I would like to add some null's to table:
command.CommandText =
"INSERT into clients (Addres, companyID) VALUES (@Addres, @companyID) ; select SCOPE_IDENTITY();";
command.Parameters.AddWithValue("@Addres", null);
command.Parameters.AddWithValue("@companyID", null);
Table dessign allows null's. Why I have this error then?
The parameterized query '(@Addres nvarchar(4000),@companyID nvarchar(4000))INSERT into cl' expects the parameter '@Addres', which was not supplied.
Use DBNull.Value instead.
command.Parameters.AddWithValue("@Addres", DBNull.Value);
command.Parameters.AddWithValue("@companyID", DBNull.Value);
You have to use DBNull class for null values in SQL. Your code will be like this:
command.Parameters.AddWithValue("@Addres", DBNull.Value);
command.Parameters.AddWithValue("@companyID", DBNull.Value);
You can use System.Data.SqlTypes.SqlString.Null
command.Parameters.AddWithValue("@Addres", System.Data.SqlTypes.SqlString.Null);
command.Parameters.AddWithValue("@companyID", System.Data.SqlTypes.SqlString.Null);
Read: Handling Null Values
DBNull.Value can be used for any type as opposed to SqlTypes.
It can be handy to make the code more readable and type-safe, for example:
var addrVal = new System.Data.SqlTypes.SqlString(someAddress);
// ...
if (condition) addrVal = System.Data.SqlTypes.SqlString.Null;
command.Parameters.AddWithValue("@Addres", addrVal);
nvarchar, that's why i have used it. If it's an int(for example): SqlInt32.Null. It's the "type safe" version.