best practice to render optional links

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Jeroen Oostwouder 100 posts 296 karma points

Jun 17, 2022 @ 09:35
0

Best practice to render optional links
I'm wondering what is best practice, when you have to deal with optional links/containers in html.

For example: I have a list of elements. Each element has an image field, and a Url-picker field. The Url-picker value is optional.

So I loop through the elements, to render the html like this:
```
foreach (var element in elements) {
    <a href="@element.Link.Url"><img src="@element.Image.Url()"></a>
}
```
How can I make the anchor optional?

I can't do:
```
foreach (var element in elements) {
    if (element.Link != null) {
        <a href="@element.Link.Url">
    }
    <img src="@element.Image.Url()">
    if (element.Link != null) {
        </a>
    }
}
```
Because then I open an -tag without closing in the same block.

In Umbraco7 I did this:
```
foreach (var element in elements) {
    @Umbraco.If(element.Link != null, "<a href=\"" + element.Link.Url + "\">")
    <img src="@element.Image.Url()">
    @Umbraco.If(element.Link != null, "</a>")
}
```
But the UmbracoHelper doesn't seem to have an 'if' function anymore.

What's the best solution for this problem?
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Marc Goodson 2155 posts 14408 karma points MVP 9x c-trib

Jun 20, 2022 @ 10:19
100
Hi Jeroen

Number of ways you could look at this...

You could create a razor helper to write out the image bit eg
```
@{
void DisplayLovelyImage(IPublishedContent image, string altText){
<img src="@image.Url" alt="@altText" />
}
}
```
and then in your foreach have:
```
@if (element.Link != null)
{
   <a href="@element.Link.Url">
    @{ DisplayLovelyImage(element.Image, element.Image.Name); }
  </a>
}
else
{
  @{ DisplayLovelyImage(element.Image, element.Image.Name); }
}
```
It's also not a bad idea to have a ViewComponent responsible for rendering all your img / picture tags from your razor, so 'one place' to update the logic around the displaying of images in a consistent way, eg if you want to provide responsive srcsets etc - then your DisplayLovelyImage method would be:
```
@await Component.InvokeAsync("DisplayLovelyImage", new { image = element.Image, width = 900, height = 0, cssClassName = "scale" })
```
regards

Marc
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Jeroen Oostwouder 100 posts 296 karma points

Jun 21, 2022 @ 07:45

0

That's a nice way indeed. I'm still not too familiar with components, but I might give that a try too.

Thank you.

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Marc Goodson 2155 posts 14408 karma points MVP 9x c-trib

Jun 21, 2022 @ 07:54

Hi Jeroen

This is a good intro: https://docs.microsoft.com/en-us/aspnet/core/mvc/views/view-components?view=aspnetcore-6.0#add-a-viewcomponent-class

With ViewComponents, there are two parts, the 'code' and the 'view'

You create a class that inherits from ViewComponent, so for example, we tend to use Slimsy a lot on sites, and so this ViewComponent builds up different variations of the Url, low quality image etc for lazyish loading

public class ResponsiveImageViewComponent : ViewComponent
    {   
            public async Task<IViewComponentResult> InvokeAsync(MediaWithCrops image, UrlHelper urlHelper, int width, int height, string cssClassName = "")
            {
                var imageModel = new ResponsiveImageViewModel();

                if (image != null)
                {
                    string defaultMimeType;
                    var umbracoExtension = image.Value<string>(Constants.Conventions.Media.Extension);
                    var defaultFormat = umbracoExtension;

                    switch (umbracoExtension)
                    {
                        case "jpg":
                            defaultMimeType = "image/jpeg";
                            break;
                        case "png":
                            defaultMimeType = "image/png";
                            break;
                        case "gif":
                            defaultMimeType = "image/gif";
                            break;
                        default:
                            defaultMimeType = "image/jpeg";
                            defaultFormat = "jpg";
                            break;
                    }

                    var lqipWidth = (int)Math.Round((decimal)width / 2);
                    var lqipHeight = (int)Math.Round((decimal)height / 2);

                    var imgSrcSet = urlHelper.GetSrcSetUrls(image, width, height, outputFormat: defaultFormat);
                    var imgSrc = SlimsyExtensions.GetCropUrl(image, width, height, furtherOptions: "&format=" + defaultFormat);

                    // ** Using half width/height for LQIP to reduce filesize to a minimum, CSS must oversize the images **
                    var imgLqip = SlimsyExtensions.GetCropUrl(image, lqipWidth, lqipHeight, quality: 20, furtherOptions: "&format=" + defaultFormat);

                    //Image Model Stuff
                    imageModel.DefaultSrcSetUrl = imgSrcSet;
                    imageModel.Id = image.Id;
                    imageModel.Url = imgSrc;
                    imageModel.CssClass = cssClassName;
                    imageModel.LqipUrl = imgLqip;
                    imageModel.AltText = image.Name;
                }


                return View("ResponsiveImage", imageModel);
            }
        }

Then you create a corresponding View in /Views/Components/ResponsiveImage/ResponsiveImage.cshtml

Which would then write out the img tag

@model ResponsiveImageViewModel
@{
    if (Model != null)
    {
        var cssClass = "lazyload";
        if (!string.IsNullOrEmpty(Model.CssClass))
        {
            cssClass += $" {Model.CssClass}";
        }


        <picture>
            <!--[if IE 9]><video style="display: none"><![endif]-->
            <source data-srcset="@Model.DefaultSrcSetUrl" srcset="@Model.LqipUrl" type="@Model.MimeType" data-sizes="auto" />
            <!--[if IE 9]></video><![endif]-->
            <img src="@Model.LqipUrl"
                 data-src="@Model.Url"
                 class="@cssClass"
                 data-sizes="auto"
                 alt="@Model.AltText" />
        </picture>
    }
}

if that gives you the idea!

regards

marc

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