Package | Version |
---|---|
Handlebars.CSharp | |
Handlebars.Extension.CompileFast | |
Handlebars.Extension.Logging |
This is a fork of rexm/Handlebars.Net developed by @rexm. Unfortunately project had no activity for a while. I'd be glad to back-merge all the changes back to original repo if I'd have a chance. Meanwhile I'd try to support the fork.
Blistering-fast Handlebars.js templates in your .NET application.
Handlebars.js is an extension to the Mustache templating language created by Chris Wanstrath. Handlebars.js and Mustache are both logicless templating languages that keep the view and the code separated like we all know they should be.
Check out the handlebars.js documentation for how to write Handlebars templates.
handlebars.csharp doesn't use a scripting engine to run a Javascript library - it compiles Handlebars templates directly to IL bytecode. It also mimics the JS library's API as closely as possible.
Install
dotnet add package Handlebars.CSharp
Extensions
dotnet add package Handlebars.Extension.CompileFast
dotnet add package Handlebars.Extension.Logging
Usage
string source =
@"<div class=""entry"">
<h1>{{title}}</h1>
<div class=""body"">
{{body}}
</div>
</div>";
var template = Handlebars.Compile(source);
var data = new {
title = "My new post",
body = "This is my first post!"
};
var result = template(data);
/* Would render:
<div class="entry">
<h1>My New Post</h1>
<div class="body">
This is my first post!
</div>
</div>
*/
Registering Partials
string source =
@"<h2>Names</h2>
{{#names}}
{{> user}}
{{/names}}";
string partialSource =
@"<strong>{{name}}</strong>";
Handlebars.RegisterTemplate("user", partialSource);
var template = Handlebars.Compile(source);
var data = new {
names = new [] {
new {
name = "Karen"
},
new {
name = "Jon"
}
}
};
var result = template(data);
/* Would render:
<h2>Names</h2>
<strong>Karen</strong>
<strong>Jon</strong>
*/
Registering Helpers
Handlebars.RegisterHelper("link_to", (writer, context, parameters) => {
writer.WriteSafeString("<a href='" + context.url + "'>" + context.text + "</a>");
});
string source = @"Click here: {{link_to}}";
var template = Handlebars.Compile(source);
var data = new {
url = "https://github.com/rexm/handlebars.net",
text = "Handlebars.Net"
};
var result = template(data);
/* Would render:
Click here: <a href='https://github.com/rexm/handlebars.net'>Handlebars.Net</a>
*/
This will expect your views to be in the /Views folder like so:
Views\layout.hbs |<--shared as in \Views
Views\partials\somepartial.hbs <--shared as in \Views\partials
Views\{Controller}\{Action}.hbs
Views\{Controller}\{Action}\partials\somepartial.hbs
Registering Block Helpers
HandlebarsBlockHelper _stringEqualityBlockHelper = (TextWriter output, HelperOptions options, dynamic context, object[] arguments) => {
if (arguments.Length != 2)
{
throw new HandlebarsException("{{StringEqualityBlockHelper}} helper must have exactly two argument");
}
string left = arguments[0] as string;
string right = arguments[1] as string;
if (left == right)
{
options.Template(output, null);
}
else
{
options.Inverse(output, null);
}
};
Handlebars.RegisterHelper("StringEqualityBlockHelper", _stringEqualityBlockHelper);
Dictionary<string, string> animals = new Dictionary<string, string>() {
{"Fluffy", "cat" },
{"Fido", "dog" },
{"Chewy", "hamster" }
};
string template = "{{#each @value}}The animal, {{@key}}, {{StringEqualityBlockHelper @value 'dog'}}is a dog{{else}}is not a dog{{/StringEqualityBlockHelper}}.\r\n{{/each}}";
Func<object, string> compiledTemplate = Handlebars.Compile(template);
string templateOutput = compiledTemplate(animals);
/* Would render
The animal, Fluffy, is not a dog.
The animal, Fido, is a dog.
The animal, Chewy, is not a dog.
*/
Performance
Compilation
Compared to rendering, compiling is a fairly intensive process. While both are still measured in millseconds, compilation accounts for the most of that time by far. So, it is generally ideal to compile once and cache the resulting function to be re-used for the life of your process.
Rendering
Nearly all time spent in rendering is in the routine that resolves values against the model. Different types of objects have different performance characteristics when used as models.
Model Types
- The absolute fastest model is a
IDictionary<string, object>
(microseconds). - The next fastest is a POCO (typically a few milliseconds for an average-sized template and model), which uses traditional reflection and is fairly fast.
- Rendering starts to get slower (into the tens of milliseconds or more) on dynamic objects.
- The slowest (up to hundreds of milliseconds or worse) tend to be objects with custom type implementations (such as
ICustomTypeDescriptor
) that are not optimized for heavy reflection.
A frequent performance issue that comes up is JSON.NET's JObject
, which for reasons we haven't fully researched, has very slow reflection characteristics when used as a model in Handlebars.Net. A simple fix is to just use JSON.NET's built-in ability to deserialize a JSON string to an ExpandoObject
instead of a JObject
. This will yield nearly an order of magnitude improvement in render times on average.
More
For mo retails see Performance measurements
Future roadmap
TBD
Contributing
Pull requests are welcome! The guidelines are pretty straightforward:
- Only add capabilities that are already in the Mustache / Handlebars specs
- Avoid dependencies outside of the .NET BCL
- Maintain cross-platform compatibility (.NET/Mono; Windows/OSX/Linux/etc)
- Follow the established code format