Ramstack.HtmxToolkit 1.1.0

HtmxToolkit

Provides HTMX integration for ASP.NET Core applications.

• Getting Started
• HttpRequest
  • HtmxRequestAttribute
• HttpResponse
  • The declarative way of setting response headers
• TagHelpers
  • HtmxUrlTagHelper
  • HtmxHeaderTagHelper
  • HtmxConfigTagHelper
• Antiforgery Token
• License

Getting Started

Install Ramstack.HtmxToolkit NuGet package to your project, use the following command

dotnet add package Ramstack.HtmxToolkit

HttpRequest

The library provides a set of classes for working with HttpRequest. First off, there's the HttpRequestExtensions class.

/// <summary>
/// Provides extension methods for the <see cref="HttpRequest"/> class.
/// </summary>
public static class HttpRequestExtensions
{
    /// <summary>
    /// Determines whether the specified HTTP request is htmx request.
    /// </summary>
    /// <param name="request">The HTTP request.</param>
    /// <returns>
    /// <c>true</c> if the specified HTTP request is htmx request; otherwise, <c>false</c>.
    /// </returns>
    public static bool IsHtmxRequest(this HttpRequest request);

    /// <summary>
    /// Determines whether the specified HTTP request is htmx request.
    /// </summary>
    /// <param name="request">The HTTP request.</param>
    /// <param name="headers">When this methods returns, contains the <see cref="HtmxRequestHeaders"/>
    /// that provides well-known htmx headers.</param>
    /// <returns>
    /// <c>true</c> if the specified HTTP request is htmx request; otherwise, <c>false</c>.
    /// </returns>
    public static bool IsHtmxRequest(this HttpRequest request, out HtmxRequestHeaders headers);

    /// <summary>
    /// Determines whether the specified HTTP request was made using AJAX
    /// instead of a normal navigation.
    /// </summary>
    /// <param name="request">The HTTP request.</param>
    /// <returns>
    /// <c>true</c> if the specified HTTP request is boosted; otherwise, <c>false</c>.
    /// </returns>
    public static bool IsHtmxBoosted(this HttpRequest request);

    /// <summary>
    /// Determines whether the specified HTTP request was made using AJAX
    /// instead of a normal navigation.
    /// </summary>
    /// <param name="request">The HTTP request.</param>
    /// <param name="headers">When this methods returns, contains the <see cref="HtmxRequestHeaders"/>
    /// that provides well-known htmx headers.</param>
    /// <returns>
    /// <c>true</c> if the specified HTTP request is boosted; otherwise, <c>false</c>.
    /// </returns>
    public static bool IsHtmxBoosted(this HttpRequest request, out HtmxRequestHeaders headers);

    /// <summary>
    /// Returns the <see cref="HtmxRequestHeaders"/> that provides well-known htmx headers.
    /// </summary>
    /// <param name="request">The HTTP request.</param>
    /// <returns>
    /// The <see cref="HtmxRequestHeaders"/>.
    /// </returns>
    public static HtmxRequestHeaders GetHtmxHeaders(this HttpRequest request);
}

The IsHtmxRequest method allows you to determine whether the current request is initiated by HTMX.

HttpContext.Request.IsHtmxRequest()

And thus, you can define different scenarios depending on the result, for example:

if (Request.IsHtmxRequest())
    return PartialView();

return View();

The overloads of these methods provide access to strongly typed headers set by HTMX:

if (Request.IsHtmxRequest(out var headers))
{
    if (headers.HistoryRestoreRequest)
    {
        ...
    }
}

In addition, access to strongly typed headers can be obtained by calling GetHtmxHeaders:

var headers = Request.GetHtmxHeaders();

The full list of headers is presented below:

/// <summary>
/// Represents strongly typed HTMX request headers.
/// </summary>
public readonly struct HtmxRequestHeaders
{
    /// <summary>
    /// Gets a value indicating whether the request
    /// was made using AJAX instead of a normal navigation.
    /// </summary>
    public bool Boosted { get; }

    /// <summary>
    /// Gets the current URL of the browser.
    /// </summary>
    public string? CurrentUrl { get; }

    /// <summary>
    /// Gets a value indicating whether the request
    /// is for history restoration after a miss in the local history cache.
    /// </summary>
    public bool HistoryRestoreRequest { get; }

    /// <summary>
    /// Gets the user response to an hx-prompt on the client.
    /// </summary>
    public string? Prompt { get; }

    /// <summary>
    /// Gets a value indicating whether the current request is htmx request.
    /// </summary>
    public bool Request { get; }

