I'm looking for a way to write the following code with less lines of code (maybe 5). I suppose I could do the same thing as the selected class but this razor syntax isn't looking pretty.
<ul>
@foreach (var mi in Model.MenuItems) {
<li@(mi.Selected?" class=\"selected\"":null)>
@if (string.IsNullOrEmpty(mi.Title)) {
<a href="@mi.Href">@mi.Text</a>
} else {
<a href="@mi.Href" title="@mi.Title">@mi.Text</a>
}
</li>
}
</ul>
see http://weblogs.asp.net/jgalloway/archive/2012/02/16/asp-net-4-beta-released.aspx
Conditional attribute rendering
If you have an attribute that might be null, in the past you've needed to do a null check to avoid writing out an empty attribute, like this:
<div @{if (myClass != null) { <text>class="@myClass"</text> } }>Content</div>
Now Razor is able to handle that automatically, so you can just write out the attribute. If it's null, the attribute isn't written:
<div class="@myClass">Content</div>
So if @myClass is null, the output is just this:
<div>Content</div>
display:none for example. Or do I still need to use that ugly conditional?
var trstyle = index == 0 ? "display: none;" : null;, then in the tr itself I do <tr style="@trstyle">, which makes the first row hidden (index == 0). The output is simply <tr> for the other rows. Worked beautifully. +1.
data-xxx attributes, though. Aaargh.... Inconsistencies....I've come up with a chainable HtmlAttribute class and some Html Extension methods to allow the Razor syntax below:
<ul>
@foreach (var mi in items) {
<li @Html.Css("selected", mi.Selected)>
<a href="@mi.Href" @Html.Attr("title", mi.Title)>@mi.Text</a>
</li>
}
</ul>
Here is the HtmlAttribute class:
public class HtmlAttribute : IHtmlString
{
private string _InternalValue = String.Empty;
private string _Seperator;
public string Name { get; set; }
public string Value { get; set; }
public bool Condition { get; set; }
public HtmlAttribute(string name)
: this(name, null)
{
}
public HtmlAttribute( string name, string seperator )
{
Name = name;
_Seperator = seperator ?? " ";
}
public HtmlAttribute Add(string value)
{
return Add(value, true);
}
public HtmlAttribute Add(string value, bool condition)
{
if (!String.IsNullOrWhiteSpace(value) && condition)
_InternalValue += value + _Seperator;
return this;
}
public string ToHtmlString()
{
if (!String.IsNullOrWhiteSpace(_InternalValue))
_InternalValue = String.Format("{0}=\"{1}\"", Name, _InternalValue.Substring(0, _InternalValue.Length - _Seperator.Length));
return _InternalValue;
}
}
Extra info: The "seperator" is used to chain together multiple values for an attribute. This can be useful for multiple css class names (use a space) or perhaps use String.Empty to build an value dependant on multiple conditions (by using the .Add() method)
And here are the Html Extension helper methods:
public static class Extensions
{
public static HtmlAttribute Css(this HtmlHelper html, string value)
{
return Css(html, value, true);
}
public static HtmlAttribute Css(this HtmlHelper html, string value, bool condition)
{
return Css(html, null, value, condition);
}
public static HtmlAttribute Css(this HtmlHelper html, string seperator, string value, bool condition)
{
return new HtmlAttribute("class", seperator).Add(value, condition);
}
public static HtmlAttribute Attr(this HtmlHelper html, string name, string value)
{
return Attr(html, name, value, true);
}
public static HtmlAttribute Attr(this HtmlHelper html, string name, string value, bool condition)
{
return Attr(html, name, null, value, condition);
}
public static HtmlAttribute Attr(this HtmlHelper html, string name, string seperator, string value, bool condition)
{
return new HtmlAttribute(name, seperator).Add(value, condition);
}
}
Let me know if they are of use.
Thanks,
Lee
<ul>
@foreach (var mi in Model.MenuItems) {
<li@(mi.Selected?" class=\"selected\"":null)>
<a href="@mi.Href" @{if(!string.IsNullOrEmpty(mi.Title)) { <text>title="@mi.Title"</text>} }>@mi.Text</a>
</li>
}
</ul>
I haven't tested it but it parses correctly.
That would be a good candidate for custom HTML helper:
public static class HtmlExtensions
{
public static MvcHtmlString MenuItem(this HtmlHelper htmlHelper, MenuItem mi)
{
var li = new TagBuilder("li");
if (mi.Selected)
{
li.AddCssClass("selected");
}
var a = new TagBuilder("a");
a.MergeAttribute("href", mi.Href);
if (!string.IsNullOrEmpty(mi.Title))
{
a.MergeAttribute("title", mi.Title);
}
a.SetInnerText(mi.Text);
return MvcHtmlString.Create(li.ToString());
}
}
and in your view:
<ul>
@foreach (var mi in Model.MenuItems) {
@Html.MenuItem(mi)
}
</ul>
or using DisplayTemplates you don't even need to write a loop:
<ul>
@Html.DisplayFor(x => x.MenuItems)
</ul>
<ul>
@foreach (var mi in Model.MenuItems) {
<li@(Html.Raw((mi.Selected ? " class=\"selected\"" : null))>
<a href="@mi.Href">@mi.Text</a>
</li>
}
</ul>
class attribute would not be rendered by Razor if value is null
<a href="#nolink" class="@(categoryId == null ? "submenu-active": null)">All</a>
For the case of multiple classes I use this simple extension method:
public static MvcHtmlString If(this string text, bool condition) {
return new MvcHtmlString(condition ? text : string.Empty);
}
And in the view:
<div class="menuitem @("active".If(Model.Active))">
It's really pretty simple and clean:
<p @(cssClass != null) ? { class="@cssClass" }> Stuff and whatnot... </p>
