Just a missing a line in your code...
DataRow row = patient.Tables["Patient"].NewRow();
row[0] = hno;
row[1] = fname;
row[2] = lname;
row[3] = pnum;
row[4] = address;
row[5] = email;
patient.Tables["Patient"].Rows.Add(row); // <- Add the row to the collection
sqladapter.Update(patient, "Patient");