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NTaylorMullen
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Add AnchorTagHelper.
- Added a TagHelper that targets the <a> tag and allows users to do the equivalent of Html.ActionLink or Html.RouteLink. #1247
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‎src/Microsoft.AspNet.Mvc.TagHelpers/AnchorTagHelper.cs‎

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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
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// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using Microsoft.AspNet.Mvc.Rendering;
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using Microsoft.AspNet.Razor.Runtime.TagHelpers;
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namespace Microsoft.AspNet.Mvc.TagHelpers
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{
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/// <summary>
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/// <see cref="ITagHelper"/> implementation targeting &lt;a&gt; elements.
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/// </summary>
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[TagName("a")]
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public class AnchorTagHelper : TagHelper
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{
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private const string RouteAttributePrefix = "route-";
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private const string Href = "href";
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[Activate]
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private IHtmlGenerator Generator { get; set; }
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/// <summary>
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/// The name of the action method.
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/// </summary>
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/// <remarks>Cannot be provided if <see cref="Route"/> is specified.</remarks>
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public string Action { get; set; }
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/// <summary>
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/// The name of the controller.
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/// </summary>
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/// <remarks>Cannot be provided if <see cref="Route"/> is specified.</remarks>
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public string Controller { get; set; }
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/// <summary>
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/// The protocol for the URL, such as &quot;http&quot; or &quot;https&quot;.
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/// </summary>
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public string Protocol { get; set; }
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/// <summary>
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/// The host name for the URL.
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/// </summary>
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public string Host { get; set; }
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/// <summary>
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/// The URL fragment name (the anchor name).
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/// </summary>
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public string Fragment { get; set; }
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/// <summary>
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/// Name of the route.
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/// </summary>
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/// <remarks>Cannot be provided if <see cref="Action"/> or <see cref="Controller"/> is specified.</remarks>
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public string Route { get; set; }
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/// <inheritdoc />
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/// <remarks>Does nothing if user provides a "href" attribute. Cannot specify a "href" attribute AND
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/// <see cref="Action"/>, <see cref="Controller"/> or <see cref="Route"/>.</remarks>
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public override void Process(TagHelperContext context, TagHelperOutput output)
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{
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// If there's an "href" on the tag it means it's being used as a normal anchor.
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if (output.Attributes.ContainsKey(Href))
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{
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if (Action != null || Controller != null || Route != null)
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{
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// User specified an href AND a Action, Controller or Route; can't determine the href attribute.
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throw new InvalidOperationException(
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Resources.FormatAnchorTagHelper_CannotDetermineHrefOneSpecified(
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nameof(AnchorTagHelper),
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nameof(Action),
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nameof(Controller),
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nameof(Route),
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Href));
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}
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// User is using the AnchorTagHelper as normal anchor tag, restore any provided attributes.
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RestoreBoundHtmlAttributes(context, output);
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}
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else
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{
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TagBuilder tagBuilder;
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var prefixedValues = output.PullPrefixedAttributes(RouteAttributePrefix);
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Dictionary<string, object> routeValues = null;
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if (prefixedValues.Any())
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{
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// Generator.GenerateActionLink || GenerateRouteLink does not accept a Dictionary<string, string> for
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// route values.
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routeValues = prefixedValues.ToDictionary(
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attribute => attribute.Key.Substring(RouteAttributePrefix.Length),
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attribute => (object)attribute.Value);
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}
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if (Route == null)
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{
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tagBuilder = Generator.GenerateActionLink(linkText: string.Empty,
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actionName: Action,
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controllerName: Controller,
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protocol: Protocol,
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hostname: Host,
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fragment: Fragment,
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routeValues: routeValues,
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htmlAttributes: null);
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}
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else if (Action != null || Controller != null)
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{
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// Route and Action or Controller were specified. Can't determine the href attribute.
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throw new InvalidOperationException(
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Resources.FormatAnchorTagHelper_CannotDetermineHrefRouteActionOrControllerSpecified(
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nameof(AnchorTagHelper),
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nameof(Route),
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nameof(Action),
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nameof(Controller),
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Href));
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}
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else
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{
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tagBuilder = Generator.GenerateRouteLink(linkText: string.Empty,
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routeName: Route,
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protocol: Protocol,
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hostName: Host,
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fragment: Fragment,
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routeValues: routeValues,
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htmlAttributes: null);
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}
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output.MergeAttributes(tagBuilder);
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}
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}
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// Restores bound HTML attributes when we detect that a user is using the AnchorTagHelper as a normal <a> tag.
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private void RestoreBoundHtmlAttributes(TagHelperContext context, TagHelperOutput output)
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{
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if (Action != null)
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{
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output.RestoreBoundHtmlAttribute(nameof(Action), context);
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}
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if (Controller != null)
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{
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output.RestoreBoundHtmlAttribute(nameof(Controller), context);
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}
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if (Protocol != null)
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{
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output.RestoreBoundHtmlAttribute(nameof(Protocol), context);
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}
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if (Host != null)
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{
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output.RestoreBoundHtmlAttribute(nameof(Host), context);
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}
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if (Fragment != null)
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{
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output.RestoreBoundHtmlAttribute(nameof(Fragment), context);
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}
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if (Route != null)
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{
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output.RestoreBoundHtmlAttribute(nameof(Route), context);
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}
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}
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}
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}

‎src/Microsoft.AspNet.Mvc.TagHelpers/Properties/Resources.Designer.cs‎

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‎src/Microsoft.AspNet.Mvc.TagHelpers/Resources.resx‎

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<resheader name="writer">
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<value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
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</resheader>
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<data name="AnchorTagHelper_CannotDetermineHrefOneSpecified" xml:space="preserve">
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<value>Cannot determine an {4} for {0}. A {0} with a specified {4] must not have a {1}, {2} or {3} attribute.</value>
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</data>
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<data name="AnchorTagHelper_CannotDetermineHrefRouteActionOrControllerSpecified" xml:space="preserve">
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<value>Cannot determine an {4} for {0}. A {0} with a specified {1} must not have a {2} or {3} attribute.</value>
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</data>
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<data name="FormTagHelper_CannotDetermineAction" xml:space="preserve">
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<value>Cannot determine an {1} for {0}. A {0} with a URL-based {1} must not have attributes starting with {3} or a {2} attribute.</value>
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</data>

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