Question

I’m no guru in Razor syntax, but trying to build a generic library using a fluent-style à là Telerik’s GUI components.

I have the following pieces (approximately):

public static MyBox Box(this HtmlHelper helper)
{
    return new MyBox(helper.ViewContext);
}

and:

/// <summary>
/// http://geekswithblogs.net/shaunxu/archive/2010/04/10/lt-gt-htmlencode-ihtmlstring-and-mvchtmlstring.aspx
/// </summary>
public class MyBox : IHtmlString
{
    private readonly ViewContext _viewContext;
    private string _content;
    private string _title;

    public MyBox(ViewContext viewViewContext)
    {
        _viewContext = viewViewContext;
    }

    /// <summary>
    /// See: http://haacked.com/archive/2011/02/27/templated-razor-delegates.aspx
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public MyBox Content(Func<object, object> value)
    {
        _content = value.DynamicInvoke(_viewContext).ToString();
        return this;
    }

    /// <summary>
    /// See: http://haacked.com/archive/2011/02/27/templated-razor-delegates.aspx
    /// </summary>
    /// <param name="values"></param>
    /// <returns></returns>
    public MyBox Content(params Func<object, object>[] values)
    {
        foreach (var value in values)
        {
            _content += value.DynamicInvoke(_viewContext).ToString();
        }
        return this;
    }

    public MyBox Content(MvcHtmlString content)
    {
        _content = content.ToString();
        return this;
    }

    public MyBox Title(string title)
    {
        _title = title;
        return this;
    }

    public string ToHtmlString()
    {
        using (var stringWriter = new StringWriter())
        {
            WriteHtml((TextWriter)stringWriter);
            return stringWriter.ToString();
        }
    }

    public void Render()
    {
        using (var writer = new HtmlTextWriter(_viewContext.Writer))
            WriteHtml(writer);
    }

    protected virtual void WriteHtml(TextWriter writer)
    {
        writer.WriteLine("<!-- START BOX -->");
        writer.WriteLine("<h1>" + _title + "</h1>));
        writer.WriteLine(_content);
        writer.WriteLine("<!-- END BOX -->");
    }
}

I also have a set of Html extension methods that return MvcHtmlString’s. One example is (simplified):

public static class GuiElementExtensions
    {
        private const string FieldContainerHeadingTemplate = @"
<tr><th style=""text-align:left"" colspan=""2"">{0}</th></tr>
";

    public static MvcHtmlString GuiFieldContainerHeading(this HtmlHelper helper, string text)
        {
            return new MvcHtmlString(String.Format(FieldContainerHeadingTemplate, text));
        }
}

Then, in my .cshtml file, I do the following:

  @using (Html.BeginForm())
       {
           @(Html.Gui()
                      .Box()
                      .Title("Hello World!")
                      .Content(
                                @<h1>Hello World! This is the cool Gui.Box</h1> 
                       )
        )
 }

Which calls public MyBox Content(Func<object, object> value), and works.
Similarly, when I try the following:

  @using (Html.BeginForm())
       {
           @(Html.Gui()
                      .Box()
                      .Title("Hello World!")
                      .Content(
                                Html.GuiFieldContainerHeading("SubHeading 1")
                       )
        )
 }

It happily calls public MyBox Content(MvcHtmlString content) and works as expected.

But, however, when I try to do the following, I can’t wrap my head around how the Razor compiler engine works. How do I get it to return the sum of

• @<h1>Hello World! This is Gui().Box()</h1> (which is a Func)
• Html.GuiFieldContainerHeading("SubHeading 1") (which is an MvcHtmlString)

as either one object (be it a Func, MvcHtmlString, whatever, or a list of objects? I would like to write generic Razor syntax inside the parameter list to the Content function in my MyBox class, like this:

  @using (Html.BeginForm())
       {
           @(Html.Gui()
                      .Box()
                      .Title("Hello World!")
                      .Content(
                                @<h1>Hello World! This is Gui().Box()</h1> 
                                Html.GuiFieldContainerHeading("SubHeading 1")
                Html.TextBoxFor(model => model.Name)
                @<h2>Hello there!</h2>
                       )
        )
 }

Am I on the right track whatsoever, or is there a much simpler way of doing what I want? I want to gather all the “common gui elements” in our system in a common DLL, so not every developer in my organization needs to reinvent the wheel on each project.

Any help appreciated.

---

OK, next problem:

I have generalized the Box into a Container, and created two subclasses, Box and HighlightArea. However, using the following code, the Razor compiler kicks me with the message

Inline markup blocks (@<p>Content</p>) cannot be nested.
Only one level of inline markup is allowed.

The code not working, is:

 @(Html.Gui()
              .Box()
              .Title("BoxTitle")
              .Content(@<text>
                        <h1>Hello World! This is the box content</h1> 
                        @Html.GuiFieldContainerHeading("This is the heading")
                        @(Html.Gui().HighlightArea()
                              .Content(
                                @Html.ValidationSummary()
                                @<h1>Jalla</h1>
                              )
                        )
                       </text>
               )

Do we have a workaround for this? Or is my approach not feasible?

Answer 1

You could use the <text> tag to combine everything into one parameter.

@using (Html.BeginForm())
{
    @(Html.Gui()
        .Box()
        .Title("Hello World!")
        .Content(
            @<text>
                <h1>Hello World! This is Gui.Box</h1> 
                @Html.GuiFieldContainerHeading("SubHeading 1")
                @Html.TextBoxFor(model => model.Name)
                <h2>Hello there!</h2>
            </text>
        )
    )
}

I guess your example isn’t really working. If I’m not mistaken you could get it working like this:

@<h1>Hello World! This is Gui.Box</h1>
 + Html.GuiFieldContainerHeading("SubHeading 1")
 + Html.TextBoxFor(model => model.Name)
 + @<h2>Hello there!</h2>

But the <text> tag seems easier.