According to the official documentation a recommended way to use npgsql 4.1
is via NuGet. Their provided MSI installer is somehow weak. The only way
we could make it visible to our Designer was installing npgsql 4.0 and then
upgrade to 4.1.  Then follow these additional steps to get it working.

npgsql 4.1 is available for .NET Framework and .NET Core. And the framework
version now depends on some .NET Core assemblies. The MSI package does not
provide them. At least they are not visible to our Designer when it is using
the npgsql connector.

You need to copy the missing assemblies to the Designer folder C:\Program Files\Windward Studios\Windward (the folder
where AutoTag*.dll files reside) manually.

Windward does not and can not include those assemblies with the Designer
distribution. As those are solely npgsql dependencies.

Below is a list of files you need to copy. An easy way to get all the files
would be to create a simple console application in Visual Studio. Add
a dependency to npgsql 4.1 to the application via NuGet. And build
the application. It's output folder will contain all files needed.

The file list.
Note: some files are not strictly required. For example Npgsql.dll
which is provided by the MSI installer. But it's up to the npgsql maintainers.

Microsoft.Bcl.AsyncInterfaces.dll

Microsoft.Win32.Primitives.dll

netstandard.dll

Npgsql.dll

System.AppContext.dll

System.Buffers.dll

System.Collections.Concurrent.dll

System.Collections.dll

System.Collections.NonGeneric.dll

System.Collections.Specialized.dll

System.ComponentModel.dll

System.ComponentModel.EventBasedAsync.dll

System.ComponentModel.Primitives.dll

System.ComponentModel.TypeConverter.dll

System.Console.dll

System.Data.Common.dll

System.Diagnostics.Contracts.dll

System.Diagnostics.Debug.dll

System.Diagnostics.FileVersionInfo.dll

System.Diagnostics.Process.dll

System.Diagnostics.StackTrace.dll

System.Diagnostics.TextWriterTraceListener.dll

System.Diagnostics.Tools.dll

System.Diagnostics.TraceSource.dll

System.Diagnostics.Tracing.dll

System.Drawing.Primitives.dll

System.Dynamic.Runtime.dll

System.Globalization.Calendars.dll

System.Globalization.dll

System.Globalization.Extensions.dll

System.IO.Compression.dll

System.IO.Compression.ZipFile.dll

System.IO.dll

System.IO.FileSystem.dll

System.IO.FileSystem.DriveInfo.dll

System.IO.FileSystem.Primitives.dll

System.IO.FileSystem.Watcher.dll

System.IO.IsolatedStorage.dll

System.IO.MemoryMappedFiles.dll

System.IO.Pipes.dll

System.IO.UnmanagedMemoryStream.dll

System.Linq.dll

System.Linq.Expressions.dll

System.Linq.Parallel.dll

System.Linq.Queryable.dll

System.Memory.dll

System.Net.Http.dll

System.Net.NameResolution.dll

System.Net.NetworkInformation.dll

System.Net.Ping.dll

System.Net.Primitives.dll

System.Net.Requests.dll

System.Net.Security.dll

System.Net.Sockets.dll

System.Net.WebHeaderCollection.dll

System.Net.WebSockets.Client.dll

System.Net.WebSockets.dll

System.Numerics.Vectors.dll

System.ObjectModel.dll

System.Reflection.dll

System.Reflection.Extensions.dll

System.Reflection.Primitives.dll

System.Resources.Reader.dll

System.Resources.ResourceManager.dll

System.Resources.Writer.dll

System.Runtime.CompilerServices.Unsafe.dll

System.Runtime.CompilerServices.VisualC.dll

System.Runtime.dll

System.Runtime.Extensions.dll

System.Runtime.Handles.dll

System.Runtime.InteropServices.dll

System.Runtime.InteropServices.RuntimeInformation.dll

System.Runtime.Numerics.dll

System.Runtime.Serialization.Formatters.dll

System.Runtime.Serialization.Json.dll

System.Runtime.Serialization.Primitives.dll

System.Runtime.Serialization.Xml.dll

System.Security.Claims.dll

System.Security.Cryptography.Algorithms.dll

System.Security.Cryptography.Csp.dll

System.Security.Cryptography.Encoding.dll

System.Security.Cryptography.Primitives.dll

System.Security.Cryptography.X509Certificates.dll

System.Security.Principal.dll

System.Security.SecureString.dll

System.Text.Encoding.dll

System.Text.Encoding.Extensions.dll

System.Text.Encodings.Web.dll

System.Text.Json.dll

System.Text.RegularExpressions.dll

System.Threading.dll

System.Threading.Overlapped.dll

System.Threading.Tasks.dll

System.Threading.Tasks.Extensions.dll

System.Threading.Tasks.Parallel.dll

System.Threading.Thread.dll

System.Threading.ThreadPool.dll

System.Threading.Timer.dll

System.ValueTuple.dll

System.Xml.ReaderWriter.dll

System.Xml.XDocument.dll

System.Xml.XmlDocument.dll

System.Xml.XmlSerializer.dll

System.Xml.XPath.dll

System.Xml.XPath.XDocument.dll