RestSharp write api interface test and implement asynchronous call (no lag)

First, make sure you have the RestSharp NuGet package installed. If it is not installed, you can install it with the following command:

Install-Package RestSharp

Then, in your C# code, you can follow these steps:

1. References the RestSharp namespace.
2. Create a RestClient instance.
3. Create a RestRequest instance and set the request method and URL.
4. Performs an asynchronous POST request.
5. Processing Response.

The following is sample code:

using System;
using ;
using RestSharp;

public class RestClientExample
{
    private readonly RestClient _client;

    public RestClientExample(string baseUrl)
    {
        _client = new RestClient(baseUrl);
    }

    public async Task<RestResponse> GetAreaAsync()
    {
        var request = new RestRequest("GetArea", );
        
        // If you need to add a request header or request body, you can do so here
// ("Authorization", "Bearer your-token");
        // ("key", "value");

        var response = await _client.ExecutePostAsync(request);
        return response;
    }
}

// Example of use
class Program
{
    static async Task Main(string[] args)
    {
        var baseUrl = "/api"; // Replace with your API base URL
var restClient = new RestClientExample(baseUrl);

        try
        {
            var response = await ();
            
            if ()
            {
                ($"Request successful, response content:{}");
            }
            else
            {
                ($"Request failed, status code:{}, error message:{}");
            }
        }
        catch (Exception ex)
        {
            (An exception occurred in "$":{}");
        }
    }
}

Please note that you will need to replacebaseUrlvariable's value and add the necessary request headers and parameters as required by the API. If the API requires authentication, make sure to add the appropriate authorization headers.

In addition, if your API returns data in JSON format, you can use theto get the raw response content and then use a JSON parsing library (e.g.) to parse the data.