Typecast any OleDbReader Double/Int16/Int32/Int64 to C# double?

Question

If I create a new OleDbReader as follows:

OleDbCommand command = new OleDbCommand(query, ActiveConnection);
reader = command.ExecuteReader();
while(reader.Read())
{
   someList.Add((double)reader["columnHeader"]);
}

How can I ensure that I'm always returned a double from the column specified, if the data returned is typed as Int16/Int32/Int64 instead of Double? Do I have to create a handler for each possible type? I know Double.Parse exists but it only accepts strings. So, while I could use ToString() beforehand I feel that this is probably not the most straightforward way to typecast.

Similarly, for another column, I wish to ensure that any String/Double/Int16/Int32/Int64 values return as strings. Will ToString() handle these cases?

I'm fine with potential overflow errors, as I'll check for exceptions regardless.

Answer 1

You should call Convert.ToDouble(), which has a handler for each type.

By contrast, ToString() will work for any non-null value. (as long as it overrides ToString(); all numeric types do)