    /// <summary>
    /// Gets the ID of the target element if it exists.
    /// </summary>
    public string? Target { get; }

    /// <summary>
    /// Gets the name of the triggered element if it exists.
    /// </summary>
    public string? TriggerName { get; }

    /// <summary>
    /// Gets the ID of the triggered element if it exists
    /// as indicated by the <c>HX-Trigger</c> header.
    /// </summary>
    public string? Trigger { get; }
}

Example of usage:

if (Request.GetHtmxHeaders().IsHistoryRestoreRequests)
{
    ...
}

The library also provides a set of predefined string constants for request headers, so you don't have to remember them each time and risk making mistakes in spelling. You can find them in the HtmxRequestHeaderNames class.

/// <summary>
/// Defines constants for the well-known names of htmx request headers.
/// For more information, see https://htmx.org/reference/#request_headers
/// </summary>
public static class HtmxRequestHeaderNames
{
    /// <summary>
    /// The <c>HX-Boosted</c> header indicates whether the request was made using AJAX
    /// instead of a normal navigation.
    /// </summary>
    public const string Boosted = "HX-Boosted";

    /// <summary>
    /// The <c>HX-Current-URL</c> header contains the current URL of the browser.
    /// </summary>
    public const string CurrentUrl = "HX-Current-URL";

    ...
    // The list of other constants is omitted for brevity
}

HtmxRequestAttribute

To simplify some manual checks, the library provides an ASP.NET Core result filter that can be applied to an action controller, page handler, or the entire controller:

public class UserController : ControlleBase
{
    [HtmxRequest]
    public IActionResult UpdateProfile(UserProfile profile)
    {
        ...
    }
}

If you are processing boosted requests in a special way, add the Boosted parameter.

public class UserController : ControlleBase
{
    ...
    [HtmxRequest(Boosted = true)]
    public IActionResult UpdateProfile(UserProfile profile)
    {
        ...
    }
}

HttpResponse

For working with response headers, the library also provides a set of classes. The first one is the HttpResponseExtension class with extension methods:

/// <summary>
/// Provides extension methods for the <see cref="HttpResponse"/> class.
/// </summary>
public static class HttpResponseExtensions
{
    /// <summary>
    /// Returns the <see cref="HtmxResponseHeaders"/> that provides well-known htmx headers.
    /// </summary>
    /// <param name="response">The HTTP response.</param>
    /// <returns>
    /// The <see cref="HtmxResponseHeaders"/>.
    /// </returns>
    public static HtmxResponseHeaders GetHtmxHeaders(this HttpResponse response);

    /// <summary>
    /// Configures the htmx response headers.
    /// </summary>
    /// <param name="response">The HTTP response to configure.</param>
    /// <param name="configure">The function to configure the htmx response headers.</param>
    public static void Htmx(this HttpResponse response, Action<HtmxResponse> configure);
    }

    /// <summary>
    /// Configures the htmx response headers.
    /// </summary>
    /// <param name="response">The HTTP response to configure.</param>
    /// <param name="configure">The function to configure the htmx response headers.</param>
    /// <param name="state">The value to pass to the <paramref name="configure"/>.</param>
    public static void Htmx<TState>(this HttpResponse response, Action<HtmxResponse, TState> configure, TState state);
}

The GetHtmxHeaders method provides access to strongly typed response headers that control HTMX behavior.

/// <summary>
/// Represents strongly typed HTMX response headers.
/// </summary>
public sealed class HtmxResponseHeaders
{
    /// <summary>
    /// Gets or sets the <c>HX-Location</c> header to a client-side redirect
    /// that does not do a full page reload.
    /// </summary>
    [MaybeNull]
    public string Location { get; set; }

    /// <summary>
    /// Gets or sets the <c>HX-Push-Url</c> header to push a new URL into the history stack.
    /// </summary>
    [MaybeNull]
    public string PushUrl { get; set; }

    ...
    // The remaining properties are omitted for brevity
}

Just like HtmxRequestHeaderNames, which consists of predefined string constants for HTMX request headers, there is a corresponding HtmxResponseHeaderNames class containing a list of string constants for HTMX response headers.

