NativeAOT + Excel-DNA: functions with >16 parameters causing problems

[Melih Özcan KB01]

Hi, 

I have an Excel add-in implemented with ExcelDna, it works fine but I have a requirement to switch to NativeAOT compilation. When doing so, functions marked with [ExcelAsyncFunction] that have more than 16 parameters fail during the build.
The error:

error CS0305: Using the generic type 'Func<TResult>' requires 1 type arguments 
which points inside the file ExcelDna.SG.NAOT.Init.g.cs


As expected, this line in the generated file, points to sth. like this:
typeRefs.Add(typeof(Func<string, string, string, string, string, string, string, string, double, object?, object?, object?, object[,]?, object[,]?, object?, string?, string?, object?, object?, object>));

In order to get past the hard limit of 16 parameters, I tried to implement my own delegate types with the name Func in the System namespace as shown below:

namespace System
{

    public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, in T6, in T7, in T8, in T9, in T10, in T11, in T12, in T13, in T14, in T15, in T16, in T17, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7, T8 arg8, T9 arg9, T10 arg10, T11 arg11, T12 arg12, T13 arg13, T14 arg14, T15 arg15, T16 arg16, T17 arg17);

    public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, in T6, in T7, in T8, in T9, in T10, in T11, in T12, in T13, in T14, in T15, in T16, in T17, in T18, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7, T8 arg8, T9 arg9, T10 arg10, T11 arg11, T12 arg12, T13 arg13, T14 arg14, T15 arg15, T16 arg16, T17 arg17, T18 arg18);

    public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, in T6, in T7, in T8, in T9, in T10, in T11, in T12, in T13, in T14, in T15, in T16, in T17, in T18, in T19, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7, T8 arg8, T9 arg9, T10 arg10, T11 arg11, T12 arg12, T13 arg13, T14 arg14, T15 arg15, T16 arg16, T17 arg17, T18 arg18, T19 arg19);

    public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, in T6, in T7, in T8, in T9, in T10, in T11, in T12, in T13, in T14, in T15, in T16, in T17, in T18, in T19, in T20, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7, T8 arg8, T9 arg9, T10 arg10, T11 arg11, T12 arg12, T13 arg13, T14 arg14, T15 arg15, T16 arg16, T17 arg17, T18 arg18, T19 arg19, T20 arg20);

    public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, in T6, in T7, in T8, in T9, in T10, in T11, in T12, in T13, in T14, in T15, in T16, in T17, in T18, in T19, in T20, in T21, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7, T8 arg8, T9 arg9, T10 arg10, T11 arg11, T12 arg12, T13 arg13, T14 arg14, T15 arg15, T16 arg16, T17 arg17, T18 arg18, T19 arg19, T20 arg20, T21 arg21);
}

Upon doing so, I got past the build error, but this time when I start Excel with the add-in intact, it tells me :

Initialization [Error] Integration.DnaLibraryAutoOpen Error :
PlatformNotSupportedException - Operation is not supported on this platform.


Is there a way to get past this, or is there no way with the NAOT to have functions with more than 16 parameters?