Using sections in Editor/Display templates
Modified version of Darin's answer to ensure ordering. Also works with CSS:
public static IHtmlString Resource(this HtmlHelper HtmlHelper, Func<object, HelperResult> Template, string Type)
{
if (HtmlHelper.ViewContext.HttpContext.Items[Type] != null) ((List<Func<object, HelperResult>>)HtmlHelper.ViewContext.HttpContext.Items[Type]).Add(Template);
else HtmlHelper.ViewContext.HttpContext.Items[Type] = new List<Func<object, HelperResult>>() { Template };
return new HtmlString(String.Empty);
}
public static IHtmlString RenderResources(this HtmlHelper HtmlHelper, string Type)
{
if (HtmlHelper.ViewContext.HttpContext.Items[Type] != null)
{
List<Func<object, HelperResult>> Resources = (List<Func<object, HelperResult>>)HtmlHelper.ViewContext.HttpContext.Items[Type];
foreach (var Resource in Resources)
{
if (Resource != null) HtmlHelper.ViewContext.Writer.Write(Resource(null));
}
}
return new HtmlString(String.Empty);
}
You can add JS and CSS resources like this:
@Html.Resource(@<script src="@Url.Content("~/Scripts/jquery-1.4.4.min.js")" type="text/javascript"></script>, "js")
@Html.Resource(@<link rel="stylesheet" href="@Url.Content("~/CSS/style.css")" />, "css")
And render JS and CSS resources like this:
@Html.RenderResources("js")
@Html.RenderResources("css")
You could do a string check to see if it starts with script/link so you don't have to explicitly define what each resource is.
I liked the solution posted by @john-w-harding, so I combined it with the answer by @darin-dimitrov to make the following probably overcomplicated solution that lets you delay rendering any html (scripts too) within a using block.
USAGE
In a repeated partial view, only include the block one time:
@using (Html.Delayed(isOnlyOne: "MYPARTIAL_scripts")) {
<script>
someInlineScript();
</script>
}
In a (repeated?) partial view, include the block for every time the partial is used:
@using (Html.Delayed()) {
<b>show me multiple times, @Model.Whatever</b>
}
In a (repeated?) partial view, include the block once, and later render it specifically by name one-time:
@using (Html.Delayed("one-time", isOnlyOne: "one-time")) {
<b>show me once by name</b>
<span>@Model.First().Value</span>
}
To render:
@Html.RenderDelayed(); // the "default" unidentified blocks
@Html.RenderDelayed("one-time", false); // render the specified block by name, and allow us to render it again in a second call
@Html.RenderDelayed("one-time"); // render the specified block by name
@Html.RenderDelayed("one-time"); // since it was "popped" in the last call, won't render anything
CODE
public static class HtmlRenderExtensions {
/// <summary>
/// Delegate script/resource/etc injection until the end of the page
/// <para>@via https://stackoverflow.com/a/14127332/1037948 and http://jadnb.wordpress.com/2011/02/16/rendering-scripts-from-partial-views-at-the-end-in-mvc/ </para>
/// </summary>
private class DelayedInjectionBlock : IDisposable {
/// <summary>
/// Unique internal storage key
/// </summary>
private const string CACHE_KEY = "DCCF8C78-2E36-4567-B0CF-FE052ACCE309"; // "DelayedInjectionBlocks";
/// <summary>
/// Internal storage identifier for remembering unique/isOnlyOne items
/// </summary>
private const string UNIQUE_IDENTIFIER_KEY = CACHE_KEY;
/// <summary>
/// What to use as internal storage identifier if no identifier provided (since we can't use null as key)
/// </summary>
private const string EMPTY_IDENTIFIER = "";
/// <summary>
/// Retrieve a context-aware list of cached output delegates from the given helper; uses the helper's context rather than singleton HttpContext.Current.Items
/// </summary>
/// <param name="helper">the helper from which we use the context</param>
/// <param name="identifier">optional unique sub-identifier for a given injection block</param>
/// <returns>list of delayed-execution callbacks to render internal content</returns>
public static Queue<string> GetQueue(HtmlHelper helper, string identifier = null) {
return _GetOrSet(helper, new Queue<string>(), identifier ?? EMPTY_IDENTIFIER);
}
/// <summary>
/// Retrieve a context-aware list of cached output delegates from the given helper; uses the helper's context rather than singleton HttpContext.Current.Items
/// </summary>
/// <param name="helper">the helper from which we use the context</param>
/// <param name="defaultValue">the default value to return if the cached item isn't found or isn't the expected type; can also be used to set with an arbitrary value</param>
/// <param name="identifier">optional unique sub-identifier for a given injection block</param>
/// <returns>list of delayed-execution callbacks to render internal content</returns>
