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N. Taylor Mullen
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Add Label TagHelper.
- Validated label TagHelper functionality. #1249
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‎src/Microsoft.AspNet.Mvc.TagHelpers/LabelTagHelper.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 Microsoft.AspNet.Mvc.Rendering;
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using Microsoft.AspNet.Razor.Runtime.TagHelpers;
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using Microsoft.AspNet.Razor.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;label&gt; elements with <c>for</c> attributes.
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/// </summary>
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[ContentBehavior(ContentBehavior.Modify)]
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public class LabelTagHelper : TagHelper
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{
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[Activate]
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protected internal ViewContext ViewContext { get; set; }
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[Activate]
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protected internal IHtmlGenerator Generator { get; set; }
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/// <summary>
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/// An expression to be evaluated against the current model.
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/// </summary>
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public ModelExpression For { get; set; }
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/// <inheritdoc />
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public override void Process(TagHelperContext context, TagHelperOutput output)
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{
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if (For != null)
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{
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var tagBuilder = Generator.GenerateLabel(ViewContext,
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For.Metadata,
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For.Name,
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labelText: null,
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htmlAttributes: null);
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if (tagBuilder != null)
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{
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output.MergeAttributes(tagBuilder);
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// We check for whitespace to detect scenarios such as:
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// <label for="Name">
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// </label>
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if (string.IsNullOrWhiteSpace(output.Content))
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{
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output.Content = tagBuilder.InnerHtml;
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}
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output.TagName = tagBuilder.TagName;
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}
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}
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}
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}
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}

‎test/Microsoft.AspNet.Mvc.TagHelpers.Test/LabelTagHelperTest.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.Threading.Tasks;
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using Microsoft.AspNet.Mvc.ModelBinding;
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using Microsoft.AspNet.Mvc.Razor;
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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 LabelTagHelperTest
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{
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// Model (List<Model> or Model instance), container type (Model or NestModel), model accessor,
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// property path, TagHelperOutput.Content values.
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public static TheoryData<object, Type, Func<object>, string, TagHelperOutputContent> TestDataSet
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{
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get
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{
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var modelWithNull = new Model
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{
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NestedModel = new NestedModel
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{
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Text = null,
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},
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Text = null,
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};
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var modelWithText = new Model
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{
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NestedModel = new NestedModel
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{
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Text = "inner text",
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},
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Text = "outer text",
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};
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var models = new List<Model>
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{
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modelWithNull,
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modelWithText,
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};
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return new TheoryData<object, Type, Func<object>, string, TagHelperOutputContent>
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{
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{ null, typeof(Model), () => null, "Text",
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new TagHelperOutputContent(Environment.NewLine, "Text") },
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{ modelWithNull, typeof(Model), () => modelWithNull.Text, "Text",
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new TagHelperOutputContent(Environment.NewLine, "Text") },
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{ modelWithText, typeof(Model), () => modelWithText.Text, "Text",
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new TagHelperOutputContent(Environment.NewLine, "Text") },
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{ modelWithText, typeof(Model), () => modelWithNull.Text, "Text",
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new TagHelperOutputContent("Hello World", "Hello World") },
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{ modelWithText, typeof(Model), () => modelWithText.Text, "Text",
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new TagHelperOutputContent("Hello World", "Hello World") },
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{ modelWithNull, typeof(NestedModel), () => modelWithNull.NestedModel.Text, "NestedModel.Text",
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new TagHelperOutputContent(Environment.NewLine, "Text") },
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{ modelWithText, typeof(NestedModel), () => modelWithText.NestedModel.Text, "NestedModel.Text",
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new TagHelperOutputContent(Environment.NewLine, "Text") },
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{ modelWithNull, typeof(NestedModel), () => modelWithNull.NestedModel.Text, "NestedModel.Text",
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new TagHelperOutputContent("Hello World", "Hello World") },
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{ modelWithText, typeof(NestedModel), () => modelWithText.NestedModel.Text, "NestedModel.Text",
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new TagHelperOutputContent("Hello World", "Hello World") },
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// Note: Tests cases below here will not work in practice due to current limitations on indexing
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// into ModelExpressions. Will be fixed in https://github.com/aspnet/Mvc/issues/1345.
