Skip to main content

ASP.NET Core - ActionResult doesn’t work with IList

I’m currently rewriting an existing ASP.NET Web API application to ASP.NET Core. Yesterday I blogged about the use of the ActionResult<T> to combine the type safety of typed controllers with the list of out-of-the-box actionresults.

While introducing the ActionResult<T> class everywhere, I stumbled over one use case where I got a compiler error. Here is the specific code:

When you try to compile this code in Visual Studio it fails with the following error message:

CS0029: Cannot implicitly convert type ‘System.Collection.Generic.IList<T> to Microsoft.AspNetCore.Mvc.ActionResult<System.Collection.Generic.IList<T>>.

The reason is because C# doesn't support implicit cast operators on interfaces. Consequently, we need to convert the interface to a concrete type if we want to use it as our type argument for ActionResult<T>.

An easy fix is to wrap the IList in a concrete type as I did in the example below:

Labels:

Popular posts from this blog

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

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

DevToys–A swiss army knife for developers

As a developer there are a lot of small tasks you need to do as part of your coding, debugging and testing activities.  DevToys is an offline windows app that tries to help you with these tasks. Instead of using different websites you get a fully offline experience offering help for a large list of tasks. Many tools are available. Here is the current list: Converters JSON <> YAML Timestamp Number Base Cron Parser Encoders / Decoders HTML URL Base64 Text & Image GZip JWT Decoder Formatters JSON SQL XML Generators Hash (MD5, SHA1, SHA256, SHA512) UUID 1 and 4 Lorem Ipsum Checksum Text Escape / Unescape Inspector & Case Converter Regex Tester Text Comparer XML Validator Markdown Preview Graphic Col...
Read more