DateTime columns cause schema type lookups to fail in DataFrame

[WalternativE]

System information

• OS version/distro: Windows 10 20H2 19042.844
• .NET Version (eg., dotnet --info): 5.0.200

Issue

• What did you do?
  I tried to use the Explore() and ExploreWithSandDance() extension methods on the
  IDataView type of the underlying DataFrame which contained a column of the type
  PrimitiveDataFrameColumn<DateTime>.

• What happened?
  I received the following error

  Error: System.NotSupportedException: Specified method is not supported.
  at Microsoft.Data.Analysis.PrimitiveDataFrameColumn`1.GetDataViewType()
  at Microsoft.Data.Analysis.PrimitiveDataFrameColumn`1.AddDataViewColumn(Builder builder)
  at Microsoft.Data.Analysis.DataFrame.get_DataViewSchema()
  at Microsoft.ML.DataViewExtensions.ToTabularJsonString(IDataView source)
  at Microsoft.ML.DataViewExtensions.ExploreWithSandDance(IDataView source)
  at <StartupCode$FSI_0011>.$FSI_0011.main@()
  

• What did you expect?
  I expected the same behavior as when I tried the same procedure with a DataFrame which did not contain a
  DateTime column.

Source code / logs

As explained above I received a NotSupportedException. I assume, that it is connected to the execution of this line
source.Schema.ToDictionary(column => column.Name, column => column.Type.RawType); in the extension method to create the TabularJsonObject here.

I created a notebook which showcases how I stumbled upon the error. It should be possible to use the binder link in the readme for this, even though it botches up the last redirect for some reason.

[eerhardt]

cc @pgovind

[dazinator]

Just hit this exception trying to follow the sample here with my own csv file: https://github.com/dotnet/interactive/blob/main/samples/ExtensionLab/ExtensionLab-SandDance.ipynb

[eerhardt]

FYI - @dakersnar

[michaelgsharp]

@JakeRadMSFT is this something you guys are working on fixing?

[beccamc]

This is fixed. I've confirmed that with a PrimitiveDataFrameColumn<DateTime> you can ExploreWithSandDance()

If anyone sees any other problems here please reach out.