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N. Taylor Mullen
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Add extensions for TagHelperOutput to copy from TagBuilder.
- Added tests to validate functionality of all TagHelperOutputExtension methods. #1319
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‎src/Microsoft.AspNet.Mvc.TagHelpers/TagHelperOutputExtensions.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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/// Utility related extensions for <see cref="TagHelperOutput"/>.
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/// </summary>
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public static class TagHelperOutputExtensions
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{
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/// <summary>
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/// Merges the given <paramref name="tagBuilder"/> into the <paramref name="tagHelperOutput"/>.
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/// </summary>
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/// <param name="tagHelperOutput">The <see cref="TagHelperOutput"/>.</param>
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/// <param name="tagBuilder">The <see cref="TagBuilder"/> to merge.</param>
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public static void Merge(this TagHelperOutput tagHelperOutput, TagBuilder tagBuilder)
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{
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tagHelperOutput.TagName = tagBuilder.TagName;
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tagHelperOutput.Content += tagBuilder.InnerHtml;
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MergeAttributes(tagHelperOutput, tagBuilder);
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}
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/// <summary>
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/// Merges the given <see cref="tagBuilder"/>'s <see cref="TagBuilder.Attributes"/> into the
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/// <paramref name="tagHelperOutput"/>.
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/// </summary>
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/// <param name="tagHelperOutput">The <see cref="TagHelperOutput"/>.</param>
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/// <param name="tagBuilder">The <see cref="TagBuilder"/> to merge attributes from.</param>
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public static void MergeAttributes(this TagHelperOutput tagHelperOutput, TagBuilder tagBuilder)
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{
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foreach (var attribute in tagBuilder.Attributes)
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{
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if (!tagHelperOutput.Attributes.ContainsKey(attribute.Key))
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{
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tagHelperOutput.Attributes.Add(attribute.Key, attribute.Value);
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}
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else if (attribute.Key.Equals("class", StringComparison.Ordinal))
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{
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tagHelperOutput.Attributes["class"] += " " + attribute.Value;
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}
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}
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}
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/// <summary>
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/// Returns and removes all attributes from <paramref name="tagHelperOutput"/>'s
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/// <see cref="TagHelperOutput.Attributes"/> that have the given <paramref name="prefix"/>.
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/// </summary>
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/// <param name="tagHelperOutput">The <see cref="TagHelperOutput"/>.</param>
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/// <param name="prefix">The prefix to </param>
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/// <returns><see cref="KeyValuePair{string, string}"/>s whos <see cref="KeyValuePair{string, string}.Key"/>
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/// starts with the given <paramref name="prefix"/>.</returns>
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public static IEnumerable<KeyValuePair<string, string>> PullPrefixedAttributes(
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this TagHelperOutput tagHelperOutput, string prefix)
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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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var htmlAttributes = tagHelperOutput.Attributes;
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// We're only interested in HTML attributes that have the desired prefix.
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var prefixedAttributes = htmlAttributes.Where(attribute =>
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attribute.Key.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)).ToArray();
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// Since we're "pulling" the prefixed attribute values, we need to remove them.
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foreach (var attribute in prefixedAttributes)
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{
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htmlAttributes.Remove(attribute.Key);
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}
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return prefixedAttributes;
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}
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/// <summary>
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/// Restores a user provided bound attribute to the given <paramref name="tagHelperOutput"/>.
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/// </summary>
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/// <param name="tagHelperOutput">The <see cref="TagHelperOutput"/>.</param>
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/// <param name="boundAttributeName">The name of the bound attribute.</param>
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/// <param name="context">The <see cref="TagHelperContext"/>.</param>
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public static void RestoreBoundHtmlAttribute(this TagHelperOutput tagHelperOutput,
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string boundAttributeName,
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TagHelperContext context)
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{
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// We look for the original attribute so we can restore the exact attribute name the user typed.
