要实现ASP.NET Core绑定IdentityUser的外部登录，而不使用Razor Pages，可以按照以下步骤进行操作：

步骤1: 添加必要的NuGet包 首先，确保已安装了以下NuGet包：

• Microsoft.AspNetCore.Authentication
• Microsoft.AspNetCore.Identity.EntityFrameworkCore
• Microsoft.EntityFrameworkCore
• Microsoft.EntityFrameworkCore.SqlServer

步骤2: 配置Identity 在Startup.cs文件的ConfigureServices方法中，添加以下代码来配置Identity服务：

services.AddDbContext(options =>
    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

services.AddIdentity()
    .AddEntityFrameworkStores()
    .AddDefaultTokenProviders();

步骤3: 配置外部登录 在Startup.cs文件的ConfigureServices方法中，添加以下代码来配置外部登录服务：

services.AddAuthentication()
    .AddGoogle(options =>
    {
        options.ClientId = Configuration["Google:ClientId"];
        options.ClientSecret = Configuration["Google:ClientSecret"];
    })
    .AddFacebook(options =>
    {
        options.AppId = Configuration["Facebook:AppId"];
        options.AppSecret = Configuration["Facebook:AppSecret"];
    });

步骤4: 注册登录控制器 在Startup.cs文件的Configure方法中，添加以下代码来注册登录控制器：

app.UseAuthentication();

app.UseMvc(routes =>
{
    routes.MapRoute(
        name: "default",
        template: "{controller=Home}/{action=Index}/{id?}");
});

步骤5: 创建登录视图 创建一个名为Login.cshtml的视图文件，包含以下代码：

Login

    Login with Google
    Login with Facebook

步骤6: 创建登录控制器 创建一个名为AccountController.cs的控制器文件，包含以下代码：

public class AccountController : Controller
{
    private readonly SignInManager _signInManager;
    private readonly UserManager _userManager;

    public AccountController(SignInManager signInManager, UserManager userManager)
    {
        _signInManager = signInManager;
        _userManager = userManager;
    }

    public IActionResult ExternalLogin(string provider)
    {
        var redirectUrl = Url.Action(nameof(ExternalLoginCallback));
        var properties = _signInManager.ConfigureExternalAuthenticationProperties(provider, redirectUrl);
        return Challenge(properties, provider);
    }

    public async Task ExternalLoginCallback()
    {
        var info = await _signInManager.GetExternalLoginInfoAsync();
        if (info == null)
        {
            // 外部登录失败的处理逻辑
            return RedirectToAction(nameof(Login));
        }

        var result = await _signInManager.ExternalLoginSignInAsync(info.LoginProvider, info.ProviderKey, isPersistent: false);
        if (result.Succeeded)
        {
            // 外部登录成功的处理逻辑
            return RedirectToAction("Index", "Home");
        }

        // 外部登录成功，但未绑定到本地用户的处理逻辑
        var email = info.Principal.FindFirstValue(ClaimTypes.Email);
        var user = new IdentityUser
        {
            UserName = email,
            Email = email
        };
        var createResult = await _userManager.CreateAsync(user);
        if (createResult.Succeeded)
        {
            createResult = await _userManager.AddLoginAsync(user, info);
            if (createResult.Succeeded)
            {
                await _signInManager.ExternalLoginSignInAsync(info.LoginProvider, info.ProviderKey, isPersistent: false);
                return RedirectToAction("Index", "Home");
            }
        }

        // 创建用户或绑定失败的处理逻辑
        return RedirectToAction(nameof(Login));
    }
}

通过以上步骤，就可以实现ASP.NET Core绑定IdentityUser的外部登录，而不使用Razor Pages。请确保在appsettings.json文件中配置了正确的Google和Facebook API凭据。