How to handle sqlcommand parameter that could be null?

I have this sql sqlcommand:

string sql = "INSERT Zones (ZName, TypeID, Description) VALUES (@dotnet.itags.org.ZName, @dotnet.itags.org.typeID, @dotnet.itags.org.description)";

command.Parameters.Add("@dotnet.itags.org.description", SqlDbType.NVarChar, 100).Value = description;

The column Description is nullable. But if the variable description is null, it seems the paramter @dotnet.itags.org.description can't be passed correctly.

How can I pass a null parameter to sql server?

Thanks!

You can send DBNull.Value as a value, that is it.