CSharp Client

FlexSearch comes with a C# client that is automatically generated from the Swagger definition. You can find the C# client dll in the FlexSearch.Clients.*.zip package under the name:


All you need to do to start using it is to reference this DLL in your project.


The C# client is split into three parts / namespaces:

  1. Model
    Contains all of the requests, responses, enums and helper models that you will need for working with the out-of-box FlexSearch functionality.
  2. Api
    Contains all of the necessary methods for accessing FlexSearch HTTP endpoints. The APIs are grouped by Swagger tags into:
    • Indices API - has methods for working with Indices: create, update, delete, check, etc.
    • Search API
    • Documents API
    • Analyzer API
    • Common API - has methods for working with the most populat FlexSearch endpoints such as creating an index, searching, getting documents, as well as accessing the FlexSearch connectors.
    • Jobs API
    • Server API - has methods for setting up a demo index, getting server stats, ping-ing, etc.
  3. Client
    Contains the code that handles the HTTP calls. The Client is used by the Api's during instantiation. It can be instantiated by using either a base path (e.g. http://localhost:9800) or an HttpMessageHandler.

Request Model

All FlexSearch Request objects derive from IDataTransferObject. This forces the users to implement a validation method for each request type. The method (Validate()) will be called by FlexSearch at the beginning of any HTTP handler.

Guidelines on implementing your own FlexSearch Request

Implementing the Validate() Method

The Validate() method should populate the IDataTransferObject fields in the following way:

  • Validated - should be used to indicate if the Validate() method has been called at least once.
  • ErrorField - should hold the name of the Field that was identified as having a problem.
  • ErrorDescription - should contain an explanation of the problem.

Using DataContract and DataMember attributes

In order to make your request fully compatible with FlexSearch, you should use:

  • System.Runtime.Serialization.DataContract attribute on your request
  • System.Runtime.Serialization.DataMember attribute on the properties you want to expose. Typically, these would be the new properties you create, not the ones implemented from IDataTransferObject.

Using JsonProperty and JsonIgnore attributes

We suggest using the JsonIgnore attribute on the properties implemented from IDataTransferObject.
The JsonProperty attribute should be used on the new properties you’ve created, being careful to use camelCase for the PropertyName.

Response Model

All FlexSearch Responses have two Properties:

  • Data - this contains the actual data that you want to retrieve when making a request

    E.g. The ID of the newly created Index or the list of Analyzer DTOs when you’re getting all Analyzers

  • Error - In case there was an error when running the request, this property will be populated. It contains helpful information to help you identify what the problem is.

    These are the pieces of information present in the Error property:

    1. Message - It contains a human readable description of the error
    2. OperationCode - It contains a code that identifies the category of the error
    3. Properties - This is a list of the key pieces of data that concern this error.


        "message": "Document ID '333' not found on index 'contact'",
        "operationCode": "DocumentIdNotFound",
        "properties": {
            "indexName": "contact",
            "id": "333"

Guidelines on implementing your own Response

When implementing your own response you don’t need to worry about the Data and Error part. FlexSearch will handle that for you.

You will just need to focus on annotating your object with the attributes DataContract, DataMember and JsonProperty, like instructed in the Request Model.

Usage example

In this example I’m going to do a search for any of the words “most”, “prosperous” and “countries” inside the field background of the country index.

    // First initialize a client to connect to our FlexSearch URL
    var searchApi = new SearchApi("http://localhost:9800")

    // Next create the request that we want to send. In this case, the
    // request is of type `SearchQuery`
    var query = new SearchQuery("country", "anyOf(background, 'most prosperous countries')");

    // We want to get back the fields "countryname" and "background"      
    query.Columns = new string[] { "countryname"; "background" };

    // Now we submit the request using a POST
    var response = api.Search(query, query.IndexName);

    // We interpret the response
    if (response.Error?.Message != null)
        Console.WriteLine($"Got an error: {response.Error.Message}");
        Console.WriteLine($"Got back {response.Data.RecordsReturned} records");