Net6 project using AspNetCore framework

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Mark Bishop

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Nov 24, 2023, 5:42:05 AM11/24/23

to Excel-DNA

Hi Govert,

Is it possible to use the AspNetCoreFramework within a project? (I want to have a simple api listener running in the background for remote control purposes)

If i try and use any code that references Microsoft.AspNetCore, then I get the message:

System.IO.FileNotFoundException: 'Could not load file or assembly 'Microsoft.AspNetCore, Version=6.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60'. The system cannot find the file specified.'

I tried to add the reference libraries as references to be included in dna file but the loader rejected them as they are ref libraries.

Is there another way to do this?

thanks

Govert van Drimmelen

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Dec 12, 2023, 3:50:33 AM12/12/23

to Excel-DNA

If you just want a simple http server in your add-in, I don't need ASP.NET and can just use the HttpListener class that is part of the core runtime.

Code for this might be:

using System.Net;
using System;
using ExcelDna.Integration;

namespace TestAspNetInExcel
{
public class AddIn : IExcelAddIn
{
public static object SayHello() => "Hello from ExcelDna with ASP.NET!";

public void AutoOpen()
{
Task.Run(() => StartHttpListener());
}

public void AutoClose()
{
}

async void StartHttpListener()
{
HttpListener listener = new HttpListener();
listener.Prefixes.Add("http://localhost:8000/");
listener.Start();

while (true)
{
HttpListenerContext context = await listener.GetContextAsync();
HttpListenerResponse response = context.Response;

string responseString = "<html><body>Hello, World!</body></html>";
byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString);

response.ContentLength64 = buffer.Length;
System.IO.Stream output = response.OutputStream;
await output.WriteAsync(buffer, 0, buffer.Length);
output.Close();
}
}
}
}

Using more of the ASP.NET functionality won't work at the moment, because of the way Excel-DNA is setting up the runtime loading.

When loading the runtime for the first time, we create a fresh .runtimeconfig.json that just loads the "Microsoft.WindowsDesktop.App" framework.

For ASP.NET support, you also need the "Microsoft.AspNetCore.App" framework loaded at runtime startup.

Excel-DNA could be enhanced to add this as an option when loading the runtime, though it would only work if this add-in is the first one to load into Excel.

I'm not sure that's the right approach though, given that the Excel process might need to host various add-ins.

If you only need a bit more help than the basic HttpListener support, you might look at one of the lightweight wrappers around HttpListener that would just add a library or two to your add-in.

If you really need full ASP.NET support, we would need to make some changes on the Excel-DNA side.