ASP.NET MVC: Page-specific logic

Question

There has been many discussion on ASP.NET MVC and Codebehind-files, mostly where it has been pointed out that these Codebehind-files are evil.

So my question is, how do you handle page-specific logic?

What we don't want here is spaghetti-code in the inline-code and we don't want page-specific code scattered throughout helper-classes or on top of the HTML-helper-class.

An example would be:

<% for(int i = 0; i < companyList.Count; i++) { %>
    RenderCompanyNameWithRightCapsIfNotEmpty(company, i)
<% } %>

With accompanying codebehind:

private string RenderCompanyNameWithRightCapsIfNotEmpty(string company, index)
{
    if (index == 0) {
        return string.Format("<div class=\"first\">{0}</div>", company);
    }
    // Add more conditional code here
    // - page specific HTML, like render a certain icon
    string divClass = (index % 2 == 0) ? "normal" : "alternate";
    return string.Format("<div class=\"{1}\">{0}</div>", company, divClass);
}

This will only be used on one page and is most likely subject to change.

Update: A couple approaches I thought about where these:

1) Inline codebehind on page - with simple methods that returns strings.

<script runat="server">
    private string RenderCompanyHtml(string companyName) ...
<script>

2) Putting a method which returns a string in the Controller. But that would be putting View-logic into the Controller.

public class SomeController : Controller 
{
    [NonAction] 
    private static string RenderCompanyHtml(string companyName) ...

    public ActionResult Index() ...
}

Answer 1

You should put that code in the controlleraction where you prepare the viewdata.

I usually make a region "helper methods" in my controller class with a few [NonAction] methods to keep things clean.

So my (simplified) controller would look like this:

public class SomeController : Controller 
{
  #region Helper methods
  [NonAction] 
  private static string CompanyNameWithRightCapsIfNotEmpty(string company)
  {
    if (string.IsNullOrEmpty(company)) {
        return company;
    }
    return UpperCaseSpecificWords(company);
  }

  #endregion

  public ActionResult Companies()
  {
    var companies = GetCompanies();
    var companyNames = companies.Select(c =>  CompanyNameWithRightCapsIfNotEmpty(c.Name));
    ViewData["companyNames"] = companyNames;
    return view();
  }
}

Answer 2

Use Html Helpers.

Like so create the helper methods in a static class:

    public static string Label(this HtmlHelper helper, string target, string text)
    {
        return String.Format("<label for='{0}'>{1}</label>", target, text);
    }

.. then use in your view:

<span><% =Html.Label("FinishDateTime.LocalDatetime", "Finish Time:")%><br />

You could create a helper method called maybe RenderCompanyName(string[] companies) that checked for nulls, did the caps manipulation and rendered the html in between - all in the same helper if you like.

Also: controller action methods should be light - ie. only getting the data and returning views. You should delegate things like manipulation of data for presentation to views and Html helpers.

EDIT: Here is a helper that you might be after:

This helper renders an IList<> to html in the form of an unordered list <ul>...</ul>. The useful thing about it is that it gives you control over how the list is rendered thru css AND it allows you to render additional html/content for each item. Take a look - this is the helper:

    public static string UnorderedList<TItem>(this HtmlHelper helper,
        IList<TItem> items, Func<TItem, string> renderItemHtml,
        string ulID, string ulClass, string liClass)
    {
        StringBuilder sb = new StringBuilder();

        // header
        if (!ulID.IsNullOrTrimEmpty()) sb.AppendFormat("<ul id='{0}'", helper.Encode(ulID.Trim()));
        else sb.AppendFormat("<ul");
        if (!ulClass.IsNullOrTrimEmpty()) sb.AppendFormat(" class='{0}'>", helper.Encode(ulClass.Trim()));
        else sb.AppendFormat(">");

        // items
        foreach (TItem i in items)
        {
            if (!liClass.IsNullOrTrimEmpty())
                sb.AppendFormat("<li class='{0}'>{1}</li>", helper.Encode(liClass.Trim()),
                    renderItemHtml(i));
            else
                sb.AppendFormat("<li>{0}</li>", renderItemHtml(i));
        }

        // footer
        sb.AppendFormat("</ul>");

        return sb.ToString();
    }

..using it is easy. here is a simple example to render a list of tags:

    <div id="tags">
        <h2>Tags</h2>
        <%=Html.UnorderedList<Tag>(Model.Tags.Tags,tag=>
            {
                return tag.Name;
            },null,null,null) %>
    </div>

..you can see in my usage example that i have chosen not to specify any css or id attribute and i simply return the name of the Tag item thru the use of the anonymous delegate. Anonymous delegates are way easy to use.. in your case maybe something like this would work:

    <div id="tags">
        <h2>Tags</h2>
        <%=Html.UnorderedList<string>(ViewData["companies"],company=>
            {
                if (someCondition) return company.ToUpper();
                else return company;
            },null,null,null) %>
    </div>

.. ViewData["companies"] is an IList<string> for simplicity.

Answer 3

Helper methods are one good way of handling page specific code, but I think it is a;ways preferable to get your model to show the data you need.

If you're going to go for the helper option, you would be better served by making the operation it perfroms a bit less page specific. If your method RenderCompanyNameWithRightCapsIfNotEmpty has to be so specific it would be better if your model provided it. One way would be to have the model provide a list with the text already formatted, and expose it as a public property (say an IEnumerable of formatted company names).