Question

When writing an htmlhelper extension if I want to support the similarly structured ctors for my htmlhelper extension method, I use RouteValueDictionary as follows:

public static string ListBoxDict(this HtmlHelper htmlHelper,                                   string name,                                   object value,                                   object htmlAttributes) {     return ListBoxDict(htmlHelper,                         name,                         value,                         ((IDictionary<string, object>)                            new RouteValueDictionary(htmlAttributes))); } 

My question really is why the need for RouteValueDictionary … I know you can’t just cast the htmlAttributes to IDictionary<string, object> … though I’m not sure why and that might be where I’m confused. Shouldn’t RouteValueDictionary be to do with Routing and therefore nothing to do with HtmlHelper methods? Like I say, I’m probably missing the point so I’d be glad if someone could tell me what I’ve missed.

Cheers…

edit: in response to Dan’s answer –>

I was just following what I had seen in use in the mvc source code for input helpers…

• see ‘src\SystemWebMvc\Mvc\Html\InputExtensions.cs‘

It does as follows:

public static string TextBox(this HtmlHelper htmlHelper,                               string name,                               object value,                               object htmlAttributes) {     return TextBox(htmlHelper,                     name,                     value,                    new RouteValueDictionary(htmlAttributes)) } 

Clearly a shortcut but is it a bastardization or is it ok to do it?

Answer 1

I would strongly recommend looking at Rob Conery’s blog post about something like this.

The meat and veg of it is this:

Codedump:

public static string ToAttributeList(this object list) {   StringBuilder sb = new StringBuilder();   if (list != null)   {     Hashtable attributeHash = GetPropertyHash(list);     string resultFormat = '{0}=\'{1}\' ';     foreach (string attribute in attributeHash.Keys)     {       sb.AppendFormat(resultFormat, attribute.Replace('_', ''),            attributeHash[attribute]);     }   }   return sb.ToString(); }  public static string ToAttributeList(this object list,                                      params object[] ignoreList) {   Hashtable attributeHash = GetPropertyHash(list);    string resultFormat = '{0}=\'{1}\' ';   StringBuilder sb = new StringBuilder();   foreach (string attribute in attributeHash.Keys)   {     if (!ignoreList.Contains(attribute))     {       sb.AppendFormat(resultFormat, attribute,            attributeHash[attribute]);     }   }   return sb.ToString(); }  public static Hashtable GetPropertyHash(object properties) {   Hashtable values = null;    if (properties != null)   {     values = new Hashtable();     PropertyDescriptorCollection props =          TypeDescriptor.GetProperties(properties);      foreach (PropertyDescriptor prop in props)     {       values.Add(prop.Name, prop.GetValue(properties));     }   }   return values; } 

Usage:

public static string ListBoxDict(this HtmlHelper htmlHelper,                                   string name,                                   object value,                                   object htmlAttributes) {     return htmlHelper.ListBoxDict(name,                                   value,                                   htmlAttributes.ToAttributeList())); } 

What .ToAttributeList() does is convert your htmlAttribute object to

name = ‘value’

Hope this makes sense.