Top 5 Issues in ASP.NET applications.

I am going to figure out some common issue which is faced by almost every asp.net developer and still these issuese are going on and on. If you google with these issues you will find million of search results. Every technical forum will have atleast one thread related to these issues.

As a active member of asp.net forum, I have seen these issues being asked repeatedly. Lets have look on these issues. The first place goes to your favorite one :)

1. "Object reference not set to instance of object".
   This issue is most common issue in javascript as well as serverside code (VB,C#) and root cause for this issue could be anything , you need to explore it.
2. Second position goes to "Validation of viewstate MAC failed / The state information is invalid for this page and might be corrupted".
   There is one post on asp.net forum and it have total 10,088,223 views till 16th April 2013. So guess how many developers are facing this issue. You need to explore root cause for this issue.
3. "'Sys' is undefined"
   This is most common issue when you are using Ajax Control Toolkit. There is 4,959,577 views on asp.net forum as on 16th april 2013 for the thread related to this issue.
4. "Could not load file or assembly 'Microsoft.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified."
   Whenever you are opening older projects in new version of visual studio then you might see this issue. also there are many more cases in which you will get this error. It have total 4,290,920 views on asp.net forum as on 16th april 2013 . On asp.net forum you will find almost 100+ threads discussing about this issue and each thread has 2000000+ views. So you can imagine how frequently this or these type or errors are being faced by developers.
5. "Failed to execute request because the App-Domain could not be created. Error: 0x80070005 Access is denied. "
   This error occurs due to many reasons. There is not any single reason which can be explained but one may be due to folder access permission . You need to explore it more. For this issue total 112 experts provided their views and about 2,464,260 developers visited this thread but still it is unanswered.

So before starting any asp.net application, ready for facing these issues in your application. You need to explore the common cause of these issues. You may face these issue in your application and will try everything but it will not be resolved :).
If you have faced similar issues and still looking for solution then put your comments here, may be I can help to find out the solution. :P . Happy Koding