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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. - Added tests to validate AnchorTagHelper functionality. #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>Must be <c>null</c> if <see cref="Route"/> is non-<c>null</c>.</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>Must be <c>null</c> if <see cref="Route"/> is non-<c>null</c>.</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.
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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.
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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>
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/// Must be <c>null</c> if <see cref="Action"/> or <see cref="Controller"/> is non-<c>null</c>.
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/// </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 an "href" attribute. Throws an
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/// <see cref="InvalidOperationException"/> if "href" attribute is provided and <see cref="Action"/>,
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/// <see cref="Controller"/>, or <see cref="Route"/> are non-<c>null</c>.</remarks>
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public override void Process(TagHelperContext context, TagHelperOutput output)
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{
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var routePrefixedAttributes = output.FindPrefixedAttributes(RouteAttributePrefix);
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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 ||
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Controller != null ||
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Route != null ||
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Protocol != null ||
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Host != null ||
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Fragment != null ||
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routePrefixedAttributes.Any())
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{
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// User specified an href and one of the bound attributes; can't determine the href attribute.
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throw new InvalidOperationException(
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Resources.FormatAnchorTagHelper_CannotOverrideSpecifiedHref(
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"<a>",
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nameof(Action).ToLowerInvariant(),
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nameof(Controller).ToLowerInvariant(),
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nameof(Route).ToLowerInvariant(),
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nameof(Protocol).ToLowerInvariant(),
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nameof(Host).ToLowerInvariant(),
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nameof(Fragment).ToLowerInvariant(),
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RouteAttributePrefix,
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Href));
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}
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}
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else
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{
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TagBuilder tagBuilder;
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var routeValues = GetRouteValues(output, routePrefixedAttributes);
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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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"<a>",
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nameof(Route).ToLowerInvariant(),
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nameof(Action).ToLowerInvariant(),
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nameof(Controller).ToLowerInvariant(),
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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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if (tagBuilder != null)
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{
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output.MergeAttributes(tagBuilder);
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}
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}
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}
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// TODO: We will not need this method once https://github.com/aspnet/Razor/issues/89 is completed.
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private static Dictionary<string, object> GetRouteValues(
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TagHelperOutput output, IEnumerable<KeyValuePair<string, string>> routePrefixedAttributes)
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{
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Dictionary<string, object> routeValues = null;
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if (routePrefixedAttributes.Any())
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{
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// Prefixed values should be treated as bound attributes, remove them from the output.
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output.RemoveRange(routePrefixedAttributes);
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// Generator.GenerateForm does not accept a Dictionary<string, string> for route values.
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routeValues = routePrefixedAttributes.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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return routeValues;
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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_CannotDetermineHrefRouteActionOrControllerSpecified" xml:space="preserve">
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<value>Cannot determine an {4} for {0}. An {0} with a specified {1} must not have an {2} or {3} attribute.</value>
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</data>
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<data name="AnchorTagHelper_CannotOverrideSpecifiedHref" xml:space="preserve">
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<value>Cannot determine an {8} for {0}. An {0} with a specified {8} must not have attributes starting with {7} or an {1}, {2}, {3}, {4}, {5} or {6} 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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