How to access files, folders and other local resources through .net

Applications these days may require to access local resources such as folders on disk, creating/deleting files, etc. I came across one such scenario wherein the application had to create a file on remote location and then periodically delete the file(2 days after file creation).

In this scenario, assume without the application in picture, an user creates a file. This seems pretty much simple though, but what I want to tell here is the sequence of events.

1. An user navigates to the location ( a folder on remote machine)
2. Create a file
3. Save the file.

These 3 events though straightforward, make an important assumption, and that is, the user is having access to create file.

When it comes to your .Net application, the application is running under the user of a lesser privilege (that's CAS for you) or Code Access Security. So most of the times it won't have the privilege to create a file.

To fix this either you have to grant the application account with the required privilege OR you can MAKE the application run on the privilege of a specific user.

So under which username does the .Net app really work ??-- Its Network Service for remote apps and ASPNET on local machines.

As discussed you can grant these users, depending on the scenario, access to the required folders and you're done. But theres a trap... All the .Net apps will now have access to this folder since all of them run by Network Service/ASPNET accounts.

It may happen that you have to restrict the access to such folders, then, you have only one option...execute the application under the context of a specific user who has access to only that location. To get this done, you need to explore WindowsImpersonation class. Below is the link with code sample

WindowsImpersonation class

With this class you can provide the username/password of the specific user account you want the application to execute and then reset the identity so that the rest of the application code works under the restricted .Net account.

Happy Coding :)

How to Format Date in CustomCalendarExtender control

The default date format for the CustomCalendarExtender is MM/dd/yyyy which is typically US date format. To change this format, you need to set the Format property of the control.

For UK based date format you can set this to dd/MM/yyyy which would display date as 19/03/2011 instead of 03/19/2011 (default format)


Happy Coding :)

Implementing Transactions in WCF

In synchronous communication (request-response-acknowledge) we generally refer to the response HTTP code to determine a successful transaction. But in some cases it might happen that an acknowledgement be sent to the server which will store this value in the database.

A typical scenario would be of file download process wherein the client needs to send the acknowledgement which stored in database for future use. For this you need to implement Transaction in WCF. To do this, you can use the TransactionScope class or you can use the OperationBehaviour attribute in WCF as below

[OperationBehavior(TransactionScopeRequired = true)]

This would require your web-method to execute as a part of transaction. Having done that, you can now return a Boolean value (True/False) as a result depending on the status of the download process. This value can then be stored in the database in Boolean/Bit format for future reference.

Happy Coding :)

Configuring your web application for Windows domain users

To provide authentication mechanism on Intranet websites is pretty easy. Use LDAP and all the users accessing your application on the Intranet get authenticated automatically. But how to achieve this in the internet scenario ??

It might happen that your application needs to be SCALABLE to allow your Windows domain users to access the website from internet. To achieve this, you just need to tweak the webconfig a bit with the entries shown below

Happy Coding :)

Solution for System.IO.IOException: The device is not ready. error

Many times our applications refer a file on disk. At the time of development, most of the developers refer to the file by it's absolute path.

The trap here is, the absolute path on the development environment most of the times differ from the path on the deployment server. So though you're able to build and ship the DLLs you will always encounter a runtime error. Thats simply because the AppDomain is not able to locate the file from the path you mentioned. Moreover, the path does not exist in itself :P

So to get rid of this scenario always use Server.MapPath which would resolve the file path on the server. Also refer the url below for code snippets.
Server.MapPath example

Happy Coding :)

How to use different target framework in Visual Studio 2010

In VS 2010 there is one beautiful feature wherein you can execute your legacy applications along with your new apps. This is possible because of the multi-targeting feature available in VS 2010.

Now you can decide which .Net Framework to use for your code through VS 2010.
Just Go to Solution Explorer -> Properties -> Build -> Target Framework.

You're done with it !!!

How to fetch value from dynamically created control

There are some cases wherein you can not create the controls to display data at compile time. For example, displaying values from a Hashtable in a TextBox control, you never know how many key-pairs you are going to deal with (provided the Hashtable contains dynamic data). The logic for displaying the data is pretty much simple. You create an array of TextBoxes or any other control to display the data and you are done with it.

But the main problem lies in fetching the data which might have got changed from the UI. If you try to find out the TextBox controls from Page.FindControl() you won't be able to do so, thats because there isn't any markup for the FindControl() to look for and thats why it will always be null.

So to tide over your problem you can simple fetch the value from just one line

Request.Form[yourcontrolID]

The Request object as we all know is base of the web architecture. So whatever is being communicated between client and a Server has to have its presence in the Request object. Technically speaking whatever controls you can find in the html markup of you page on the client side will be available in this Request object.

Happy Coding :)