services.Configure<RazorViewEngineOptions>(o => {
    o.ViewLocationFormats.Add("/{0}" + RazorViewEngine.ViewExtension);
    o.FileProviders.Clear();
    o.FileProviders.Add(new PhysicalFileProvider(AppContext.BaseDirectory));
});

<ItemGroup>
  <Content Include="Documents***.cshtml">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
  </Content>
</ItemGroup>

public async Task<string> RenderAsync<TModel>(string name, TModel model) {
    var actionContext = GetDefaultActionContext();
    var viewEngineResult = _viewEngine.GetView(null, name, true);

    if (!viewEngineResult.Success) {
        throw new InvalidOperationException($"View '{name}' cannot be found.");
    }

    var view = viewEngineResult.View;
    using (var output = new StringWriter()) {
        var viewContext = new ViewContext(actionContext, view,
            new ViewDataDictionary<TModel>(
                metadataProvider: new EmptyModelMetadataProvider(),
                modelState: new ModelStateDictionary()) {
                Model = model
            },
            new TempDataDictionary(
                actionContext.HttpContext,
                _tempDataProvider),
            output,
            new HtmlHelperOptions());

        await view.RenderAsync(viewContext);
        return output.ToString();
    }
}