以下是一个使用ASP.NET OWIN和OAuth2.0的示例，包括刷新令牌。

首先，确保已经安装了以下NuGet包：

• Microsoft.Owin
• Microsoft.Owin.Host.SystemWeb
• Microsoft.Owin.Security
• Microsoft.Owin.Security.Cookies
• Microsoft.Owin.Security.OAuth

然后，在Startup.cs文件中，添加以下代码：

using Microsoft.Owin;
using Microsoft.Owin.Security;
using Microsoft.Owin.Security.Cookies;
using Microsoft.Owin.Security.OAuth;
using Owin;
using System;

[assembly: OwinStartup(typeof(YourNamespace.Startup))]

namespace YourNamespace
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
                LoginPath = new PathString("/Account/Login")
            });

            app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);

            app.UseOAuthAuthorizationServer(new OAuthAuthorizationServerOptions
            {
                TokenEndpointPath = new PathString("/Token"), // 设置Token的请求路径
                Provider = new YourAuthorizationProvider(), // 自定义的授权提供程序
                AccessTokenExpireTimeSpan = TimeSpan.FromMinutes(30), // 设置访问令牌的过期时间
                AllowInsecureHttp = true // 允许在非安全连接上使用令牌
            });

            app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());

            // 其他配置...
        }
    }
}

接下来，创建一个自定义的授权提供程序（YourAuthorizationProvider.cs），并实现OAuthAuthorizationServerProvider类：

using Microsoft.Owin.Security;
using Microsoft.Owin.Security.OAuth;
using System.Collections.Generic;
using System.Security.Claims;
using System.Threading.Tasks;

namespace YourNamespace
{
    public class YourAuthorizationProvider : OAuthAuthorizationServerProvider
    {
        public override Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context)
        {
            context.Validated();
            return Task.FromResult