Code accompanying post at https://blog.yannickreekmans.be/index-your-ghost-blog-in-azure-search-with-an-azure-function/

function.proj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
    <AzureFunctionsVersion>v2</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Search" Version="5.0.2" />
    <PackageReference Include="morelinq" Version="3.0.0" />
  </ItemGroup>
</Project>

run.csx

#r "Newtonsoft.Json"
#r "Microsoft.WindowsAzure.Storage"

using System.Net;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Primitives;
using Newtonsoft.Json;
using Microsoft.WindowsAzure.Storage.Blob;
using Microsoft.Azure.Search;
using Microsoft.Azure.Search.Models;
using MoreLinq.Extensions;

private static HttpClient client;

private static readonly string BlogUrl = "";
private static readonly string ContentApiKey = "";
private static readonly string SearchServiceName = "";
private static readonly string SearchAdminApiKey = "";

public static async Task<IActionResult> Run(HttpRequest req, ILogger log)
{
    log.LogInformation("Loading posts from blog");
    var client = GetClient();
    var response = await client.GetAsync($"{BlogUrl}/ghost/api/v2/content/posts/?include=tags,authors&formats=plaintext&limit=15&key={ContentApiKey}");
    var json = await response.Content.ReadAsStringAsync();
    dynamic data = JsonConvert.DeserializeObject(json);
    List<dynamic> postList = data.posts.ToObject<List<dynamic>>();

    log.LogInformation("Converting posts into the correct format");
    var postsArray = postList.ConvertAll((p) => {
        List<dynamic> tags = p.tags.ToObject<List<dynamic>>();
        return new Post() {
            Id = p.id,
            Uuid = p.uuid,
            Title = p.title,
            Slug = p.slug,
            PlainText = p.plaintext,
            FeatureImage = p.feature_image,
            CustomExcerpt = p.custom_excerpt,
            Page = p.page,
            Url = p.url,
            CreatedAt = p.created_at,
            UpdatedAt = p.updated_at,
            PublishedAt = p.published_at,
            Tags = tags.Select(t => t.slug.ToString()).Cast<string>().ToArray()
        };
    });

    log.LogInformation("Creating search service client");
    var searchClient = new SearchServiceClient(SearchServiceName, new SearchCredentials(SearchAdminApiKey));
    
    log.LogInformation("Deleting Index");
    await searchClient.Indexes.DeleteAsync("posts");

    log.LogInformation("Creating Index");
    var definition = new Index()
    {
        Name = "posts",
        Fields = FieldBuilder.BuildForType<Post>(),
        CorsOptions = new CorsOptions()
        {
            AllowedOrigins = new List<string>() { BlogUrl },
            MaxAgeInSeconds = 300
        }
    };
    await searchClient.Indexes.CreateAsync(definition);

    log.LogInformation("BatchInsert Posts into Index");
    var indexClient = searchClient.Indexes.GetClient("posts");
    foreach(var objectBatch in postsArray.Batch(1000))
    {
        try
        {
            IndexBatch<Post> batch = IndexBatch.MergeOrUpload(objectBatch);
            await indexClient.Documents.IndexAsync(batch);
        }
        catch (IndexBatchException e)
        {
            log.LogError(e, $"Failed to index some of the groups: {string.Join(", ", e.IndexingResults.Where(r => !r.Succeeded).Select(r => r.Key))}");
        }
    }

    return(ActionResult)new OkResult();
}

private static HttpClient GetClient()
{
    client = client ?? new HttpClient();
    return client;
}

[SerializePropertyNamesAsCamelCase]
public class Post
{
    [System.ComponentModel.DataAnnotations.Key]
    [IsRetrievable(true)]
    public string Id { get; set; }

    [IsSearchable, IsRetrievable(true)]
    public string Uuid { get; set; }

    [IsSearchable, IsRetrievable(true)]
    public string Title { get; set; }

    [IsSearchable, IsRetrievable(true)]
    public string Slug { get; set; }
    
    [IsSearchable, IsRetrievable(true)]
    public string PlainText { get; set; }

    [IsSearchable, IsRetrievable(true)]
    public string FeatureImage { get; set; }

    [IsSearchable, IsRetrievable(true)]
    public string CustomExcerpt { get; set; }

    [IsSearchable, IsRetrievable(true)]
    public string[] Tags { get; set; }

    [IsRetrievable(true)]
    public string Url { get; set; }

    [IsFilterable, IsRetrievable(true)]
    public bool? Page { get; set; }

    [IsRetrievable(true)]
    public DateTime? CreatedAt { get; set; }
    
    [IsRetrievable(true)]
    public DateTime? UpdatedAt { get; set; }
    
    [IsRetrievable(true)]
    public DateTime? PublishedAt { get; set; }
}

Updated the function script to use the newer Azure.Cognitive.Search client V11, which replaces the above V10 Azure.Search client
https://gist.github.com/SimonDarksideJ/6c4099900f1c66383a2ac00a1a322dfe