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var entry = context.AllAttributes.Single(attribute =>
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attribute.Key.Equals(boundAttributeName, StringComparison.OrdinalIgnoreCase));
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var originalAttribute = new KeyValuePair<string, string>(entry.Key, entry.Value.ToString());
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tagHelperOutput.Attributes.Add(originalAttribute);
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}
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}
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}

‎test/Microsoft.AspNet.Mvc.TagHelpers.Test/TagHelperOutputExtensionsTest.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.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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using Xunit;
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namespace Microsoft.AspNet.Mvc.TagHelpers
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{
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public class TagHelperOutputExtensionsTest
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{
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[Theory]
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[InlineData("hello", "world")]
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[InlineData("HeLlO", "wOrLd")]
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public void RestoreBoundHtmlAttribute_RestoresOriginalAttributes(string attributeName, string attributeValue)
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>(),
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content: string.Empty);
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var tagHelperContext = new TagHelperContext(
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new Dictionary<string, object>()
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{
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{ attributeName, attributeValue }
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});
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var expectedAttribute = new KeyValuePair<string, string>(attributeName, attributeValue);
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// Act
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tagHelperOutput.RestoreBoundHtmlAttribute("hello", tagHelperContext);
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// Assert
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var attribute = Assert.Single(tagHelperOutput.Attributes);
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Assert.Equal(expectedAttribute, attribute);
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}
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[Fact]
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public void PullPrefixedAttributes_OnlyRemovesPrefixed_TagHelperOutputAttributeValues()
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>()
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{
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{ "route-Hello", "World" },
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{ "Route-I", "Am" }
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},
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content: string.Empty);
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var expectedAttribute = new KeyValuePair<string, string>("type", "btn");
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tagHelperOutput.Attributes.Add(expectedAttribute);
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// Act
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var pulledAttributes = tagHelperOutput.PullPrefixedAttributes("route-");
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// Assert
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var attribute = Assert.Single(tagHelperOutput.Attributes);
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Assert.Equal(expectedAttribute, attribute);
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attribute = Assert.Single(pulledAttributes, kvp => kvp.Key.Equals("route-Hello"));
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Assert.Equal(attribute.Value, "World");
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attribute = Assert.Single(pulledAttributes, kvp => kvp.Key.Equals("Route-I"));
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Assert.Equal(attribute.Value, "Am");
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}
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[Fact]
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public void PullPrefixedAttributes_ReturnsEmpty_AttributeListIfNoAttributesPrefixed()
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>()
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{
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{ "routeHello", "World" },
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{ "Routee-I", "Am" }
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},
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content: string.Empty);
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// Act
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var pulledAttributes = tagHelperOutput.PullPrefixedAttributes("route-");
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// Assert
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Assert.Empty(pulledAttributes);
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var attribute = Assert.Single(tagHelperOutput.Attributes, kvp => kvp.Key.Equals("routeHello"));
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Assert.Equal(attribute.Value, "World");
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attribute = Assert.Single(tagHelperOutput.Attributes, kvp => kvp.Key.Equals("Routee-I"));
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Assert.Equal(attribute.Value, "Am");
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}
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[Fact]
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public void MergeAttributes_DoesNotReplace_TagHelperOutputAttributeValues()
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>(),
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content: string.Empty);
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var expectedAttribute = new KeyValuePair<string, string>("type", "btn");
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tagHelperOutput.Attributes.Add(expectedAttribute);
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var tagBuilder = new TagBuilder("p");
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tagBuilder.Attributes.Add("type", "hello");
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// Act
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tagHelperOutput.MergeAttributes(tagBuilder);
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// Assert
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var attribute = Assert.Single(tagHelperOutput.Attributes);
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Assert.Equal(expectedAttribute, attribute);
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}
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[Fact]
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public void MergeAttributes_AppendsClass_TagHelperOutputAttributeValues()
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>(),
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content: string.Empty);
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tagHelperOutput.Attributes.Add("class", "Hello");
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var tagBuilder = new TagBuilder("p");
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tagBuilder.Attributes.Add("class", "btn");
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var expectedAttribute = new KeyValuePair<string, string>("class", "Hello btn");
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// Act
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tagHelperOutput.MergeAttributes(tagBuilder);
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// Assert
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var attribute = Assert.Single(tagHelperOutput.Attributes);
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Assert.Equal(expectedAttribute, attribute);
