As I told you when I answered this question yesterday:
Two problems here:
1) Either one of your names is wrong: "txtEmpid", "txtName", or "txtEmailid" is incorrect, or one of them is not a textbox. This means that the "tn" variable gets a null, so you get the error when you try to use it's Text property. Check the names and types.
2) Do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead. This is particularly a problem with website code, where your database can be deleted from the other side of the world...
Please do not re-post the same question.
Object reference not set to an instance of an object.[
^]