Simple Async HTTP Request

by Manuel 7/24/2008 8:25:00 AM

Since .NET Framework 2.0 there is a very easy way to perform an asynchronous HTTP request and retrieve the result as a string.
The System.Net.WebClient class provides methods and events to handle this task in a very convenient way:

using System.Net;

private void Button_Click(object sender, RoutedEventArgs e)
{
   string topic=this.SearchTextBox.Text;
   string url = "http://yourserver.com";
   WebClient client = new WebClient();
   client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);
   client.DownloadStringAsync(new Uri(url));
}

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
   if (e.Error == null)
   {
      string result = e.Result;
   }
}

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C# | ASP.NET

Switching the current asp.net user account programmatically

by Manuel 12/13/2007 9:51:00 AM

Sometimes it is necessary to change the user under whose account asp.net runs to execute a special method. This could be the case e.g. if you want to access an ADS with a local asp.net user and you get an error message "invalid username or password" (there is the possibility to pass a username and passwort, but that didn't work for me).

The usage of the class below is very simple:

...
Impersonation imp = new Impersonation();
imp.ImpersonateValidUser("username", "domain", "password");
//execute your work here
imp.UndoImpersonation();
....

using System;
using System.Security.Principal;
using System.Runtime.InteropServices;

namespace Security
{

   public class Impersonation
   {

      public const int LOGON32_LOGON_INTERACTIVE = 2;
      public const int LOGON32_PROVIDER_DEFAULT = 0;
      WindowsImpersonationContext impersonationContext;

      [DllImport("advapi32.dll")]
      public static extern int LogonUserA(String lpszUserName,
         String lpszDomain,
         String lpszPassword,
         int dwLogonType,
         int dwLogonProvider,
         ref IntPtr phToken);

      [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
      public static extern int DuplicateToken(IntPtr hToken,
         int impersonationLevel,
         ref IntPtr hNewToken);

[DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
public static extern bool RevertToSelf();

[DllImport("kernel32.dll", CharSet=CharSet.Auto)]
public static extern bool CloseHandle(IntPtr handle);

      public bool ImpersonateValidUser(String userName, String domain, String password)
      {
         WindowsIdentity tempWindowsIdentity;
         IntPtr token = IntPtr.Zero;
         IntPtr tokenDuplicate = IntPtr.Zero;

         if(RevertToSelf())
         {
            if(LogonUserA(userName, domain, password, LOGON32_LOGON_INTERACTIVE,
               LOGON32_PROVIDER_DEFAULT, ref token) != 0)
            {
               if(DuplicateToken(token, 2, ref tokenDuplicate) != 0)
               {
                  tempWindowsIdentity = new WindowsIdentity(tokenDuplicate);
                  impersonationContext = tempWindowsIdentity.Impersonate();
                  if (impersonationContext != null)
                  {
                     CloseHandle(token);
                     CloseHandle(tokenDuplicate);
                     return true;
                  }
               }
            }
         }          if(token!= IntPtr.Zero) CloseHandle(token);
         if(tokenDuplicate!=IntPtr.Zero) CloseHandle(tokenDuplicate);
         return false;
      }

      public void UndoImpersonation()
      {
         impersonationContext.Undo();
      }

   }
}

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Tags: impersonation, permissions, security

C# | ASP.NET

How to provide data global during a request (or where is the request context?) (ASP.NET)

by Manuel 12/13/2007 9:40:00 AM

You can save your data during a HttpRequest by passing it to System.Web.HttpContext.Current.Items[itemKey].
Objects stored in this Collection will be available during the whole lifecycle of the HttpRequest.

Example of usage:

System.Web.HttpContext.Current.Items["reloadCount"] = 5;

int reloadCount = (int) System.Web.HttpContext.Current.Items["reloadCount"];

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Tags: httprequest

C# | ASP.NET

How to read and write a DataSet from and to XML (C#)

by Manuel 12/13/2007 9:38:00 AM

private DataSet ReadDataSet(string dataPath)
{
   DataSet ds = new DataSet();
   ds.ReadXml(dataPath, XmlReadMode.ReadSchema);
   return ds;
}

private void WriteDataSet(DataSet ds, string path)
{
   ds.WriteXml(path, XmlWriteMode.WriteSchema);
}

