Question

I have a security_role_cd column in database of smallint datatype. I am selecting this column using following code into a nullable int variable.

I am getting following error:

Error 3 Type of conditional expression cannot be determined because there is no implicit conversion between ‘null’ and ‘short’

What is the correct code to overcome this error?

SELECT R.security_role_cd  FROM Security_Role R WHERE security_role_name = 'Admin'

C#

        int? roleID = null;
        string commandText = "SELECT R.security_role_cd  FROM Security_Role R WHERE security_role_name = @roleName";
        SqlCommand command = new SqlCommand(commandText, connection);
        command.CommandType = System.Data.CommandType.Text;
        command.Parameters.AddWithValue("@roleName",roleName);
        SqlDataReader readerRole = command.ExecuteReader();
        if (readerRole.HasRows)
        {
            while (readerRole.Read())
            {
                roleID = readerRole.GetInt16(0) == 0 ? null : readerRole.GetInt16(0) ;

            }
        }
        readerRole.Close();

Answer 1

It just needs to know how to type the null:

roleID = readerRole.GetInt16(0) == 0 ? (int?)null : (int)readerRole.GetInt16(0);

Personally I’d cache the value though:

int tmp = readerRole.GetInt16(0); // implicit widening to int here
roleID = tmp == 0 ? (int?)null : tmp;

Although I’d also call into doubt the wisdom of turning a 0 into a null – better to use IsDBNull – something like:

if(reader.IsDBNull(0)) {
    roleID = null;
} else {
    roleID = (int)readerRole.GetInt16(0);
}