Skip to main content

ASP.NET Core Configuration - System.ArgumentException: Item has already been added.

In ASP.NET Core you can specify an environment by setting the 'ASPNETCORE_ENVIRONMENT'  environment variable on your server. Yesterday however I wanted to setup a second environment on the same machine. To achieve this I added a second website to IIS and set the environment variable through a parameter in my web.config:

<aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" forwardWindowsAuthToken="false" stdoutLogEnabled="false" startupTimeLimit="3600" requestTimeout="23:00:00">
<environmentVariables>
<environmentVariable name="ASPNETCORE_ENVIRONMENT" value="Test" />
</environmentVariables>
</aspNetCore>
view raw web.config hosted with ❤ by GitHub

Unfortunately after doing that my application no longer worked. In the Event Viewer I could see the following error message:

Application: dotnet.exe

CoreCLR Version: 4.6.26628.5

Description: The process was terminated due to an unhandled exception.

Exception Info: System.ArgumentException: Item has already been added. Key in dictionary: 'ASPNETCORE_ENVIRONMENT'  Key being added: 'ASPNETCORE_ENVIRONMENT'

   at System.Collections.Hashtable.Insert(Object key, Object nvalue, Boolean add)

   at System.Environment.ToHashtable(IEnumerable`1 pairs)

   at System.Environment.GetEnvironmentVariables()

   at Microsoft.Extensions.Configuration.EnvironmentVariables.EnvironmentVariablesConfigurationProvider.Load()

   at Microsoft.Extensions.Configuration.ConfigurationRoot..ctor(IList`1 providers)

   at Microsoft.Extensions.Configuration.ConfigurationBuilder.Build()

   at Microsoft.AspNetCore.Hosting.WebHostBuilder..ctor()

   at Web.Program.Main(String[] args) in c:\Program.cs:line 10

It seems that ASP.NET Core doesn’t like that you try to set the same variable twice. Strange because I thought it worked on a previous version of .NET Core(I’m running on 2.1at the moment).

To fix it, I had to remove the environment variable from the system(restart the system) and set the environment for all applications through the web.config.

Anyone with a better solution?

Labels

Labels:

Popular posts from this blog

Kubernetes–Limit your environmental impact

Reducing the carbon footprint and CO2 emission of our (cloud) workloads, is a responsibility of all of us. If you are running a Kubernetes cluster, have a look at Kube-Green . kube-green is a simple Kubernetes operator that automatically shuts down (some of) your pods when you don't need them. A single pod produces about 11 Kg CO2eq per year( here the calculation). Reason enough to give it a try! Installing kube-green in your cluster The easiest way to install the operator in your cluster is through kubectl. We first need to install a cert-manager: kubectl apply -f https://github.com/cert-manager/cert-manager/releases/download/v1.14.5/cert-manager.yaml Remark: Wait a minute before you continue as it can take some time before the cert-manager is up & running inside your cluster. Now we can install the kube-green operator: kubectl apply -f https://github.com/kube-green/kube-green/releases/latest/download/kube-green.yaml Now in the namespace where we want t...
Read more

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.
Read more

.NET 9 - Goodbye sln!

Although the csproj file evolved and simplified a lot over time, the Visual Studio solution file (.sln) remained an ugly file format full of magic GUIDs. With the latest .NET 9 SDK(9.0.200), we finally got an alternative; a new XML-based solution file(.slnx) got introduced in preview. So say goodbye to this ugly sln file: And meet his better looking slnx brother instead: To use this feature we first have to enable it: Go to Tools -> Options -> Environment -> Preview Features Check the checkbox next to Use Solution File Persistence Model Now we can migrate an existing sln file to slnx using the following command: dotnet sln migrate AICalculator.sln .slnx file D:\Projects\Test\AICalculator\AICalculator.slnx generated. Or create a new Visual Studio solution using the slnx format: dotnet new sln --format slnx The template "Solution File" was created successfully. The new format is not yet recognized by VSCode but it does work in Jetbr...
Read more