对于 ASP.NET Core 1.0 及更高版本

/// <summary>
/// <see cref="IUrlHelper"/> extension methods.
/// </summary>
public static class UrlHelperExtensions
{
    /// <summary>
    /// Generates a fully qualified URL to an action method by using the specified action name, controller name and
    /// route values.
    /// </summary>
    /// <param name="url">The URL helper.</param>
    /// <param name="actionName">The name of the action method.</param>
    /// <param name="controllerName">The name of the controller.</param>
    /// <param name="routeValues">The route values.</param>
    /// <returns>The absolute URL.</returns>
    public static string AbsoluteAction(
        this IUrlHelper url,
        string actionName,
        string controllerName,
        object routeValues = null)
    {
        return url.Action(actionName, controllerName, routeValues, url.ActionContext.HttpContext.Request.Scheme);
    }

    /// <summary>
    /// Generates a fully qualified URL to the specified content by using the specified content path. Converts a
    /// virtual (relative) path to an application absolute path.
    /// </summary>
    /// <param name="url">The URL helper.</param>
    /// <param name="contentPath">The content path.</param>
    /// <returns>The absolute URL.</returns>
    public static string AbsoluteContent(
        this IUrlHelper url,
        string contentPath)
    {
        HttpRequest request = url.ActionContext.HttpContext.Request;
        return new Uri(new Uri(request.Scheme + "://" + request.Host.Value), url.Content(contentPath)).ToString();
    }

    /// <summary>
    /// Generates a fully qualified URL to the specified route by using the route name and route values.
    /// </summary>
    /// <param name="url">The URL helper.</param>
    /// <param name="routeName">Name of the route.</param>
    /// <param name="routeValues">The route values.</param>
    /// <returns>The absolute URL.</returns>
    public static string AbsoluteRouteUrl(
        this IUrlHelper url,
        string routeName,
        object routeValues = null)
    {
        return url.RouteUrl(routeName, routeValues, url.ActionContext.HttpContext.Request.Scheme);
    }
}

额外提示

您不能直接在 DI 容器中注册 IUrlHelper.解析IUrlHelper 的实例需要您使用IUrlHelperFactory 和IActionContextAccessor.但是，您可以通过快捷方式执行以下操作:

Bonus Tip

You can't directly register an IUrlHelper in the DI container. Resolving an instance of IUrlHelper requires you to use the IUrlHelperFactory and IActionContextAccessor. However, you can do the following as a shortcut:

services
    .AddSingleton<IActionContextAccessor, ActionContextAccessor>()
    .AddScoped<IUrlHelper>(x => x
        .GetRequiredService<IUrlHelperFactory>()
        .GetUrlHelper(x.GetRequiredService<IActionContextAccessor>().ActionContext));

ASP.NET Core 待办事项

更新:这不会使 ASP.NET Core 5

ASP.NET Core Backlog

UPDATE: This won't make ASP.NET Core 5

有迹象表明，您将能够使用 LinkGenerator 创建绝对 URL，而无需提供 HttpContext(这是 LinkGenerator 的最大缺点 以及为什么 IUrlHelper 虽然使用下面的解决方案设置起来更复杂但更容易使用)请参阅 使用 LinkGenerator 轻松配置绝对 URL 的主机/方案".

There are indications that you will be able to use LinkGenerator to create absolute URLs without the need to provide a HttpContext (This was the biggest downside of LinkGenerator and why IUrlHelper although more complex to setup using the solution below was easier to use) See "Make it easy to configure a host/scheme for absolute URLs with LinkGenerator".