Install libphonenumber-csharp
You can install it throught Visual Studio by right cliking on the project and choosing Manage Nuget pakcages...search phonenumber:
Or you can enter the following command in a Package Manager Console window, substituting the current version information as appropriate:
PM> Install-Package libphonenumber-csharp -Version 8.11.1
Or enter the following .NET command line in a PowerShell window. Be sure the current directory is the project directory:
dotnet add package libphonenumber-csharp --version 8.11.1