Hello ,
you have not given any
Where
condition in your query . hence all rows are updated .
modified query will be like this
update Employee1 set EmployeeName=@PEmployeeId,EmployeeDesignation=@PEmployeeDesignation,EmployeeDOJ=@PEmployeeDOJ,EmployeeSalary=@PEmployeeSalary,EMployeeDepartmentno=@PEmployeeDepartmentno where EmployeeId=@PEmployeeId
thanks
animesh