SQL Query not working due to Foreign Key - asp.net

Question

I have two tables for a hospital system
patient
(PK) ID - int (auto increments)
Name -varchar
surname -varchar
DOB - varchar
Email- varchar
Phone -varchar
(FK)address_ID
and
address table
Address(ID)-int (auto increment)
Line1 - varchar
Line2 - varchar
city - varchar
state - varchar
everytime I try and register a new patient, it doesn't include Address ID in the patient table. I have it address table and address_id linked to the patient table for address_ID in the database diagram as its foreign key, it keeps giving me an error saying its null. So if it doesn't automatically go in the patient table how do I auto increment it so that it stays the same as the address_ID in the address table?
This is the code I'm using to insert the values from the form.
string query1 = "insert into patient(name,surname,dob,email,phone) values (#pname, #psurname, #pdob, #pemail, #pphone)";
string query2 = "insert into patient_address(Line1,Line2,city,state) values (#pline1, #pline2, #pcity, #pstate)";
SqlCommand cmd1 = new SqlCommand(query1, con);
cmd1.Parameters.AddWithValue("#pname", pname.Text);
cmd1.Parameters.AddWithValue("#psurname", psurname.Text);
cmd1.Parameters.AddWithValue("#pdob", dob.SelectedValue);
cmd1.Parameters.AddWithValue("#pemail", pemail.Text);
cmd1.Parameters.AddWithValue("#pphone", pphone.Text);
SqlCommand cmd2 = new SqlCommand(query2, con);
cmd2.Parameters.AddWithValue("#pline1", pline1.Text);
cmd2.Parameters.AddWithValue("#pline2", pline2.Text);
cmd2.Parameters.AddWithValue("#pcity", pcity.Text);
cmd2.Parameters.AddWithValue("#cstate", pstate.SelectedValue);
con.Open();
cmd2.ExecuteNonQuery();
cmd1.ExecuteNonQuery();
con.Close();
If anyone could offer some kind of guidance it would be helpful! Thanks.

Answer 1

The address_ID is a (FK) can be Null or Not Null (you may check if it's allow to accept null or not (null-able or not), so check if (FK) accept to be null or not
In the 1:N relation:
If the (FK) is accept to be null some times, that mean some of patients here do not have an address (so it's not required).
But if the (FK) is not accept to be null, so all the patients should have an address, and it should not be null.
And the (PK) should not be null at all.
So in your case I think the simplest way to add a custom constraints
or add one extra column (IsAdressExist) to the patient table,
or simply first add an addition row in the address_table which will refer to (empty address with Address(ID)=-1 for example), then set the default value for the patients that do not have an address with (FK)address_ID =-1
or just set the Address(ID_FK) Default Value or Binding as a (NULL)
If you want to add a new address to the address table and you need to use the same new address to be FK to the patient table, so you need to (the simplest way):
1- Add the new address to the address table.
2- Get the MAX Address_ID (PK) from the address table
3- Use that max address_ID and insert it to the patient table as FK.
OR
You need to create one long query that will do the same previous steps that I mentioned above.