/// <summary>
/// Defines constants for the well-known names of htmx response headers.
/// For more information, see https://htmx.org/reference/#response_headers
/// </summary>
public static class HtmxResponseHeaderNames
{
    /// <summary>
    /// The <c>HX-Location</c> header is used to a client-side redirect that does not do a full page reload.
    /// </summary>
    public const string Location = "HX-Location";

    /// <summary>
    /// The <c>HX-Push-Url</c> header is used to push a new URL into the history stack.
    /// </summary>
    public const string PushUrl = "HX-Push-Url";

    /// <summary>
    /// The <c>HX-Redirect</c> header is used to client-side redirect to a new location.
    /// </summary>
    public const string Redirect = "HX-Redirect";

    ...
    // The list of other constants is omitted for brevity
}

However, the most convenient and efficient way is by using one of the provided Htmx methods with a callback that accepts HtmxResponse, allowing you to specify response headers in a fluent style:

Response.Htmx(headers => headers
    .TriggerEvent(
        eventName: "process",
        detail: new { Value = ... })
    .StopPolling(ShouldStopPolling));

💡 The second Htmx method accepts an additional parameter to avoid unnecessary allocations due to closures:

Response.Htmx(
    static (headers, stop) => headers
        .TriggerEvent(
            eventName: "process",
            detail: new { Value = ... })
        .StopPolling(stop),
    ShouldStopPolling);

💡 The Htmx extension methods are also available for IActionResult, allowing you to write:

return Json(profile).Htmx(h => h.StopPolling(ShouldStopPolling));

In both cases, the headers will be set only in the case of an htmx request. In the case of a regular request, the callback passed to the Htmx(this) method will not be executed, which allows avoiding unnecessary work.

The declarative way of setting response headers

Some of the response headers can be set declaratively using the HtmxResponseAttribute, which is applied to the controller, action, or page.

public class UserController : ControlleBase
{
    [HtmxRequest]
    [HtmxResponse(
        StopPolling = true,
        Reswap = HtmxSwap.OuterHtml)]
    public IActionResult UpdateProfile(UserProfile profile)
    {
        ...
    }
}

💡 If a more complex expression is needed for swap, for example, innerHTML show:#result:top, you can use the Reswap method in the HtmxResponse class, which accepts a string.

/// <summary>
/// Sets the <c>HX-Reswap</c> header to specify how the response will be swapped.
/// </summary>
/// <param name="value">The header value to set.</param>
/// <returns>
/// The current <see cref="HtmxResponse"/> instance.
/// </returns>
public HtmxResponse Reswap(string value);

/// <summary>
/// Sets the <c>HX-Reswap</c> header to specify how the response will be swapped.
/// </summary>
/// <param name="value">The header value to set.</param>
/// <returns>
/// The current <see cref="HtmxResponse"/> instance.
/// </returns>
public HtmxResponse Reswap(HtmxSwap value);

And for the HtmxResponseAttribute, there is the ReswapExpression property.

/// <summary>
/// Gets or sets the <c>HX-Reswap</c> header that allows to specify how the response will be swapped.
/// </summary>
[MaybeNull]
public string ReswapExpression { get; set; }

/// <summary>
/// Gets or sets the <c>HX-Reswap</c> header that allows to specify how the response will be swapped.
/// </summary>
public HtmxSwap Reswap { get; set; }

allowing you to flexibly configure the swap header you need.

TagHelpers

The library provides 3 tag helpers:

• HtmxUrlTagHelper
• HtmxHeaderTagHelper
• HtmxConfigTagHelper

To make them available in your project, add the @addTagHelper directive in the Razor view.

@addTagHelper *, Ramstack.HtmxToolkit

To make the tag helpers available globally for the entire application, you should add this line to the _ViewImports.cshtml file, which is inherited by all view files by default.

HtmxUrlTagHelper

The HtmxUrlTagHelper allows generating links for HTMX methods similar to how it's done in ASP.NET Core for generating links, just replace the asp- prefix with the hx- prefix.

<div hx-target="this">
    <button hx-area="Sessions"
            hx-controller="Speaker"
            hx-action="Detail"
            hx-route-id="@Model.SpeakerId">Show Info</button>
</div>

The following code will be generated:

<div hx-target="this">
    <button hx-get="/Sessions/Speaker/Detail/1">Show Info</button>
</div>

By default, if no HTMX method is specified, hx-get is used. To specify a particular method, you can choose one from the following attributes: hx-get, hx-post, hx-put, hx-delete, or hx-patch.

