Replacement for @helper in ASP.NET Core

So far, i don't think ViewComponent solves that neither does TagHelper. Is there any replacement to this? Something that takes parameters and returns a HtmlString?

I don't see anything harmful with:

@helper foo(string something) {
     <div>Say @something</div>
}

var emailbody = classfilenameinAppCodefolder.foo("hello"); //store result in a variable for further processes

For now i believe its a temporary delete before RC. https://github.com/aspnet/Razor/issues/281 and https://github.com/aspnet/Mvc/issues/1130 Well! it better be. I hope someone is working on it. Without @helper, building large HtmlString or 'template' would be a serious pain.

Note: Partial View doesn't seem to do the trick. I think it only renders views not return view to variable.

Secondly, what happened to the App_Code folder?

According to the following Github issue, it looks like @helper is coming back and will be included in asp .net core 3.0.0 preview 4.

https://github.com/aspnet/AspNetCore/issues/5110

UPDATE

Starting in asp .net core 3, you can now define a local function within a Razor code block.

@{
    void RenderName(string name)
    {
        <p>Name: <strong>@name</strong></p>
    }

    RenderName("Mahatma Gandhi");
    RenderName("Martin Luther King, Jr.");
}

https://docs.microsoft.com/en-us/aspnet/core/mvc/views/razor?view=aspnetcore-3.1#razor-code-blocks

Alternatively you can use the @functions directive like this:

@{
    RenderName("Mahatma Gandhi");
    RenderName("Martin Luther King, Jr.");
}

@functions {
    private void RenderName(string name)
    {
        <p>Name: <strong>@name</strong></p>
    }
}

https://docs.microsoft.com/en-us/aspnet/core/mvc/views/razor?view=aspnetcore-3.1#functions

@{
    Func<String, IHtmlContent> foo = @<div>Say @item</div>;
}

I'd like to expand on @Alexaku's answer and show how I've implemented a helper like function. It's only useful on one specific page but it allows you to execute a piece of razor code multiple times with input parameters. The syntax is not great but I've found it very useful in the absence of razor's @helper function. First declare some kind of Dto that will contain the input parameters into the function.

@functions {
   private class Dto
   {
      public string Data { get;set; }
   }
}

Then declare the razor function. Note that the displayItem value can be multi-line and also note that you access the Dto variable using the @item.

@{
   Func<Dto, IHtmlContent> displayItem = @<span>@item.Data</span>;
}

Then when you want to use the razor template you can call it like the following from anywhere in the page.

<div>
   @displayItem(new Dto {Data = "testingData1" });
</div>
<div>
   @displayItem(new Dto {Data = "testingData2" });
</div>

For .NET Core 3, you can use local functions:

@{
    void RenderName(string name)
    {
        <p>Name: <strong>@name</strong></p>
    }

    RenderName("Mahatma Gandhi");
    RenderName("Martin Luther King, Jr.");
}

https://docs.microsoft.com/en-us/aspnet/core/mvc/views/razor?view=aspnetcore-3.1#razor-code-blocks

Replacement for @helper in ASP.NET Core

Related

Recent Posts