The interop files SQLite.Interop.dll in the x86/x64 subfolders not present during Visual Studio's post-build event in VS 2019. They are placed there (by the build target in System.Data.SQLite.Core.targets?) after the post-build event is finished.

A similar problem was reported and resolved in ticket

The file System.Data.SQLite.Core.targets contains a list of Visual Studio versions (line 131 ff) where VS 2019 ("16.0") is missing, but I don't know whether this is related.

Build environment
-----------------

* Win 10 German
* Visual Studio 2019 (16.2.2)
* .Net 4.7.2

Example to reproduce
--------------------

SQLitePostBuild.csproj (contains post-build event that checks for the interop file in debug subfolder, build forced to fail if not found):
###
  <Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
      <OutputType>Exe</OutputType>
      <TargetFramework>net472</TargetFramework>
    </PropertyGroup>

    <ItemGroup>
      <PackageReference Include="System.Data.SQLite" Version="1.0.111" />
    </ItemGroup>

    <Target Name="PostBuild" AfterTargets="PostBuildEvent">
      <Exec Command="REM Checks whether the interop file exists during Post-build event.&#xD;&#xA;REM Other files in the output folder (ex. SQLitePostBuild.exe) would be found.&#xD;&#xA;IF EXIST (&#xD;&#xA;  exit 0&#xD;&#xA;) ELSE (&#xD;&#xA;  exit 1&#xD;&#xA;)" />
    </Target>

  </Project>
###

Program.cs (just a minimal hello world):

###
  namespace SQLitePostBuild
  {
    class Program
    {
      static void Main() => System.Console.WriteLine("Hello SQLite!");
    }
  }
###