records are duplicated in sql server

Hi,

One thing is clear it is not a problem of sql server. Its saves what you are providing. Recheck your code and store procedure that saves your records. Recheck and redefine the keys and constraint of your table.

Actually, unlike everyone else here, I believe your issue is with the database, and here is why.

Any insert to a table, especially tables containing financial information, need to be protected and validated properly.

Inserts on tables like this should always go through a stored procedure so that the data can be validated as unique before it gets into the table as a duplicate. If the record that is trying to get inserted is found to be a potential duplicate, it should get written to a suspect record table which can then be manually reviewed so that if it is indeed valid, it can be transferred to the appropriate place.

Sandeep's answer is correct in that there is a refresh page issue in asp.net and that it could be a potential issue, but you should never, ever rely on the UI portion of an application to protect your data.

It does not sound an issue of SQL Server. Surely the insertion is being trigger more than once from frontend only. One such scenario I can tell you is of pressing 'Refresh' button of browser or pressing a F5 button.
In this case, the same events would be triggered and data can be duplicated. Check if that's the case. If so, have a look at this article to workaround it: Refresh Page Issue in ASP.Net[^]