private static T _GetOrSet<T>(HtmlHelper helper, T defaultValue, string identifier = EMPTY_IDENTIFIER) where T : class {
var storage = GetStorage(helper);
// return the stored item, or set it if it does not exist
return (T) (storage.ContainsKey(identifier) ? storage[identifier] : (storage[identifier] = defaultValue));
}
/// <summary>
/// Get the storage, but if it doesn't exist or isn't the expected type, then create a new "bucket"
/// </summary>
/// <param name="helper"></param>
/// <returns></returns>
public static Dictionary<string, object> GetStorage(HtmlHelper helper) {
var storage = helper.ViewContext.HttpContext.Items[CACHE_KEY] as Dictionary<string, object>;
if (storage == null) helper.ViewContext.HttpContext.Items[CACHE_KEY] = (storage = new Dictionary<string, object>());
return storage;
}
private readonly HtmlHelper helper;
private readonly string identifier;
private readonly string isOnlyOne;
/// <summary>
/// Create a new using block from the given helper (used for trapping appropriate context)
/// </summary>
/// <param name="helper">the helper from which we use the context</param>
/// <param name="identifier">optional unique identifier to specify one or many injection blocks</param>
/// <param name="isOnlyOne">extra identifier used to ensure that this item is only added once; if provided, content should only appear once in the page (i.e. only the first block called for this identifier is used)</param>
public DelayedInjectionBlock(HtmlHelper helper, string identifier = null, string isOnlyOne = null) {
this.helper = helper;
// start a new writing context
((WebViewPage)this.helper.ViewDataContainer).OutputStack.Push(new StringWriter());
this.identifier = identifier ?? EMPTY_IDENTIFIER;
this.isOnlyOne = isOnlyOne;
}
/// <summary>
/// Append the internal content to the context's cached list of output delegates
/// </summary>
public void Dispose() {
// render the internal content of the injection block helper
// make sure to pop from the stack rather than just render from the Writer
// so it will remove it from regular rendering
var content = ((WebViewPage)this.helper.ViewDataContainer).OutputStack;
var renderedContent = content.Count == 0 ? string.Empty : content.Pop().ToString();
// if we only want one, remove the existing
var queue = GetQueue(this.helper, this.identifier);
// get the index of the existing item from the alternate storage
var existingIdentifiers = _GetOrSet(this.helper, new Dictionary<string, int>(), UNIQUE_IDENTIFIER_KEY);
// only save the result if this isn't meant to be unique, or
// if it's supposed to be unique and we haven't encountered this identifier before
if( null == this.isOnlyOne || !existingIdentifiers.ContainsKey(this.isOnlyOne) ) {
// remove the new writing context we created for this block
// and save the output to the queue for later
queue.Enqueue(renderedContent);
// only remember this if supposed to
if(null != this.isOnlyOne) existingIdentifiers[this.isOnlyOne] = queue.Count; // save the index, so we could remove it directly (if we want to use the last instance of the block rather than the first)
}
}
}
/// <summary>
/// <para>Start a delayed-execution block of output -- this will be rendered/printed on the next call to <see cref="RenderDelayed"/>.</para>
/// <para>
/// <example>
/// Print once in "default block" (usually rendered at end via <code>@Html.RenderDelayed()</code>). Code:
/// <code>
/// @using (Html.Delayed()) {
/// <b>show at later</b>
/// <span>@Model.Name</span>
/// etc
/// }
/// </code>
/// </example>
/// </para>
/// <para>
/// <example>
/// Print once (i.e. if within a looped partial), using identified block via <code>@Html.RenderDelayed("one-time")</code>. Code:
/// <code>
/// @using (Html.Delayed("one-time", isOnlyOne: "one-time")) {
/// <b>show me once</b>
/// <span>@Model.First().Value</span>
/// }
/// </code>
/// </example>
/// </para>
/// </summary>
/// <param name="helper">the helper from which we use the context</param>
/// <param name="injectionBlockId">optional unique identifier to specify one or many injection blocks</param>
/// <param name="isOnlyOne">extra identifier used to ensure that this item is only added once; if provided, content should only appear once in the page (i.e. only the first block called for this identifier is used)</param>
/// <returns>using block to wrap delayed output</returns>
public static IDisposable Delayed(this HtmlHelper helper, string injectionBlockId = null, string isOnlyOne = null) {
return new DelayedInjectionBlock(helper, injectionBlockId, isOnlyOne);
}
/// <summary>
/// Render all queued output blocks injected via <see cref="Delayed"/>.
