limit in the registry. The basic reason of this problem is Garbag Collector (GC) cannot clear the reference of report document in their collection process its only clear report viewer.
HKEY_LOCAL_MACHINE\SOFTWARE\CRYSTAL DECISIONS\10.0\REPORT APPLICATION SERVER\SERVER\PrintJobLimit
Yesterday we also facing this problem in our application and after lot of discussion in the team we find out a good solution of this problem in the form following factory class because we not facing this problem in whole application.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using CrystalDecisions;
using CrystalDecisions.CrystalReports;
using CrystalDecisions.CrystalReports.Engine;

namespace Test.Utilities
{
    public class ReportFactory
    {
        protected static Queue reportQueue = new Queue();

        protected static ReportClass CreateReport(Type reportClass)
        {
            object report = Activator.CreateInstance(reportClass);
            reportQueue.Enqueue(report);
            return (ReportClass)report;
        }

        public static ReportClass GetReport(Type reportClass)
        {

            //75 is my print job limit.
            if (reportQueue.Count > 75) ((ReportClass)reportQueue.Dequeue()).Dispose();
            return CreateReport(reportClass);
        }
    }
}

You can use this ReportFactory class for creating ReportClass object and don’t need to call explicitly dispose method on the page because ReportFactory class will automatically dispose it when count reach to 75.

BizTalk Rumtime Error "Biztalk Host instance because it is currently running".

Saqib Ullah — Thu, 12 Jul 2007 09:11:23 GMT

When I configuring my BizTalk Server 2006 on WinXP Professional I am facing another problem with the following long text.

Exception:
You cannot request an Install, delete or change credentials operation on this Biztalk Host instance because it is currently running. You must stop the BizTalk host Instance before trying it again.

Fig. 1 BizTalk In-Process Host BizTalkServerApplication Group.

Solution:
One of the simplest solution of this problem is to stop BizTalk Server Application Service from Services Management Console and again apply configuration this time you don't get any exception.

Microsoft.BizTalk.Administration.SnapIn.dll.config Error

Saqib Ullah — Fri, 06 Jul 2007 15:22:59 GMT

Oh my God I am facing another problem in BizTalk Server 2006 when I open BizTalk Server Administrative Tool. I am facing the following error.

Error:
Root element is missing. (D:\Documents and Settings\Administrator\Local Settings\Application Data\Microsoft Corporation\Microsoft BizTalk Server 2006\Microsoft.BizTalk.Administration.SnapIn.dll.config) (System.Configuration)

Reason:
Microsoft.BizTalk.Administration.SnapIn.dll.config is corrupted.

Solution:
Simply delete this file and run BizTalk Server Administrative tool again.

Note:
The next time you start the BizTalk Server 2006 Administration tool, the Administration.Snapin.dll.config file will be auto created for you.

Call assembly from partial trust code

Saqib Ullah — Sat, 14 Apr 2007 04:01:00 GMT

In my last blog we saw the Web application trust levels, how we configure trust level from the application. Strong-named assemblies must be stored in the GAC (short of global assembly cache). By default, strong-named assemblies will not grant access to partially trusted code, because of the visibility of strong-named assemblies in the global assembly cache is high. What going on when partial trusted application call the Full trusted assembly. If the calling assembly marks with the APTCA (short of AllowPartiallyTrustedCallersAttribute) attribute or calling application trust-level set to Full Trust no security exception will throw. Applying the APTCA attribute on the assembly open the luring attacks. It is the responsibilities of the developer to careful evaluates the code and then apply the attribute. Applying the attribute to an assembly without strong-name has no effect.

[assembly: AssemblyKeyFile("..\\..\\keyPair.snk")]
[assembly: AllowPartiallyTrustedCallers]

Note: Apply the above APTCA attribute on the assembly make it callable from the partial trusted caller. Any assembly with AllowPartiallyTrustedCallersAttribute only callable from the fully trusted application.

Internal Working

Very quick questions that come in our mind what is internally going on when APTCA attribute apply to the fully trusted assembly. APTCA in an attribute that simply tell the CLR to remove the implicit LinkDemand. In CAS demand are use to ensure that every caller of the code has been granted (directly or indirectly). Stack walk plays very important role to identify the demanded permission. .Net runtime security walks the call stack, comparing the granted permission of each caller to the permission being demanded. SecurityException throw when the caller found without demanded permission in the stack walk. A Link Demand causes a security check during just-in-time compilation and checks only the immediate caller of the assembly. Permissions are checked only for the immediate caller of code so that why a complete stack walks is not performed.

When this type of demand is performed your will be open for luring attacks. MSDN example “If a method in assembly A is protected by a link demand, a direct caller in assembly B is evaluated based on the permissions of Assembly B. However, the link demand will not evaluate a method in Assembly C if it indirectly calls the method in Assembly A using the method in Assembly B.” The link demand apply only the permission direct callers in the immediate calling assembly must have to link to your code.

