ASP.NET Core docker build error

Make sure to choose the correct OS when you Enable docker support:

Your docker daemon has to target Linux containers as well.

Well basically the answer of Celestin Bochis and Pavel Agarkov are great. However since .net core 2.2 at least, the os of docker is stored in the .csproj file.

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp2.2</TargetFramework>
    <DockerDefaultTargetOS>Linux</DockerDefaultTargetOS>
    ...
   </PropertyGroup>

   ...
</Project>

And also don't forget to modify your docker file. The images should be the correct one. For .net core 2.2 That is :

Linux:
Microsoft/dotnet:2.2-aspnetcore-runtime AS base
microsoft/dotnet:2.2-sdk AS build

Windows:
microsoft/dotnet:2.2-aspnetcore-runtime-nanoserver-1803
microsoft/dotnet:2.2-sdk-nanoserver-1803

It is docker-compose.dcproj file where you can set up the OS you want to target:

<DockerTargetOS>Linux</DockerTargetOS>

To switch docker daemon to the same OS you can use Docker tray icon or Docker Settings window (accessible from the same menu):