Reasons why ExcelDnaLoader might be throwing null object reference errors on registration all of a sudden?

[Bob Calco]

Hi Govert,

I have been happily implementing my UDFs, but suddenly on running in Excel the ExcelDnaLoader is blowing up at registration time. I have put breakpoints on all my UDFs to see if they're getting called (for some reason) but the breakpoints are never hit.

This is what's blowing up:

    member this.AutoOpen () =

      // The overload selection and delegate conversions performed by F# are not intuitive.

      let paramConvertConfig = 

        ParameterConversionConfiguration()

          .AddParameterConversion( 

            Func<Type, ExcelParameterRegistration, LambdaExpression>

              (FsParameterConversions.FsOptionalParameterConversion),

            null)

      ExcelRegistration.GetExcelFunctions ()

      |> fun fns -> ParameterConversionRegistration.ProcessParameterConversions (fns, paramConvertConfig)

      |> FsAsyncRegistration.ProcessFsAsyncRegistrations

      |> AsyncRegistration.ProcessAsyncRegistrations

      |> MapArrayFunctionRegistration.ProcessMapArrayFunctions

      |> ParamsRegistration.ProcessParamsRegistrations

      |> ExcelRegistration.RegisterFunctions

Specifically, it's blowing up at the last line, ExcelRegistration.RegisterFunctions.

What can I do to troubleshoot this? This new behavior was unexpected.

Sincerely,

Bob

[Bob Calco]

Sorry, I meant also to include a copy of the exception:

System.NullReferenceException

  HResult=0x80004003

  Message=Object reference not set to an instance of an object.

  Source=ExcelDna.Loader

  StackTrace:

   at ExcelDna.Loader.XlMethodInfo.ConvertToXlMethodInfos(List`1 methods, List`1 targets, List`1 lambdaExpressions, List`1 methodAttributes, List`1 argumentAttributes)

   at ExcelDna.Loader.IntegrationHost.RegisterLambdaExpressionsWithAttributes(List`1 lambdaExpressions, List`1 functionAttributes, List`1 argumentAttributes)

   at ExcelDna.Registration.ExcelRegistration.RegisterFunctions(IEnumerable`1 registrationEntries)

   at VisualScheme.AddIn.AddInFunctions.ExcelDna.Integration.IExcelAddIn.AutoOpen() in <path-to-my-add-in>\AddInFunctions.fs:line 36

Any suggestions how to sleuth this appreciated.

[Bob Calco]

OK, it seems be one of the libraries I'm calling, which has exhibited this behavior before, but I thought was fixed. I am instantiating a singleton object that uses it, and it's throwing the error. When I comment out the code in my UDF that makes a reference to the singleton object, then it loads as it's supposed to. So, I have to take this up with someone else. :)

[Greg Stevenson]

Hi there, 

We are running into a similar issue as above. I see no other responses to these posts. Could you share what you did to fix this problem? Thanks!