This preview of .NET 7 includes improvements to type converters, JSON contract customization, System.Formats.Tar API updates, constraints to .NET template authoring, and performance enhancements in the CodeGen area. 

MockHttp is a testing layer for Microsoft's HttpClient library. It allows stubbed responses to be configured for matched HTTP requests and can be used to test your application's service layer. 

var mockHttp = new MockHttpMessageHandler();

// Setup a respond for the user api (including a wildcard in the URL)
mockHttp.When("http://localhost/api/user/*")
        .Respond("application/json", "{'name' : 'Test McGee'}"); // Respond with JSON

// Inject the handler or client into your application code
var client = mockHttp.ToHttpClient();

var response = await client.GetAsync("http://localhost/api/user/1234");
// or without async: var response = client.GetAsync("http://localhost/api/user/1234").Result;

var json = await response.Content.ReadAsStringAsync();

// No network connection required
Console.Write(json); // {'name' : 'Test McGee'}

{
    "manufacturer": "Samsung",
    "market_name": "Galaxy Note10+ 5G",
    "codename": "d2x",
    "model": "SM-N976B"
  }

It includes a new Json serializer, support for publishing single file executables, an update to runtime roll-forward, and changes in the BCL. 

Tabulator: A Fully Featured, Interactive Table JavaScript Library — Create interactive data tables quickly from any HTML table or JavaScript or JSON data source. 

ASP.NET Core 2.1

[HttpPost]
public async Task<JsonResult> GetProducts([FromBody]Request request)
{
    var context = GetContext();

    var result = await context.Products.ToDataSourceAsync(request);

    return Json(result);
}