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var Res : integer;
var NetClient := System.Net.HttpClient.THTTPClient.Create;
try
  NetClient.ProtocolVersion := THTTPProtocolVersion.HTTP_2_0;
  var Response := NetClient.Get('https://www.google.com');
  if Response.StatusCode = 200 then begin
    case Response.Version of
      THTTPProtocolVersion.UNKNOWN_HTTP: Res := 0;
      THTTPProtocolVersion.HTTP_1_0: Res := 1;
      THTTPProtocolVersion.HTTP_1_1: Res := 2;
      THTTPProtocolVersion.HTTP_2_0: Res := 3;
    end; {case}
  end; {if}
finally
  NetClient.Free;
end; {try .. finally}