Azure Cognitive Search from .NET Core and C#

The Azure Cognitive Search engine is the search of choice in the Microsoft Azure. The search engine can be used in a myriad of ways and there are so many options that it can be difficult to find a starting point.

To help myself, I made this simple class that implements one of the simplest setups and a great starting point for more advanced searches.

The class is an example on how to do a free text search in one index.

THE NUGET REFERENCES: 

The code references the following packages:

• Azure.Search.Documents

STEP 1: DEFINE A MODEL CLASS FOR THE INDEX

You must define a model class that matches the fields you wish to have returned from the index. This is my sample index called “advert”:

Sample Advert Index

And I have defined the fields relevant for my search result:

public class Advert
{
  public string Id { get; set; }
  public string Title { get; set; }
  public string Description { get; set; }
}

STEP 2: THE SAMPLE SEARCH CLASS:

This is just an example search class that implement the most basic functions. You need to specify your own URL to the search engine and the proper API key.

using Azure;
using Azure.Search.Documents;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace MyCode
{
  public class AzureSearch
  {
    public async Task<IEnumerable<string>> Search(string query)
    {
      SearchClient searchClient = CreateSearchClientForQueries("advert");
      SearchOptions options = new SearchOptions() { IncludeTotalCount = true };
      var results = await searchClient.SearchAsync<Advert>(query, options);

      List<string> documents = new List<string>();
      Console.WriteLine(results.Value.TotalCount);
      foreach (var s in results.Value.GetResults())
      {
        documents.Add(s.Document.Title);
      }
      return documents;
    }

    private static SearchClient CreateSearchClientForQueries(string indexName)
    {
      string searchServiceEndPoint = "https://mysearch.windows.net";
      string queryApiKey = "the api key";

      SearchClient searchClient = new SearchClient(new Uri(searchServiceEndPoint), indexName, new AzureKeyCredential(queryApiKey));
      return searchClient;
    }
  }
}

STEP 3: THE USAGE

Remember that the code above is just a sample on how to do a basic free-text search.

class Program
{
  static void Main(string[] args)
  {
    var result = new AzureSearch().Search("BrianCaos").Result;
    foreach (var r in result)
      Console.WriteLine(r);
  }
}

MORE ADVANCED SEARCHES:

To do more advanced searches, you usually modify the SearchOptions. For example, if you wish to apply a filter to the search, you can use the “Filter” property. This property takes a slightly different format, as “=” is written “eq”, “>” is “gt” and “<” is “lt”.

public async Task<IEnumerable<string>> Search(string query)
{
  SearchClient searchClient = CreateSearchClientForQueries("advert");
  SearchOptions options = new SearchOptions() 
  { 
    IncludeTotalCount = true, 
    Filter = "MyField eq true" 
  };
  var results = await searchClient.SearchAsync<Advert>(query, options);

  List<string> documents = new List<string>();
  Console.WriteLine(results.Value.TotalCount);
  foreach (var s in results.Value.GetResults())
  {
    documents.Add(s.Document.Title);
  }
  return documents;
}

PAGINATION:

To do pages searches, you use the SearchOptions again. Use the “Size” and “Skip” parameters to specify paging. “Size” determines the number of results, “Skip” determines how many results to skip before returning results. This example implements a 1-based paging:

public async Task<IEnumerable<string>> Search(string query, int page, int pageSize)
{
  SearchClient searchClient = CreateSearchClientForQueries("advert");
  SearchOptions options = new SearchOptions() 
  { 
    IncludeTotalCount = true, 
    Size = pageSize,
    Skip = (page-1)*pageSize
  };
  var results = await searchClient.SearchAsync<Advert>(query, options);

  List<string> documents = new List<string>();
  Console.WriteLine(results.Value.TotalCount);
  foreach (var s in results.Value.GetResults())
  {
    documents.Add(s.Document.Title);
  }
  return documents;
}

MORE TO READ:

• Azure Cognitive Search from Microsoft
• How to use Azure.Search.Documents in a C# .NET Application from Microsoft
• Programmatically create and delete Azure Cognitive Search Indexes from C# code from briancaos
• Search Documents (Azure Cognitive Search REST API) from Microsoft