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TagHelperRunner.cs
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TagHelperRunner.cs
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// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Razor.TagHelpers;
namespace Microsoft.AspNetCore.Razor.Runtime.TagHelpers
{
/// <summary>
/// A class used to run <see cref="ITagHelper"/>s.
/// </summary>
public class TagHelperRunner
{
/// <summary>
/// Calls the <see cref="ITagHelperComponent.ProcessAsync"/> method on <see cref="ITagHelper"/>s.
/// </summary>
/// <param name="executionContext">Contains information associated with running <see cref="ITagHelper"/>s.
/// </param>
/// <returns>Resulting <see cref="TagHelperOutput"/> from processing all of the
/// <paramref name="executionContext"/>'s <see cref="ITagHelper"/>s.</returns>
public async Task RunAsync(TagHelperExecutionContext executionContext)
{
if (executionContext == null)
{
throw new ArgumentNullException(nameof(executionContext));
}
var tagHelperContext = executionContext.Context;
OrderTagHelpers(executionContext.TagHelpers);
for (var i = 0; i < executionContext.TagHelpers.Count; i++)
{
executionContext.TagHelpers[i].Init(tagHelperContext);
}
var tagHelperOutput = executionContext.Output;
for (var i = 0; i < executionContext.TagHelpers.Count; i++)
{
await executionContext.TagHelpers[i].ProcessAsync(tagHelperContext, tagHelperOutput);
}
}
private static void OrderTagHelpers(IList<ITagHelper> tagHelpers)
{
// Using bubble-sort here due to its simplicity. It'd be an extreme corner case to ever have more than 3 or
// 4 tag helpers simultaneously.
ITagHelper temp = null;
for (var i = 0; i < tagHelpers.Count; i++)
{
for (var j = i + 1; j < tagHelpers.Count; j++)
{
if (tagHelpers[j].Order < tagHelpers[i].Order)
{
temp = tagHelpers[i];
tagHelpers[i] = tagHelpers[j];
tagHelpers[j] = temp;
}
}
}
}
}
}