Error the process cannot access the file because it is being used by another process while building project by CLI on .NET Core

Question

I got following error while running dotnet build command on my .NET Core project.

C:\Program Files\dotnet\sdk\2.1.2\Microsoft.Common.CurrentVersion.targets(4106,5
 ): warning MSB3026: Could not copy "obj\Debug\netcoreapp2.0\Blog-Yantra.dll" to
 "bin\Debug\netcoreapp2.0\Blog-Yantra.dll". Beginning retry 1 in 1000ms. The proc
 ess cannot access the file 'E:\learn\blog\Blog-Yantra\bin\Debug\netcoreapp2.0\Bl
 og-Yantra.dll' because it is being used by another process.  [E:\learn\blog\Blog
 -Yantra\Blog-Yantra.csproj]

And my csproj file looks like:

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

  <PropertyGroup>
    <TargetFramework>netcoreapp2.0</TargetFramework>
    <TypeScriptToolsVersion>2.3</TypeScriptToolsVersion>
  </PropertyGroup>

  <ItemGroup>
    <Folder Include="wwwroot\" />
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.3" />
    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="2.0.1" />
    <PackageReference Include="Microsoft.AspNetCore.StaticFiles" Version="2.0.1" />
  </ItemGroup>
  <ItemGroup>
    <DotNetCliToolReference Include="Microsoft.DotNet.Watcher.Tools" Version="2.0.0" />
  </ItemGroup>
</Project>

Answer 1

Most likely an open .Net core process running and blocking, if on windows, just kill it through the task manager.

Answer 2

The solution for me is to stop the IIS Express processes by right-clicking on the taskbar icon.

Or you can make a command line in "Pre-Build Event":

$(Solution)taskkill /FI "IMAGENAME eq iisexpress.exe" /F

Add this command in the "Properties" of your projet > "Build Events"

We don't have time to see if the command has been executed properly in "Ouput" view into "Build" section. Add this command line in "Pre-Build Event" to see the results:

cmd /c pause

You can remove this line after check...