ArgumentException: Invalid destination prefix. (Parameter 'destinationPrefix')

[rubenc57]

Hello

I get this error after upgrading my webforms project, using .NET Upgrade Assistant

ArgumentException: Invalid destination prefix. (Parameter 'destinationPrefix')

WebApp .net framework 4.8
to
WebAppCore .net 8.0

Yarp.ReverseProxy 2.1.0

Can someone knows why?

Greetings
Ruben

[MihaZupan]

The error indicates that the YARP configuration is incorrect - the destination wasn't configured with a proper address (e.g. it was an empty string).

Can you check that ProxyTo is configured correctly in your launchSettings.json / appsettings.json?
You can also print app.Configuration["ProxyTo"] to see what the value was set to at runtime.

[rubenc57]

appsettings.json
...
"AllowedHosts": "*",
"ProxyTo": ""

program.cs
...
app.MapForwarder("/{**catch-all}", app.Configuration["ProxyTo"]).Add(static builder => ((RouteEndpointBuilder)builder).Order = int.MaxValue);

---

var men = app.Configuration["ProxyTo"];
returns an empty value.

[rubenc57]

Ok

The problem was on the launchSettings.json file

The "ProxyTo" was not defined

Problem fixed

Thank you