imprimir.cs

var client = new RestClient("http://localhost:8000/imprimir");
client.Timeout = -1;
var request = new RestRequest(Method.POST);
request.AddHeader("Content-Type", "application/json");
var body = @"{
" + "\n" +
@"    ""operaciones"": [
" + "\n" +
@"        {
" + "\n" +
@"            ""nombre"": ""Operación que no existe"",
" + "\n" +
@"            ""argumentos"": []
" + "\n" +
@"        },
" + "\n" +
@"        {
" + "\n" +
@"            ""nombre"": ""EstablecerAlineacion"",
" + "\n" +
@"            ""argumentos"": [
" + "\n" +
@"                1
" + "\n" +
@"            ]
" + "\n" +
@"        },
" + "\n" +
@"        {
" + "\n" +
@"            ""nombre"": ""EscribirTexto"",
" + "\n" +
@"            ""argumentos"": [
" + "\n" +
@"                ""Hola mundo desde Postman!\nUn barcode:\n""
" + "\n" +
@"            ]
" + "\n" +
@"        },
" + "\n" +
@"        {
" + "\n" +
@"            ""nombre"": ""ImprimirCodigoDeBarrasCode39"",
" + "\n" +
@"            ""argumentos"": [
" + "\n" +
@"                ""123"",
" + "\n" +
@"                true,
" + "\n" +
@"                true,
" + "\n" +
@"                100,
" + "\n" +
@"                320,
" + "\n" +
@"                0
" + "\n" +
@"            ]
" + "\n" +
@"        },
" + "\n" +
@"        {
" + "\n" +
@"            ""nombre"": ""Iniciar"",
" + "\n" +
@"            ""argumentos"": []
" + "\n" +
@"        },
" + "\n" +
@"        {
" + "\n" +
@"            ""nombre"": ""Feed"",
" + "\n" +
@"            ""argumentos"": [
" + "\n" +
@"                2
" + "\n" +
@"            ]
" + "\n" +
@"        }
" + "\n" +
@"    ],
" + "\n" +
@"    ""nombreImpresora"": ""PT210"",
" + "\n" +
@"    ""serial"": """"
" + "\n" +
@"}";
request.AddParameter("application/json", body,  ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
Console.WriteLine(response.Content);