For instance, in the following example, we use hx-post:

<div hx-target="this">
    <button hx-post
            hx-area="Sessions"
            hx-controller="Speaker"
            hx-action="Detail"
            hx-route-id="@Model.SpeakerId">Show Info</button>
</div>

In this case, the following code will be generated:

<div hx-target="this">
    <button hx-post="/Sessions/Speaker/Detail/1">Show Info</button>
</div>

The following attributes are also available for obtaining links to a page and a page handler:

<div hx-target="this">
    <button hx-page="/Attendee"
            hx-page-handler="Profile"
            hx-route-attendeeid="1">Attendee Profile</button>
</div>

The following code will be generated:

<div hx-target="this">
    <button hx-get="/Attendee?attendeeid=1&handler=Profile">Attendee Profile</button>
</div>

Also, the hx-all-route-data attribute is available, which accepts a dictionary where the key is the parameter name, and the value is the parameter value. In the example below, a dictionary with specific parameters is created, which is then used as the value of the hx-all-route-data attribute.

@{
    var parameters = new Dictionary<string, string> {
        { "category", "science" },
        { "pdf", "true" }
    };
}

<button hx-target="#result"
        hx-action="List"
        hx-all-route-data="parameters">Books</a>

The following code will be generated:

<button hx-target="#result" hx-get="/Books/List?category=science&pdf=true">Books</a>

In addition to the examples mentioned, the following properties are also available:

• hx-host
• hx-protocol
• hx-fragment

HtmxHeaderTagHelper

The htmx library allows adding custom headers that will be submitted with an AJAX request. However, since JSON format should be used for this, writing it out manually is not always convenient, especially considering the need to escape special characters. Fortunately, the library provides the HtmxHeaderTagHelper class, which takes care of this and allows specifying headers in a clearer and more readable format.

 <div hx-action="example"
      hx-header-Key-1="Value-1"
      hx-header-Key-2="Value-2">
      Get Some HTML, Including A Custom Header in the Request
  </div>

The following code will be generated:

 <div hx-get="/home/example"
      hx-headers='{"Key-1":"Value-1","Key-2":"Value-2"}'>
      Get Some HTML, Including A Custom Header in the Request
  </div>

Also, if you have a dictionary with the headers you need, you can assign them to the hx-all-headers attribute:

 <div hx-action="example"
      hx-all-headers="headers">
      Get Some HTML, Including A Custom Header in the Request
  </div>

The HtmxHeaderTagHelper will take care of all the remaining work regarding JSON serialization and escaping.

HtmxConfigTagHelper

As with hx-headers, configuring htmx settings requires a JSON representation. For working with configuration, the HtmxConfigTagHelper class is provided.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta htmx-config
          default-swap-style="HtmxSwap.OuterHtml"
          use-template-fragments="true"
          scroll-behavior="HtmxScrollBehavior.Smooth"
          include-antiforgery-token="true" />
</head>

The following code will be generated:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta name="htmx-config"
          content='{"defaultSwapStyle":"outerHTML","useTemplateFragments":true,"scrollBehavior":"smooth","antiForgery":{"headerName":"RequestVerificationToken","formFieldName":"__RequestVerificationToken","requestToken":"..."}}' />
</head>

Antiforgery Token

If you have enabled the generation of the Antiforgery token in the configuration (include-antiforgery-token="true"), then you need to include a small JavaScript file that will ensure this token is present in form parameters or headers and refresh it in a timely manner.

To do this, you can directly include the contents of the JavaScript file on the page:

<script>
  @Html.HtmxAntiforgeryScript()
</script>

Alternatively, to retrieve the debug version of the script, you can pass the debug parameter with a value of true:

<script>
  @Html.HtmxAntiforgeryScript(debug: true)
</script>

The debug parameter determines which version will be included. By default, the minimized version of the script will be returned, which weighs very little and takes up approximately 520 bytes.

The method returns a pre-initialized HtmlString with the script content, so there will be no unnecessary conversions and allocations every time it's used.

Alternatively, you can register the corresponding endpoint for the script by calling:

app.UseAuthorization();
...
app.MapHtmxAntiforgeryScript();
app.MapControllers();

By default, the registered path is mapped to /htmxtoolkit/[sha1-hash], where [sha1-hash] represents a precalculated hash of the script content. This approach eliminates the need to worry about cache invalidating when updating the script in the future as the hash automatically changes when the script content is modified.

If you want to change the path to your own, specify this path in the parameter.

app.MapHtmxAntiforgeryScript("/my-path");

Now, include it on the page.

<script src="@Html.HtmxAntiforgeryScriptPath()"></script>

Alternatively, to retrieve the debug version of the script, you can pass the debug parameter with a value of true, which instructs to include a query parameter ?debug in the path. The presence of this parameter determines the loading of the debug version:

<script src="@Html.HtmxAntiforgeryScriptPath(debug: true)"></script>

The debug parameter determines whether to load the minimized version (used by default) or the debug version of the script.

License

This package is released under the MIT License.