Microsoft Edge WebView2 - Error: The type or namespace name 'Web' does not exist in the namespace 'Microsoft'

I'm working on this official tutorial: Getting started with WebView2 in WPF (Preview).

1. Have installed Microsoft Edge (Chromium) Canary channel on my Windows 10 pro -ver 1903.
2. Have created a .NET Core 3.1 - WPF project on latest version VS2019 - ver16.6.3.
3. Have installed the Nuget package Microsoft.Web.WebView2 -Version 0.9.538.

But, per instructions in step 3 of the tutorial, when I add namespace xmlns:wv2="clr-namespace:Microsoft.Web.WebView2.Wpf;assembly=Microsoft.Web.WebView2.Wpf" in <Window/> tag of MainWindow.xaml, and build (F5) the app, I get the following error at line using Microsoft.Web.WebView2.Wpf; of the MainWindow.g.cs file:

Error:

Error CS0234 The type or namespace name 'Web' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?)

MainWindow.xaml:

<Window x:Class="WpfWebView2TEST.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:wv2="clr-namespace:Microsoft.Web.WebView2.Wpf;assembly=Microsoft.Web.WebView2.Wpf"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        
    </Grid>
</Window>

Question: What may be a cause of the error and how can it be resoled?