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{ models, typeof(Model), () => models[0].Text, "[0].Text",
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new TagHelperOutputContent(Environment.NewLine, "Text") },
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{ models, typeof(Model), () => models[1].Text, "[1].Text",
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new TagHelperOutputContent(Environment.NewLine, "Text") },
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{ models, typeof(Model), () => models[0].Text, "[0].Text",
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new TagHelperOutputContent("Hello World", "Hello World") },
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{ models, typeof(Model), () => models[1].Text, "[1].Text",
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new TagHelperOutputContent("Hello World", "Hello World") },
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{ models, typeof(NestedModel), () => models[0].NestedModel.Text, "[0].NestedModel.Text",
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new TagHelperOutputContent(Environment.NewLine, "Text") },
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{ models, typeof(NestedModel), () => models[1].NestedModel.Text, "[1].NestedModel.Text",
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new TagHelperOutputContent(Environment.NewLine, "Text") },
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{ models, typeof(NestedModel), () => models[0].NestedModel.Text, "[0].NestedModel.Text",
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new TagHelperOutputContent("Hello World", "Hello World") },
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{ models, typeof(NestedModel), () => models[1].NestedModel.Text, "[1].NestedModel.Text",
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new TagHelperOutputContent("Hello World", "Hello World") },
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};
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}
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}
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[Theory]
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[MemberData(nameof(TestDataSet))]
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public async Task ProcessAsync_GeneratesExpectedOutput(
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object model,
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Type containerType,
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Func<object> modelAccessor,
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string propertyPath,
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TagHelperOutputContent tagHelperOutputContent)
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{
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// Arrange
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var expectedAttributes = new Dictionary<string, string>
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{
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{ "class", "form-control" },
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{ "for", propertyPath }
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};
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var metadataProvider = new DataAnnotationsModelMetadataProvider();
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// Property name is either nameof(Model.Text) or nameof(NestedModel.Text).
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var metadata = metadataProvider.GetMetadataForProperty(modelAccessor, containerType, propertyName: "Text");
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var modelExpression = new ModelExpression(propertyPath, metadata);
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var tagHelper = new LabelTagHelper
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{
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For = modelExpression,
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};
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var tagHelperContext = new TagHelperContext(allAttributes: new Dictionary<string, object>());
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var htmlAttributes = new Dictionary<string, string>
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{
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{ "class", "form-control" },
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};
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var output = new TagHelperOutput("A random tag name", htmlAttributes, tagHelperOutputContent.OriginalContent);
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var expectedTagName = "label";
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var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
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var viewContext = TestableHtmlGenerator.GetViewContext(model, htmlGenerator, metadataProvider);
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tagHelper.ViewContext = viewContext;
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tagHelper.Generator = htmlGenerator;
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// Act
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await tagHelper.ProcessAsync(tagHelperContext, output);
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// Assert
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Assert.Equal(expectedAttributes, output.Attributes);
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Assert.Equal(tagHelperOutputContent.ExpectedContent, output.Content);
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Assert.False(output.SelfClosing);
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Assert.Equal(expectedTagName, output.TagName);
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}
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[Fact]
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public async Task TagHelper_LeavesOutputUnchanged_IfForNotBound2()
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{
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// Arrange
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var expectedAttributes = new Dictionary<string, string>
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{
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{ "class", "form-control" },
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};
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var expectedContent = "original content";
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var expectedTagName = "original tag name";
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var metadataProvider = new DataAnnotationsModelMetadataProvider();
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var metadata = metadataProvider.GetMetadataForProperty(
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modelAccessor: () => null,
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containerType: typeof(Model),
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propertyName: nameof(Model.Text));
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var modelExpression = new ModelExpression(nameof(Model.Text), metadata);
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var tagHelper = new LabelTagHelper();
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var tagHelperContext = new TagHelperContext(allAttributes: new Dictionary<string, object>());
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var output = new TagHelperOutput(expectedTagName, expectedAttributes, expectedContent);
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var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
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Model model = null;
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var viewContext = TestableHtmlGenerator.GetViewContext(model, htmlGenerator, metadataProvider);
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var activator = new DefaultTagHelperActivator();
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activator.Activate(tagHelper, viewContext);
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// Act
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await tagHelper.ProcessAsync(tagHelperContext, output);
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// Assert
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Assert.Equal(expectedAttributes, output.Attributes);
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Assert.Equal(expectedContent, output.Content);
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Assert.Equal(expectedTagName, output.TagName);
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}
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public class TagHelperOutputContent
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{
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public TagHelperOutputContent(string outputContent, string expectedContent)
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{
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OriginalContent = outputContent;
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ExpectedContent = expectedContent;
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}
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public string OriginalContent { get; set; }
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public string ExpectedContent { get; set; }
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}
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private class Model
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{
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public string Text { get; set; }
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public NestedModel NestedModel { get; set; }
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}
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private class NestedModel
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{
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public string Text { get; set; }
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}
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}
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}

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