using Microsoft.Extensions.DependencyInjection; using ExcelAddIn.Services; using System.Text; public class MyAddIn : IExcelAddIn {     public static ServiceProvider ServiceProvider { get; private set; }     public void AutoOpen()     {            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);         IServiceCollection Services = new ServiceCollection();         Services.AddHttpClient()             .AddSingleton();         ServiceProvider = Services.BuildServiceProvider();     }     public void AutoClose()     {     } }