load in DataGrid general connection string C#

if(!Page.isPostBack())
{
string connectionstring =ConfigurationManager.ConnectionStrings["TestConnectionString"].ConnectionString;
SqlConnection myconnection = new mysqlconnection();
Dataset ds = new Dataset();
SqlAdapter as = new SqlAdapter("Select * from emp",MyConnection);
ds.fill(as);
Datagrid.Datasource= ds;
Datagrid.Databind();
}
if(!Ispostback)
{
String Connectionstring =(string)ConfigurationSection.AppSettings["ConnectionString"];
SqlConnection myconnection = new mysQlConnection();
sqlCommand cmd = new sqlcommand("select * from emp",Myconnection);
SqlDatareader dr = null;
dr = cmd.executereader();
datagrid.Datasource= dr;
datagrid.databind();



}