How can I do a string comparison in a Handlebars.Net template?

Question

I am trying to use a Handlebars.Net template to iterate over a list of string and to render either one thing or the other based on the value of the string.

This is a cut-down example of what I am trying to achieve. I have an object with a list of string property, and a template that loops through the list and renders some HTML based on the value of the string:

Simple object with list:

public class Box
{
   public List<string> BoxItems { get; set; }
}

Simple template to iterate over the list and render one thing or the other:

{{#each Box.BoxItems }}
    {{#if this == "item" }}
        <p>This is a box item</p>
    {{else}}
        <p>This is not a box item</p>
    {{/if}}
{{/each}}

I have tried registering my own helper but haven't managed to make this work.

How can I can get this to work using the Handlebars.Net port (not the HandlebarsJS version)?

EDIT:

The helper I tried using that doesn't work is this:

handlebars.RegisterHelper("eq_test", (a, b) => a.ToString().Equals(b.ToString()));

and it is used in the template like this:

{{#each Box.BoxItems }}
    {{#if (eq_test this "item") }}
        <p>This is a box item</p>
    {{else}}
        <p>This is not a box item</p>
    {{/if}}
{{/each}}

Serigan · Accepted Answer · 2022-09-07 11:54:18Z

4

Answering my own question,

I registered the helper like this:

handlebars.RegisterHelper("isEq", (ctx, args) => {
    if (args.Length != 2)
    {
       throw new ArgumentOutOfRangeException();
    }
    
    string str1 = args[0].ToString();
    string str2 = args[1].ToString();

    return str1 == str2;
});

And then I used it in the template like this:

{{#each Box.BoxItems }}
   {{#if (isEq this item) }}
      <p>This is a box item</p>
   {{else}}
      <p>This is not a box item</p>
   {{/if}}
{{/each}}

Obviously this is not a perfect example of how to do this. There is no real checking done on the parameters and it is clearly a string comparison.

But hopefully it will save somebody a few hours of figuring out how to register a simple equality check helper for Handlebars.Net.

answered Sep 7, 2022 at 11:54

Serigan

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1 Comment

Felix Arnold Over a year ago

you may want to see this post: stackoverflow.com/questions/59269178/…

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