When AllowPartiallyTrustedCallerAttribute attribute use on class all security checks function as intended but only block the implicit fully trusted caller demand.

Particle

Here is a simple C# class with AssemblyKeyFile attribute (for strong name) in the AssemblyInfo.cs. Still we do not apply AllowPartiallyTrustedCallers on the assembly.

AssemblyInfo.cs file
[assembly: AssemblyKeyFile("..\\..\\keyPair.snk")]

TestAPTCA.cs file

using System;

using System.Collections.Generic;

using System.Text;

namespace TestAPTCA

{

public class CallFromWeb

{

public string Hello(string name)

{

return "Hello " + name;

}

Compile the class and place it in GAC by using utility from visual studio .Net command prompt gacutil.

e.g. gacutil-i "C:\[Projectpath]\assemblyname.dll

Call Assembly for ASP.Net 2.0 web application

Create simple web application and add reference to the TestAPTCA assembly into the project. I use button and label controls on the page and here is Default.aspx class file code is below.

Defualt.aspx.cs file

using System;

using System.Data;

using System.Configuration;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;

using TestAPTCA; //Should Add namespace of TestAPTCA.dll

public partial class _Default : System.Web.UI.Page

{

protected void Button1_Click(object sender, EventArgs e)

{

CallFromWeb myObj = new CallFromWeb();

Label1.Text = myObj.CallMeFromWeb("Saqib");

}

One last important change in the web.config file, add trust level code in the <system.web> element.

<?xmlversion="1.0"?>

<!--

Note: As an alternative to hand editing this file you can use the

web admin tool to configure settings for your application. Use

the Website->Asp.Net Configuration option in Visual Studio.

A full list of settings and comments can be found in

machine.config.comments usually located in

\Windows\Microsoft.Net\Framework\v2.x\Config

-->

<system.web>

<trustlevel="High" />

<!--

Set compilation debug="true" to insert debugging

symbols into the compiled page. Because this

affects performance, set this value to true only

during development.

-->

<compilationdebug="true">

...

When you run the application and click the button you will get the following exception.

Exception Details: System.Security.SecurityException: That assembly does not allow partially trusted callers.

The solution of this exception is to add AllowPartiallyTrustedCallers attribute that is present in the System.Security namespace into AssemblyInfo.cs file.

using System.Reflection;

using System.Runtime.CompilerServices;

using System.Runtime.InteropServices;

using System.Security;

[assembly: ComVisible(false)]

// The following GUID is for the ID of the typelib if this project is exposed to COM

[assembly: Guid("feebc2d0-6460-40cd-9894-1843f50aa1b9")]

[assembly: AssemblyKeyFile("..\\keyPair.snk")]

[assembly: AllowPartiallyTrustedCallers]

...

Remove trust level code <trustlevel="High"/> from the web.config file and again run the application and this time application run without error.

System.IO.FileLoadException exception

Saqib Ullah — Sat, 07 Apr 2007 04:34:00 GMT

System.IO.FileLoadException exception occur because a managed assembly is found but cannot be loaded. FileLoadException thrown when user and assembly does not have necessary permission for the loading of assembly in the managed environment. When .Net running any assembly its first load into the loader and then loader check the permission against the assembly. Loader checks the assembly permission by the help of evidence. Each assembly loaded by the CLR is also assigned to one or more Machine policy level code groups based on the evidence gathered about the assembly. If in the Machine policy level does not have the permission to write on the C:\ drive and assembly is try load the exception FileloadException is occurred.

Another reason of this exception is when assemblies is marked with the following attributes.
[assembly: FileIOPermission(SecurityAction.RequestMinimum, Write = "C:\\")] its means that whenever this assembly is load by the CLR loader its first check the FileIOPermission for assembly by applying name SecurityAction.RequestMinimum. If Machine policy does not allow the write operation on the C:\ drive and CLR try to load assembly FileLoadException is occurred. RequestMinimum means that CLR first check appropriate permissions option and then load the assembly into the loader.

System.ArithmeticException' occurred in system.drawing.dll

Saqib Ullah — Sun, 19 Nov 2006 02:15:00 GMT

I get this error when i install fresh .net framework 1.1 on my laptop. One surprise problem that i had faced is Exception coming from my System.drawing.dll. Exception is "An unhandled exception of type 'System.ArithmeticException' occurred in system.windows.forms.dll Additional information: Overflow or underflow in the arithmetic operation." After a lot of hard search and reading lot of blogs and forums i didnt find any good solution of this unusual problem. Even MS Help and support the same problem has been reported for CLR 1.0 not for .net 1.1. RESOLUTION Simplly repair yours .net 1.1 framework from control panel.