getting System.Reflection.TargetInvocationException while trying to change the AD password of an user from web apps using C#

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C#

ASP.NET

Hi,

I'm having this problem and I'm not able to solve this for a while now. The scenario is like any user of my web apps can change their application password and the corresponding Server AD ID password from the application itself. I'm using .NET 3.5 framework and was came to know that by using the namespace called
System.DirectoryServices.AccountManagement we can do any AD ID manupulation by writing C# code. I've used the below code to change the AD password of the user.

#region SetUserDomainPassword for setting the new password as domain password
private bool SetUserDomainPassword(string strUserId, string strNewPassword)
{
bool blnflag = false;
try
{
UserPrincipal oUserPrincipal = GetUser(strUserId);
oUserPrincipal.SetPassword(strNewPassword);blnflag = true;
return blnflag;
}
 
catch (Exception ex)
{ 
ExceptionPolicy.HandleException(ex, "EPolicy");
return blnflag;
}
}
#endregion
#region GetUser for getting the user info
public UserPrincipal GetUser(string sUserName)
{
PrincipalContext oPrincipalContext = GetPrincipalContext();
UserPrincipal oUserPrincipal =
UserPrincipal.FindByIdentity(oPrincipalContext, sUserName);
return oUserPrincipal;
}
#endregion
#region GetPrincipalContext for getting the principalCOntext
public PrincipalContext GetPrincipalContext()
{
PrincipalContext oPrincipalContext = new PrincipalContext(ContextType.Domain);
return oPrincipalContext;
}
#endregion 

Here, I'm calling the "SetUserDomainPassword" method with the AD user ID and the new password sent as the parameters. The problem I'm facing is when ever it is executing the underlined code above it is throwing an exception which is exactly like below.

Timestamp: 11/2/2010 7:45:29 AM
Message: HandlingInstanceID: 7eb8e4c2-51e4-4488-b8dc-84e9a9aba48c
An exception of type 'System.Reflection.TargetInvocationException' occurred and was caught.

-------------------------------------------------------------------------------------------
11/02/2010 03:45:29
Type : System.Reflection.TargetInvocationException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Message : Exception has been thrown by the target of an invocation.
Source : System.DirectoryServices
Help link : 
Data : System.Collections.ListDictionaryInternal
TargetSite : System.Object Invoke(System.String, System.Object[])
Stack Trace :    at System.DirectoryServices.DirectoryEntry.Invoke(String methodName, Object[] args)
   at System.DirectoryServices.AccountManagement.SDSUtils.SetPassword(DirectoryEntry de, String newPassword)
   at System.DirectoryServices.AccountManagement.ADStoreCtx.SetPassword(AuthenticablePrincipal p, String newPassword)
   at System.DirectoryServices.AccountManagement.PasswordInfo.SetPassword(String newPassword)
   at System.DirectoryServices.AccountManagement.AuthenticablePrincipal.SetPassword(String newPassword)
   at login.SetUserDomainPassword(String strUserId, String strNewPassword)
Additional Info:
MachineName : CHA-SVMAK01
TimeStamp : 11/2/2010 7:45:29 AM
FullName : Microsoft.Practices.EnterpriseLibrary.ExceptionHandling, Version=4.0.0.0, Culture=neutral, PublicKeyToken=null
AppDomainName : /LM/W3SVC/1/Root/Odms-1-129331554544329397
ThreadIdentity : 
WindowsIdentity : NT AUTHORITY\NETWORK SERVICE
 Inner Exception
 ---------------
 Type : System.UnauthorizedAccessException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
 Message : Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
 Source : 
 Help link : 
 Data : System.Collections.ListDictionaryInternal
 TargetSite : 
 Stack Trace : The stack trace is unavailable.
Category: General
Priority: 0
EventId: 100
Severity: Error
Title:Enterprise Library Exception Handling
Machine: CHA-SVMAK01
Application Domain: /LM/W3SVC/1/Root/Odms-1-129331554544329397
Process Id: 992
Process Name: c:\windows\system32\inetsrv\w3wp.exe
Win32 Thread Id: 5512
Thread Name: 
Extended Properties: 
----------------------------------------

I'm confused getting this exception, Can any one of you help me out of this issue. My IIS 6 in windows server 2003 has anonymous access enabled. It would be highly helpful if any one can help me resolving this issue. I've been trying for long but couldn't figure out yet. Thanks in advance.
Regards,
Subhadeep