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}
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[Fact]
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public void MergeAttributes_DoesNotEncode_TagHelperOutputAttributeValues()
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>(),
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content: string.Empty);
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var tagBuilder = new TagBuilder("p");
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var expectedAttribute = new KeyValuePair<string, string>("visible", "val < 3");
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tagBuilder.Attributes.Add(expectedAttribute);
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// Act
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tagHelperOutput.MergeAttributes(tagBuilder);
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// Assert
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var attribute = Assert.Single(tagHelperOutput.Attributes);
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Assert.Equal(expectedAttribute, attribute);
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}
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[Fact]
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public void MergeAttributes_CopiesMultiple_TagHelperOutputAttributeValues()
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>(),
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content: string.Empty);
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var tagBuilder = new TagBuilder("p");
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var expectedAttribute1 = new KeyValuePair<string, string>("class", "btn");
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var expectedAttribute2 = new KeyValuePair<string, string>("class2", "btn");
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tagBuilder.Attributes.Add(expectedAttribute1);
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tagBuilder.Attributes.Add(expectedAttribute2);
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// Act
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tagHelperOutput.MergeAttributes(tagBuilder);
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// Assert
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Assert.Equal(2, tagHelperOutput.Attributes.Count);
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var attribute = Assert.Single(tagHelperOutput.Attributes, kvp => kvp.Key.Equals("class"));
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Assert.Equal(expectedAttribute1.Value, attribute.Value);
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attribute = Assert.Single(tagHelperOutput.Attributes, kvp => kvp.Key.Equals("class2"));
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Assert.Equal(expectedAttribute2.Value, attribute.Value);
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}
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[Fact]
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public void MergeAttributes_Maintains_TagHelperOutputAttributeValues()
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>(),
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content: string.Empty);
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var expectedAttribute = new KeyValuePair<string, string>("class", "btn");
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tagHelperOutput.Attributes.Add(expectedAttribute);
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var tagBuilder = new TagBuilder("p");
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// Act
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tagHelperOutput.MergeAttributes(tagBuilder);
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// Assert
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var attribute = Assert.Single(tagHelperOutput.Attributes);
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Assert.Equal(expectedAttribute, attribute);
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}
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[Fact]
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public void MergeAttributes_Combines_TagHelperOutputAttributeValues()
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>(),
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content: string.Empty);
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var expectedOutputAttribute = new KeyValuePair<string, string>("class", "btn");
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tagHelperOutput.Attributes.Add(expectedOutputAttribute);
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var tagBuilder = new TagBuilder("p");
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var expectedBuilderAttribute = new KeyValuePair<string, string>("for", "hello");
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tagBuilder.Attributes.Add(expectedBuilderAttribute);
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// Act
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tagHelperOutput.MergeAttributes(tagBuilder);
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// Assert
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Assert.Equal(tagHelperOutput.Attributes.Count, 2);
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var attribute = Assert.Single(tagHelperOutput.Attributes, kvp => kvp.Key.Equals("class"));
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Assert.Equal(expectedOutputAttribute.Value, attribute.Value);
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attribute = Assert.Single(tagHelperOutput.Attributes, kvp => kvp.Key.Equals("for"));
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Assert.Equal(expectedBuilderAttribute.Value, attribute.Value);
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}
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[Fact]
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public void Merge_CombinesAllTagHelperOutputAndTagBuilderProperties()
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{
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// Arrange
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var tagHelperOutput = new TagHelperOutput(
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"p",
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attributes: new Dictionary<string, string>(),
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content: "Hello from tagHelperOutput");
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var expectedOutputAttribute = new KeyValuePair<string, string>("class", "btn");
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tagHelperOutput.Attributes.Add(expectedOutputAttribute);
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var tagBuilder = new TagBuilder("div");
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var expectedBuilderAttribute = new KeyValuePair<string, string>("for", "hello");
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tagBuilder.Attributes.Add(expectedBuilderAttribute);
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tagBuilder.InnerHtml = "Hello from tagBuilder.";
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// Act
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tagHelperOutput.Merge(tagBuilder);
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// Assert
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Assert.Equal("div", tagHelperOutput.TagName);
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Assert.Equal("Hello from tagHelperOutputHello from tagBuilder.", tagHelperOutput.Content);
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Assert.Equal(tagHelperOutput.Attributes.Count, 2);
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var attribute = Assert.Single(tagHelperOutput.Attributes, kvp => kvp.Key.Equals("class"));
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Assert.Equal(expectedOutputAttribute.Value, attribute.Value);
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attribute = Assert.Single(tagHelperOutput.Attributes, kvp => kvp.Key.Equals("for"));
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Assert.Equal(expectedBuilderAttribute.Value, attribute.Value);
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}
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}
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}

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