Question

Suppose I’m querying a table, and null might be one of the values to look for. A query that’s set up like this

command.CommandText = "select * from People where Saluation = @salutation";

if(salutation != null) command.Parameters.AddWithValue("@salutation", salutation);
else command.Parameters.AddWithValue("@salutation", DBNull.Value);

won’t return any results when salutation is null. So I’m inclined to do this instead, but it feels ugly to me:

string whereClause;
if(!string.IsNullOrEmpty(salutation))
{
    whereClause = "Salutation = @salutation";
    command.Parameters.AddWithValue("@salutation", salutation);
}
else whereClause = "Salutation is null";

command.CommandText = "select * from People where " + whereClause;

Is there a more correct way?

Answer 1

I would probably avoid concatenation to build your where clause. You could change you sql to the following. May open your self up for SQL Injections attacks.

command.CommandText = "select * from People where (@salutation is null and salutation is null) or Saluation = @salutation";