Create Extension Method to Produce Open & Closing

问题:

I wonder if it's possible to create an extension method which has functionality & behaviour similar to Html.BeginForm(), in that it would generate a complete Html tag, and I could specificy its contents inside <% { & } %> tags.

For example, I could have a view like:

<% using(Html.BeginDiv("divId")) %>
<% { %>
    <!-- Form content goes here -->
<% } %>

This capability would be very useful in the context of the functionality I'm trying to produce with the example in this question

This would give me the ability to create containers for the types that I'll be

<% var myType = new MyType(123, 234); %>
<% var tag = new TagBuilder("div"); %>

<% using(Html.BeginDiv<MyType>(myType, tag) %>
<% { %>
    <!-- controls used for the configuration of MyType  -->
    <!-- represented in the context of a HTML element, e.g.:  -->

    <div class="MyType" prop1="123" prop2="234">
        <!-- add a select here -->
        <!-- add a radio control here -->
        <!-- whatever, it represents elements in the context of their type -->
    </div>

<% } %>

I realise this will produce invalid XHTML, but I think there could be other benefits that outweigh this, especially since this project doesn't require that the XHTML validate to the W3C standards.

Thanks

Dave

回答1:

Not quite sure how much value this has over simply defining a <div> element, but something like so

/// <summary>
/// Represents a HTML div in an Mvc View
/// </summary>
public class MvcDiv : IDisposable
{
    private bool _disposed;
    private readonly ViewContext _viewContext;
    private readonly TextWriter _writer;

    /// <summary>
    /// Initializes a new instance of the <see cref="MvcDiv"/> class.
    /// </summary>
    /// <param name="viewContext">The view context.</param>
    public MvcDiv(ViewContext viewContext) {
        if (viewContext == null) {
            throw new ArgumentNullException("viewContext");
        }
        _viewContext = viewContext;
        _writer = viewContext.Writer;
    }

    /// <summary>
    /// Performs application-defined tasks associated with 
    /// freeing, releasing, or resetting unmanaged resources.
    /// </summary>
    public void Dispose()
    {
        Dispose(true /* disposing */);
        GC.SuppressFinalize(this);
    }

    /// <summary>
    /// Releases unmanaged and - optionally - managed resources
    /// </summary>
    /// <param name="disposing"><c>true</c> to release both 
    /// managed and unmanaged resources; <c>false</c> 
    /// to release only unmanaged resources.</param>
    protected virtual void Dispose(bool disposing)
    {
        if (!_disposed)
        {
            _disposed = true;
            _writer.Write("</div>");
        }
    }

    /// <summary>
    /// Ends the div.
    /// </summary>
    public void EndDiv()
    {
        Dispose(true);
    }
}


/// <summary>
/// HtmlHelper Extension methods for building a div
/// </summary>
public static class DivExtensions
{
    /// <summary>
    /// Begins the div.
    /// </summary>
    /// <param name="htmlHelper">The HTML helper.</param>
    /// <returns></returns>
    public static MvcDiv BeginDiv(this HtmlHelper htmlHelper)
    {
        // generates <div> ... </div>>
        return DivHelper(htmlHelper, null);
    }

    /// <summary>
    /// Begins the div.
    /// </summary>
    /// <param name="htmlHelper">The HTML helper.</param>
    /// <param name="htmlAttributes">The HTML attributes.</param>
    /// <returns></returns>
    public static MvcDiv BeginDiv(this HtmlHelper htmlHelper, IDictionary<string, object> htmlAttributes)
    {
        // generates <div> ... </div>>
        return DivHelper(htmlHelper, htmlAttributes);
    }

    /// <summary>
    /// Ends the div.
    /// </summary>
    /// <param name="htmlHelper">The HTML helper.</param>
    public static void EndDiv(this HtmlHelper htmlHelper)
    {
        htmlHelper.ViewContext.Writer.Write("</div>");
    }

    /// <summary>
    /// Helps build a html div element
    /// </summary>
    /// <param name="htmlHelper">The HTML helper.</param>
    /// <param name="htmlAttributes">The HTML attributes.</param>
    /// <returns></returns>
    private static MvcDiv DivHelper(this HtmlHelper htmlHelper, IDictionary<string, object> htmlAttributes)
    {
        TagBuilder tagBuilder = new TagBuilder("div");
        tagBuilder.MergeAttributes(htmlAttributes);

        htmlHelper.ViewContext.Writer.Write(tagBuilder.ToString(TagRenderMode.StartTag));
        MvcDiv div = new MvcDiv(htmlHelper.ViewContext);

        return div;
    }
}

and use like so

<% using (Html.BeginDiv(new Dictionary<string, object>{{"class","stripey"}}))
{ %>
       <p>Content Here</p>
<% } %>

will render

<div class="stripey">
    <p>Content Here</p>
</div>

or without html attributes

<% using (Html.BeginDiv())
{ %>
       <p>Content Here</p>
<% } %>