TextLoader().CreateFrom() Unhandled Exception for version 0.2.0

[helloguo]

System information

• OS Windows 10:
• .NET Version 2.1.300-rc1-008673:

Issue

• What did you do?

I move my code from ML.NET version 0.1.0 to ML.NET version 0.2.0. I have a data structure FlightData looks like following. Then I use pipeline.Add(new TextLoader(trainingDataSet).CreateFrom<FlightData>(useHeader: true, separator: ',', allowQuotedStrings:true)); to load the data.

    public class FlightData
    {
        [Column(ordinal: "0")]
        public float QUARTER;
        [Column(ordinal: "1")]
        public float MONTH;
        [Column(ordinal: "2")]
        public float DAY_OF_MONTH;
        [Column(ordinal: "3")]
        ....
    }

• What happened?

Error message:

Unhandled Exception: System.InvalidOperationException: DAY_OF_MONTH is not alphanumeric.
   at Microsoft.ML.Data.TextLoader.CreateFrom[TInput](Boolean useHeader, Char separator, Boolean allowQuotedStrings, Boolean supportSparse, Boolean trimWhitespace)

After looking at the error msg and ML.NET source code https://github.com/dotnet/machinelearning/blob/master/src/Microsoft.ML/Data/TextLoader.cs#L87, I change DAY_OF_MONTH to DAYOFMONTH. Then the error disappears. But it's common to use _ in the variable names.

• What did you expect?

I can use _ in variable names, which are part of Input fed to TextLoader.

Source code / logs

Please paste or attach the code or logs or traces that would be helpful to diagnose the issue you are reporting.