Why use TagBuilder instead of StringBuilder?

Question

what's the difference in using tag builder and string builder to create a table in a htmlhelper class, or using the HtmlTable?

aren't they generating the same thing??

Schrader

Answer 1

TagBuilder is a class that specially designed for creating html tags and their content. You are right saying that result will be anyway a string and of course you still can use StringBuilder and the result will be the same, but you can do things easier with TagBuilder. Lets say you need to generate a tag:

<a href='http://www.stackoverflow.com' class='coolLink'/>

Using StringBuilder you need to write something like this:

var sb = new StringBuilder();
sb.Append("<a href='");
sb.Append(link);
sb.Append("' class = '");
sb.Append(ccsClass);
sb.Append("'/>");
sb.ToString();

It is not very cool, isn’t it? And compare how you can build it using TagBuilder;

var tb = new TagBuilder("a");
tb.MergeAttribute("href",link);
tb.AddCssClass(cssClass);
tb.ToString(TagRenderMode.SelfClosing);

Isn't that better?

Profundity

For simple tags as per above I prefer sb.AppendFormat("<a href='{0}' class = '{1}'/>", link, cssClass); but the methods on TagBuilder are really neat if one needs more complex tags. – Gil

Note he asked about building a table, i.e. he's probably nesting table, tbody and then multiple trs and tds. Won't he need one tagbuilder for each of those? I expect that'll get a lot messier than the equivalent stringbuilder. – Spirant

"<a href='" + link + "' class='" + class + "' />" is even more cleaner. And it's fast because 1) string concatenation is quite fast, with end-result being single string anyway, and 2) don't optimize prematurely. For more complex cases (like tables) I'd suggest templating engine like Spark. I've seen sources that use TagBuilder and that's still hard to understand. – Mazurek

@Spirant Actually if you make the right extension methods it's actually much cleaner to use a semantic model like TagBuilder for generating nested tags. – Arsenite

Why not use StringBuilder to build your attributes and spit out the tags as needed like so: <a href='stackoverflow.com' @attributes /> – Induration

"<a href='\{link}' class='\{cssClass}'/>" is even cleaner, but does not scale like using a TagBuilder does – Chewy

@Mazurek Your example is not best practice as it is a very poor habit to concatenate strings regardless of their length. Strings are placed on the heap where StringBuilder uses the stack. Concatenating string means your app is reallocating new heap resources upon every string addition and the previous allocations are left sitting out their until .NET decides to garbage collect = wasted memory. – Aubreir

@Joshua See #21578 for explanation of when + is better than StringBuilder as in my example. – Mazurek

Answer 2

It's just convenience. From this tutorial:

You don’t really need to use the TagBuilder class. You could use a StringBuilder class instead. However, the TagBuilder class makes your life a little easier.

Look at the methods on TagBuilder, and think about whether they give you value. would you want to do the same thing yourself manually in StringBuilder every time? Is there escaping that it does for you? Attribute merging, etc? Is the resulting code easier to read, making it clearer that you're building a tag rather than some arbitrary string?

Zindman

I think using TagBuilder defeats the purpose of MVC. You're mixing code and markup for the sake of brevity at the expense of easier modification. – Induration

@Joel Rodgers TagBuilder has it's place in HtmlHelpers – Thorough

And some point you'll get angry at tag builder and implement your own where you mostly reuse tag builder. – Gymno

@ChrisMarisic TagBuilder isn't a sealed class. You can see a coupable chainable derived classes floating around on the Web. – Interfertile

@JoelRodgers I think if your template has enough conditional stuff in it that it's starting to look more like C# code than HTML then the tag builders start to seem like they make a lot of sense. – Interfertile

@emodendroket the tag builder is highly opinionated and anti-extensible, you'll find out if you ever try to extend it. Then you'll copy paste the source and make your own instead. – Gymno

@ChrisMarisic Well, I have, and that wasn't my experience, but that's fine. – Interfertile

Answer 3

There's a point that the other answers have missed so far. If you return TagBuilder from an extension method you can continue to add attributes in your view. Let's say you were returning a table from an Html helper and you want to add a class attribute. If you're using a StringBuilder you need to pass the class in as a parameter.

public static string Table(...., string @class)
{
    ...
    sb.AppendFormat("class='{0}", @class);
    ...
}

// In the view
<%: Html.Table(someParams, "fancy") %>

But adding a class attribute to an HTML tag is not the concern of an extension method that creates a table! If we switch to a semantic model (TagBuilder) for generating the HTML, we can add the class attribute outside of the table method.

public static TagBuilder Table(....)
{
    ...
    return tag;
}

// In the view
<%: Html.Table(someParams).AddCssClass("fancy") %>

In addition to TagBuilder, you might want to check out FubuMVC's HtmlTags library. It's a much better model for generating HTML. I have some more details on blog.

Arsenite

Answer 4

aren't they generating the same thing??

Well, sure, but that shouldn't be a deterrent, should it? One class is designed for something more specific than the other, so it offers a greater level of convenience.

I could ask: why use a StringBuilder? Why not a List<char>? Couldn't I generate the same thing from either?

Going one step further: why even a List<char>? Why not just a char[], the resizing/manipulation of which I can control myself? I can still totally create a string from a char[].

In fact, all I really need is a char* and an int (for length). Right?

My point is just that if a class is available for specialized functionality that you can use, it makes sense to use it if you ask me.

Longways

Answer 5

As it is mentioned in the other posts, TagBuilder brings some convenience. But you should consider that TagBuilder and StringBuilder may does not produce the same result. TagBuilder applies html encoding, but StringBuilder doesn't. So it is safer to use TagBuilder to overcome vulnerabilies that may be exploited via XSS attack.

Norge

Answer 6

Don't forget to do HTML encoding of values if you are using StringBuilder. I hope TagBuilder do this automatically.

Trapeziform