System.Data.SqlClient.SqlException: Login failed for user 'IIS APPPOOL\DefaultAppPool' in IIS7

Introduction:

In this article I will explain how to solve System.Data.SqlClient.SqlException: Login failed for user 'IIS APPPOOL\DefaultAppPool' problem in IIS7. 

Description: 

Recently I started working with IIS7 at that time I face some of strange problems to rectify those errors I did some modifications in IIS. After seen those errors I decided to write this post to help people who are need with this error.  I did one sample application and deploy application in IIS. I started running my deployed application at that time I get error like this 

System.Data.SqlClient.SqlException: Login failed for user 'IIS APPPOOL\DefaultAppPool'

To solve this problem I made modifications in IIS configuration to make those changes just follow below steps to solve this problem.

Start ---> Open Run and type inetmgr and click OK now our IIS will open

In IIS select Application Pools ---> In that select DefaultAppPool ---> Right Click on DefaultAppPool---> Select Advanced Settings

After open Advanced Settings one window will open in that select Identity and change path selection for Identity

Now change the Identity path selection from ApplicationPoolIdentity to LocalSystem

Select Built-in account to LocalSystem click OK now your problem will solve and it will work for you.