Additional information: Procedure or function 'spCustomerRegistration' expects parameter '#other', which was not supplied - sql

Question

I am trying to insert data into an MS SQL database table and gets this error when the other field is empty
The Other Column has Allow Nulls set to true
Additional information: Procedure or function 'spCustomerRegistration' expects parameter '#other', which was not supplied.
Model Code
SqlCommand cmd = new SqlCommand("spCustomerRegistration", con);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("#firstname", txtFirstName);
cmd.Parameters.AddWithValue("#lastname", txtLastName);
cmd.Parameters.AddWithValue("#stateid", ddLocation1);
cmd.Parameters.AddWithValue("#urbanrural", txtStatUR);
cmd.Parameters.AddWithValue("#cityid", city_id);
cmd.Parameters.AddWithValue("#areaid", area_id);
cmd.Parameters.AddWithValue("#streetid", street_id);
cmd.Parameters.AddWithValue("#townid", town_id);
cmd.Parameters.AddWithValue("#villageid", village_id);
cmd.Parameters.AddWithValue("#houseno", txtHouseNo);
cmd.Parameters.AddWithValue("#dob", Convert.ToDateTime(DOB));
cmd.Parameters.AddWithValue("#customeremail", txtEmail);
cmd.Parameters.AddWithValue("#customerphone", _phone_number);
cmd.Parameters.AddWithValue("#gender", ddGender);
cmd.Parameters.AddWithValue("#password", dal.Encryptdata(txtPassword));
cmd.Parameters.AddWithValue("#customeripaddress", _cip);
cmd.Parameters.AddWithValue("#regcode", _regcode);
cmd.Parameters.AddWithValue("#customerguid", _CustomerGuid);
cmd.Parameters.AddWithValue("#other", txtOthers);
cmd.Parameters.Add("#retval", SqlDbType.Int);
cmd.Parameters["#retval"].Direction = ParameterDirection.Output;
cmd.Parameters.Add("#userid", SqlDbType.Int, 0, "id");
cmd.Parameters["#userid"].Direction = ParameterDirection.Output;
con.Open();
cmd.ExecuteNonQuery();
retval = (int)cmd.Parameters["#retval"].Value;
pk_uid = (int)cmd.Parameters["#userid"].Value;
con.Close();
Stored Procedure
BEGIN
SET NOCOUNT ON;
IF NOT EXISTS(SELECT * FROM CustomerRegistration WHERE CustomerEmail =#customeremail or CustomerPhone=#customerphone )
BEGIN
INSERT INTO CustomerRegistration (FirstName ,LastName ,StateID, Urban_Rural, CityID, AreaID, StreetID, TownID, VillageID, HouseNo, DOB, CustomerEmail, CustomerPhone, Gender, Password, CustomerIPAddress, RegCode, CustomerGuid, Other ) VALUES (#firstname, #lastname, #stateid, #urbanrural, #cityid, #areaid, #streetid, #townid, #villageid, #houseno, #dob, #customeremail, #customerphone, #gender, #password, #customeripaddress, #regcode, #customerguid, #other )
SELECT #userid = SCOPE_IDENTITY();
SET #retval=1
END
ELSE
BEGIN
SET #retval =0
SET #userid =0
END

Answer 1

Sql server does not support null. when any object or value is null then you have to assign value DBNull.Value instead of null.