GetFieldType throws NotImplementedException, so the reader can't be used with Dapper

[jnm2]

We were hoping to use Dapper's dataReader.Parse<T>(); extension method, but Dapper calls IDataReader.GetFieldType and the current implementation crashes:

https://github.com/yellowfeather/DbfDataReader/blob/a68402cf31039807c834641012279d160a6aad8c/src/DbfDataReader/DbfDataReader.cs#L255-L258

This is the call stack from Dapper:

at DbfDataReader.DbfDataReader.GetFieldType(Int32 ordinal)
at Dapper.SqlMapper.GetColumnHash(IDataReader reader, Int32 startBound, Int32 length) in C:\projects\dapper\Dapper\SqlMapper.cs:line 41
at Dapper.SqlMapper.TypeDeserializerCache.GetReader(IDataReader reader, Int32 startBound, Int32 length, Boolean returnNullIfFirstMissing) in C:\projects\dapper\Dapper\SqlMapper.TypeDeserializerCache.cs:line 143
at Dapper.SqlMapper.TypeDeserializerCache.GetReader(Type type, IDataReader reader, Int32 startBound, Int32 length, Boolean returnNullIfFirstMissing) in C:\projects\dapper\Dapper\SqlMapper.TypeDeserializerCache.cs:line 50
at Dapper.SqlMapper.GetDeserializer(Type type, IDataReader reader, Int32 startBound, Int32 length, Boolean returnNullIfFirstMissing) in C:\projects\dapper\Dapper\SqlMapper.cs:line 1789
at Dapper.SqlMapper.GetRowParser[T](IDataReader reader, Type concreteType, Int32 startIndex, Int32 length, Boolean returnNullIfFirstMissing) in C:\projects\dapper\Dapper\SqlMapper.IDataReader.cs:line 142

Would you take a pull request to implement GetFieldType?

It looks the implementation could be something like a switch on DbfTable.Columns[ordinal].ColumnType similar to the switch in DbfRecord.CreateDbfValue.

[chrisrichards]

A PR would be great, thanks! I wonder if it would be better to add something like Type GetType() to IDbfValue and the implementations of DbfValue

[jnm2]

@chrisrichards Oh, interesting. Would that allow GetFieldType to work even if there are no values, e.g. when Read() has not yet been called or after Read() returns false?

[chrisrichards]

Yes it would, the values are created in the DbfRecord constructor before any records have been read

[chrisrichards]

Fixed by #49

[jnm2]

Nice, thank you for the fast release!