Add Meta tag in View page using MVC-5

Question 1

I found a way that works for now.

This solution mostly use when multiple master page.

In the controllers / action assign whatever meta info you need for that view.

ViewBag.Title = "some title";
ViewBag.MetaDescription = "some description";

In the View or master page get whatever meta info you need for that view.

 @if(ViewBag.MetaDescription != null)
    {
        <meta name="description" content="@ViewBag.MetaDescription" />
    }

    @if(ViewBag.MetaKeywords != null)
    {
        <meta name="keywords" content="@ViewBag.MetaKeywords" />
    }

Question 2

It should work.

Here's my master page _Layout.cshtml

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    @RenderSection("metatags", false)
    <title>My ASP.NET Application</title>
</head>
<body>
    @RenderBody()
</body>
</html>

Here's the index.cshtml file

@section metatags
{
    <meta name="test" content="test"/>
    <meta name="test2" content="test"/>
}

<div>Page content</div>

The result

<html>
<head>
    <meta charset="utf-8">

    <meta name="test" content="test">
    <meta name="test2" content="test">

    <title>My ASP.NET Application</title>
</head>
<body>        

<div>Page content</div>    

</body>
</html>

Question 3

If are using nested layouts you'll need to follow this guideline:

@RenderSection in nested razor templates

The technique you're using should work, if it is not, maybe that's the reason.

But looking at the intended use in your own answer, if you only need to modify the keywords and description tags there are apis in NopCommrece for that.

In your master layout:

<meta name="description" content="@(Html.NopMetaDescription())" />
<meta name="keywords" content="@(Html.NopMetaKeywords())" />

and in the client cshtml files

@{
    Html.AddMetaDescriptionParts(Model.MetaDescription);
    Html.AddMetaKeywordParts(Model.MetaKeywords);
}

There are plenty of samples for this in the NopCommerce code.

Question 4

here is a good sample on how to dynamically creating meta tags in asp.net mvc:

public string HomeMetaTags()
{
    var strMetaTag = new StringBuilder();
    strMetaTag.AppendFormat(@"<meta content='{0}' name='Keywords'/>","Home Action Keyword");
    strMetaTag.AppendFormat(@"<meta content='{0}' name='Descption'/>", "Home Description Keyword");
    return strMetaTag.ToString();
}

public ActionResult Index()
{
    ViewBag.Message = "Welcome to ASP.NET MVC!";
    ViewBag.MetaTag = HomeMetaTags(); 
    return View();
}

<head>
    <title>@ViewBag.Title</title>
    <link href="@Url.Content("~/Content/Site.css")" rel="stylesheet" type="text/css" />
    <script src="@Url.Content("~/Scripts/jquery-1.5.1.min.js")" type="text/javascript"></script>
   @Html.Raw(ViewBag.MetaTag)
</head>