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Tags: dataset, xml

C# | ASP.NET

How to convert a comma seperated file (.csv) into a dataset (C#)

by Manuel 12/13/2007 9:35:00 AM

public DataSet GetCSVFile( string fileName)
{
     string pathName = System.IO. Path .GetDirectoryName(fileName);
     string file = System.IO. Path .GetFileName(fileName);
     OleDbConnection excelConnection = new OleDbConnection
     (@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+ pathName + ";Extended Properties=Text;");
     OleDbCommandexcelCommand = newOleDbCommand(@"SELECT * FROM "+ file, excelConnection);
     OleDbDataAdapterexcelAdapter = newOleDbDataAdapter(excelCommand);
     excelConnection.Open();
     DataSetds = newDataSet();
     excelAdapter.Fill(ds);
     excelConnection.Close();
     return ds;
}

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Tags: csv, dataset

C# | ASP.NET

global.asax events

by Manuel 12/6/2007 2:32:00 AM

HttpApplication Events:

Application_AcquireRequestState
Occurs when ASP.NET acquires the current state (for example, session state) that is associated with the current request.

Application_AuthenticateRequest
Occurs when a security module has established the identity of the user.

Application_AuthorizeRequest
Occurs when a security module has verified user authorization.

Application_BeginRequest
Occurs as the first event in the HTTP pipeline chain of execution when ASP.NET responds to a request.

Application_Disposed
Adds an event handler to listen to the Disposed event on the application.

Application_EndRequest
Occurs as the last event in the HTTP pipeline chain of execution when ASP.NET responds to a request.

Application_Error
Occurs when an unhandled exception is thrown.

Application_PostAcquireRequestState
Occurs when the request state (for example, session state) that is associated with the current request has been obtained.

Application_PostAuthenticateRequest
Occurs when a security module has established the identity of the user.

Application_PostAuthorizeRequest
Occurs when the user for the current request has been authorized.

Application_PostMapRequestHandler
Occurs when ASP.NET has mapped the current request to the appropriate event handler.

Application_PostReleaseRequestState
Occurs when ASP.NET has completed executing all request event handlers and the request state data has been stored.

Application_PostRequestHandlerExecute
Occurs when the ASP.NET event handler (for example, a page or an XML Web service) finishes execution.

Application_PostResolveRequestCache
Occurs when ASP.NET bypasses execution of the current event handler and allows a caching module to serve a request from the cache.

Application_PostUpdateRequestCache
Occurs when ASP.NET completes updating caching modules and storing responses that are used to serve subsequent requests from the cache.

Application_PreRequestHandlerExecute
Occurs just before ASP.NET begins executing an event handler (for example, a page or an XML Web service).

Application_PreSendRequestContent
Occurs just before ASP.NET sends content to the client.

Application_PreSendRequestHeaders
Occurs just before ASP.NET sends HTTP headers to the client.

Application_ReleaseRequestState
Occurs after ASP.NET finishes executing all request event handlers. This event causes state modules to save the current state data.

Application_ResolveRequestCache
Occurs when ASP.NET completes an authorization event to let the caching modules serve requests from the cache, bypassing execution of the event handler (for example, a page or an XML Web service).

Application_UpdateRequestCache
Occurs when ASP.NET finishes executing an event handler in order to let caching modules store responses that will be used to serve subsequent requests from the cache.

Application_Init
This method occurs after _start and is used for initializing code.

Application_Start
As with traditional ASP, used to set up an application environment and only called when the application first starts.

Application_End
Again, like classic ASP, used to clean up variables and memory when an application ends.

Session Events:

Session_Start
As with classic ASP, this event is triggered when any new user accesses the web site.

Session_End
As with classic ASP, this event is triggered when a user's session times out or ends. Note this can be 20 mins (the default session timeout value) after the user actually leaves the site.

Profile Events:

Profile_MigrateAnonymous
Occurs when the anonymous user for a profile logs in.

Passport Events:

PassportAuthentication_OnAuthenticate
Raised during authentication. This is a Global.asax event that must be named PassportAuthentication_OnAuthenticate.

Possibly more events defined in other HttpModules like:

System.Web.Caching.OutputCacheModule
System.Web.SessionState.SessionStateModule
System.Web.Security.WindowsAuthentication
System.Web.Security.FormsAuthenticationModule
System.Web.Security.PassportAuthenticationModule
System.Web.Security.UrlAuthorizationModule
System.Web.Security.FileAuthorizationModule
System.Web.Profile.ProfileModule

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C# | ASP.NET

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The Better Blog

News, Tips, Tricks and Stuff by Manuel Trunk

Simple Async HTTP Request

Switching the current asp.net user account programmatically

How to provide data global during a request (or where is the request context?) (ASP.NET)

How to read and write a DataSet from and to XML (C#)

How to convert a comma seperated file (.csv) into a dataset (C#)

global.asax events

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