ado.net - 为什么 reader.GetOrdinal("FieldName") 会抛出异常？

Question

当字段不存在时，这会引发异常：

reader.IsDbNull(reader.GetOrdinal("FieldName"))=> 砰

为什么不返回 -1 ？

Answer 1

I'll try to guess here.

The common pattern for this method is to call GetOrdinal for column name and then call GetXXX() methods with given ordinal which is faster than do a search by column's name every time.

Therefore in case of exception here we fail fast and we can't ignore it. Wihtout exception we will try to find a column that doesn't exist and then try to find a field by given ordinal (without checking for -1 which is very easy to omit in this case) and only here we will realise that something went wrong few steps before (may be even too many steps before).