Keynotes for Solr Index in Sitecore 9

I've recently implemented a product list page and -as you can guess- I've needed to configure a custom index for my products. I will share some keynotes about that, I believe they might be useful for anyone who needs a similar thing.

How to configure a custom index in Solr?
Luckily, we already have a good article which shows how to create custom Solr indexes in Sitecore 9. I followed the steps and created my product indexes (my Sitecore version is 9.0.1).

I added necessary fields and templates to my config file:

                <!-- Included fields -->
                <include hint="list:AddIncludedField">
                  <Name>{A00DA813-46FF-47E4-ADD7-75C1333ACF32}</Name>
                  <CommercialShortText>{0AFE5D2A-8172-46BA-BD96-FD6838E3D65B}</CommercialShortText>
                  <TitleProductPage>{E7E6F859-F989-4BA3-8F31-7A03C9BD69E4}</TitleProductPage>
                  <ProductDescription>{14EC7D7E-D6ED-4F95-936B-6988F49A8D9B}</ProductDescription>
                </ProductClasses>
                </include>

                <!-- Included templates -->
                <include hint="list:AddIncludedTemplate">
                  <Product>{032168C8-4E59-485A-8FBC-0E587AB41EA6}</Product>
                </include>

However, it was not enough for my case, I needed to add product image field as well.

If you add an Image field to index like other text fields above, it only returns "alt" information of image. You don't get image url or any other details.

You can see why it returns alt info by checking default Solr config file:

ImageFieldRenderer is responsible class for image field type and it is implemented to return alt tag:

What should we do then?

Computed index field.

How to add a computed index field?

It should be added under "raw:AddComputedIndexField" key.

                <fields hint="raw:AddComputedIndexField">
                  <field fieldName="product_image_url" returnType="string">Namespace.ProductImageComputedIndexField, DLL</field>
                </fields>

And your class will look like this:

public class ProductImageComputedIndexField : AbstractComputedIndexField
    {
        public override object ComputeFieldValue(IIndexable indexable)
        {
            var item = (Item)(indexable as SitecoreIndexableItem);

            if (item == null)
                return null;

            if (!item.TemplateID.Equals(IProductConstants.TemplateId)) return null;

            var imageField = (ImageField)item.Fields[IProductConstants.Product_ImageFieldName];

            if (imageField?.MediaItem == null) return null;

            using (new SecurityDisabler())
            {
                using (new SiteContextSwitcher(Factory.GetSite("website")))
                {
                    var uri = MediaManager.GetMediaUrl(imageField.MediaItem, new MediaUrlOptions { UseItemPath = true });

                    return uri;
                }
            }
        }

You think you configured everything correctly but it still doesn't work somehow. Maybe you forgot something and then, you need to check your indexed results.

How to check your indexed items?
There are several options but I will show the basic one: Use Solr panel!

Open your solr; most probably, it works here.

Select your custom index from core selector dropdown, click query and then execute:

You can see the fields are in index and check the results are as expected or not. If not, you can reindex from Sitecore panel or check your code if something configured wrong.

How to create custom SearchResultItem?
After you add fields to config file, they will be added to index. But how will you get those in code?
To do that, you will need to create your own search result class and bind your fields like example below:

public class SearchProductResultItem : SearchResultItem
    {
        [DataMember]
        [IndexField("name")]
        public string ProductName { get; set; }

        [DataMember]
        [IndexField("product_description")]
        public string ProductDescription { get; set; }


        [DataMember]
        [IndexField("product_image_url")]
        public string ProductImageUrl { get; set; }

    }

Then, you can use in query:

using (var context = Index.CreateSearchContext())
{
                    var filter = context.GetQueryable<SearchProductResultItem>()
                        .Filter(x => x.TemplateId == IProductConstants.TemplateId &&
                                   x.Language == Context.Language.Name)
                        .OrderBy(x => x.Name)
                        .Skip(pageInfo.SkipIndex)
                        .Take(pageInfo.PageSize)
                        .ToList();

Hope, it helps!