paypal donation button integraion in asp.net c#

To create a Sandbox test account:
Go to https://developer.paypal.com/.
Click "Sign Up Now."
Complete the form and accept the Terms of Use.
Click "Sign Up."
Once you complete the sign up, create a test account:
Log in at https://developer.paypal.com/.
Click the "Test Accounts" link.
Click the "Create Test Account" link.
Complete the form and click "Create Account."
For more information, see the Sandbox User Guide:
From your Sandbox account, click "Help."
Click the "Sandbox User Guide (PDF)" link
To view your Sandbox emails, please follow the steps below:
Log in to Developer Central at https://developer.paypal.com
Click the 'Email' tab on the left side.
Your Sandbox generated emails can be found on this page
For more information, please refer to the API Sandbox User Guide, pp 15-16.
Please follow the steps below to generate a credit card number for testing PayPal Account Optional within the Sandbox.
Log in to your Sandbox Account
Click 'Profile'
Click on 'Credit Cards' under Financial Information
Click the ''Add' button, as if you are adding a credit card to the account
Use the credit card number that is automatically generated here as the credit card of your buyer
Note: Do not click on the 'Add Card' button as this will add the credit card to your Sandbox account. If it is added to your Sandbox account, it cannot be used to make a non-PayPal account payment.
For a Social Security Number within the Sandbox, you can enter a number beginning with 111 and then enter random numbers.  To get a Social Security Number generated for your account, go to your Account Overview page and click on the 'Money Market' link, then click on 'Enroll Now'.  This will generate a SSN for your account that you can copy and use for your Sandbox account.