Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.

Hi,

   Check whether that update statement is correct.

If it is correct and if it takes so long time to execute use

cmd.CommandTimeout = 0 after cmd.ExecuteNonquery() statement.

usually it takes maximum 30 seconds to execute the query if that time cross then this type of error will appear. So if it is a large statement and has bunch of records update use cmd.commandTimeout = 0 it takes unlimited time to execute.