[Fixes #2788] Added a sample taghelper that handles IE conditional comments

samples/TagHelperSample.Web/Controllers/TagHelperController.cs

@@ -0,0 +1,15 @@
+// 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 Microsoft.AspNet.Mvc;
+
+namespace TagHelperSample.Web.Controllers
+{
+    public class TagHelperController : Controller
+    {
+        public IActionResult ConditionalComment()
+        {
+            return View();
+        }
+    }
+}

samples/TagHelperSample.Web/TagHelpers/CommentMode.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.
+
+namespace TagHelperSample.Web
+{
+    public enum CommentMode
+    {
+        DownlevelHidden = 0,
+
+        DownlevelRevealed = 1
+    }
+}

samples/TagHelperSample.Web/TagHelpers/ConditionalCommentTagHelper.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 Microsoft.AspNet.Razor.Runtime.TagHelpers;
+
+namespace TagHelperSample.Web
+{
+    [TargetElement("iecondition")]
+    public class ConditionalCommentTagHelper : TagHelper
+    {
+        public CommentMode Mode { get; set; }
+
+        public string Condition { get; set; }
+
+        public override void Process(TagHelperContext context, TagHelperOutput output)
+        {
+            output.TagName = null;
+
+            var modeModifier = string.Empty;
+
+            if (Mode == CommentMode.DownlevelHidden)
+            {
+                modeModifier = "--";
+            }
+
+            output.PreContent.Append("<!");
+            output.PreContent.Append(modeModifier);
+            output.PreContent.Append("[if ");
+            output.PreContent.Append(Condition);
+            output.PreContent.Append("]>");
+
+            output.PostContent.Append("<![endif]");
+            output.PostContent.Append(modeModifier);
+            output.PostContent.Append(">");
+        }
+    }
+}

samples/TagHelperSample.Web/Views/TagHelper/ConditionalComment.cshtml

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+@using TagHelperSample.Web
+@addTagHelper "*, TagHelperSample.Web"
+
+<iecondition mode="@CommentMode.DownlevelRevealed" condition="gt IE 7">
+    <p>Content visible to all browsers newer than Internet Explorer 7.</p>
+</iecondition>
+<iecondition mode="@CommentMode.DownlevelHidden" condition="IE 7">
+    <p>Content visible only to Internet Explorer 7 users.</p>
+</iecondition>