/// <para>
/// <example>
/// Print all delayed blocks using default identifier (i.e. not provided)
/// <code>
/// @using (Html.Delayed()) {
/// <b>show me later</b>
/// <span>@Model.Name</span>
/// etc
/// }
/// </code>
/// -- then later --
/// <code>
/// @using (Html.Delayed()) {
/// <b>more for later</b>
/// etc
/// }
/// </code>
/// -- then later --
/// <code>
/// @Html.RenderDelayed() // will print both delayed blocks
/// </code>
/// </example>
/// </para>
/// <para>
/// <example>
/// Allow multiple repetitions of rendered blocks, using same <code>@Html.Delayed()...</code> as before. Code:
/// <code>
/// @Html.RenderDelayed(removeAfterRendering: false); /* will print */
/// @Html.RenderDelayed() /* will print again because not removed before */
/// </code>
/// </example>
/// </para>
/// </summary>
/// <param name="helper">the helper from which we use the context</param>
/// <param name="injectionBlockId">optional unique identifier to specify one or many injection blocks</param>
/// <param name="removeAfterRendering">only render this once</param>
/// <returns>rendered output content</returns>
public static MvcHtmlString RenderDelayed(this HtmlHelper helper, string injectionBlockId = null, bool removeAfterRendering = true) {
var stack = DelayedInjectionBlock.GetQueue(helper, injectionBlockId);
if( removeAfterRendering ) {
var sb = new StringBuilder(
#if DEBUG
string.Format("<!-- delayed-block: {0} -->", injectionBlockId)
#endif
);
// .count faster than .any
while (stack.Count > 0) {
sb.AppendLine(stack.Dequeue());
}
return MvcHtmlString.Create(sb.ToString());
}
return MvcHtmlString.Create(
#if DEBUG
string.Format("<!-- delayed-block: {0} -->", injectionBlockId) +
#endif
string.Join(Environment.NewLine, stack));
}
}
You could proceed with a conjunction of two helpers:
public static class HtmlExtensions
{
public static MvcHtmlString Script(this HtmlHelper htmlHelper, Func<object, HelperResult> template)
{
htmlHelper.ViewContext.HttpContext.Items["_script_" + Guid.NewGuid()] = template;
return MvcHtmlString.Empty;
}
public static IHtmlString RenderScripts(this HtmlHelper htmlHelper)
{
foreach (object key in htmlHelper.ViewContext.HttpContext.Items.Keys)
{
if (key.ToString().StartsWith("_script_"))
{
var template = htmlHelper.ViewContext.HttpContext.Items[key] as Func<object, HelperResult>;
if (template != null)
{
htmlHelper.ViewContext.Writer.Write(template(null));
}
}
}
return MvcHtmlString.Empty;
}
}
and then in your _Layout.cshtml:
<body>
...
@Html.RenderScripts()
</body>
and somewhere in some template:
@Html.Script(
@<script src="@Url.Content("~/Scripts/jquery-1.4.4.min.js")" type="text/javascript"></script>
)
I faced the same problem, but solutions proposed here work good only for adding reference to the resource and are not very suitable for inline JS code. I found a very helpful article and wrapped all my inline JS (and also script tags) in
@using (Html.BeginScripts())
{
<script src="@Url.Content("~/Scripts/jquery-ui-1.8.18.min.js")" type="text/javascript"></script>
<script>
// my inline scripts here
<\script>
}
And in the _Layout view placed @Html.PageScripts() just before closing 'body' tag. Works like a charm for me.
The helpers themselves:
public static class HtmlHelpers
{
private class ScriptBlock : IDisposable
{
private const string scriptsKey = "scripts";
public static List<string> pageScripts
{
get
{
if (HttpContext.Current.Items[scriptsKey] == null)
HttpContext.Current.Items[scriptsKey] = new List<string>();
return (List<string>)HttpContext.Current.Items[scriptsKey];
}
}
WebViewPage webPageBase;
public ScriptBlock(WebViewPage webPageBase)
{
this.webPageBase = webPageBase;
this.webPageBase.OutputStack.Push(new StringWriter());
}
public void Dispose()
{
pageScripts.Add(((StringWriter)this.webPageBase.OutputStack.Pop()).ToString());
}
}
public static IDisposable BeginScripts(this HtmlHelper helper)
{
return new ScriptBlock((WebViewPage)helper.ViewDataContainer);
}
public static MvcHtmlString PageScripts(this HtmlHelper helper)
{
return MvcHtmlString.Create(string.Join(Environment.NewLine, ScriptBlock.pageScripts.Select(s => s.ToString())));
}
}