Your INSERT statement is missing the names of the columns. Best practice is to include the names of the columns so that your SQL statements will work should someone later add one or more columns to the database table.
INSERT INTO EMPLOYEE (col1,col2,col3) Values(val1,val2,val3);
Also, when you put values directly from a TextBox into a SQL statement, your software is vulnerable to SQL Injection attacks. Best practice is to use SQLParameter Class to pass values to a parameterized SQL statement. It also performs better than when the variable value is embedded within the SQL statement.
INSERT INTO EMPLOYEE (col1,col2,col3) Values(@valName1,@valName2,@valName3);
Read this article: Use SQL Parameters to Overcome Ad Hoc Performance Issues