Implementação Pix Efi em .NET Framework

global.asax

'precisa adicionar o webapi para poder receber o post no Webhook
Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
        System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls12
        RouteTable.Routes.MapHttpRoute("DefaultApi", "api/{controller}/{action}/{id}", New With {Key .id = System.Web.Http.RouteParameter.[Optional]
})
        GlobalConfiguration.Configuration.Formatters.Clear()
        GlobalConfiguration.Configuration.Formatters.Add(New JsonMediaTypeFormatter With {
            .SerializerSettings = New JsonSerializerSettings With {
                .Formatting = Formatting.None,
                .DateFormatHandling = DateFormatHandling.IsoDateFormat,
                .NullValueHandling = NullValueHandling.Include,
                .ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
                .ContractResolver = New Newtonsoft.Json.Serialization.CamelCasePropertyNamesContractResolver()
            }
        })
      
    End Sub

NotasApiController.vb

 <HttpPost()>
    Public Function WebHook(pix As JObject) As HttpStatusCode     
        Dim txId As String = "txidEmpty"
        Dim eid As String = "EidEmpty"    
        Dim jsonResulttodict = JsonConvert.DeserializeObject(Of Dictionary(Of String, Object))(Convert.ToString(pix))
      Dim errText as String =""
        Try
            'Dim obj As JObject = JObject.Parse(pix)
            Dim children As JArray = jsonResulttodict("pix")
            For Each child As JObject In children
                txId = child("txid")
                eid = child("endToEndId")
            Next         
 WriteLog(txId, eid, errText) 'escreva no log e aqui tbm pode incluir o código para atualizar o seu banco de dados
            Return HttpStatusCode.OK
        Catch ex As Exception
            txId = "err"
            eid = "erro"
          errText = ex.Message
  WriteLog(txId, eid, errText)           
            Return HttpStatusCode.BadRequest
        End Try
        'Redirect("https://xxx.xxx.com")
    End Function

Private Sub WriteLog(txId As String, eid As String, err As String)
        Dim FILENAME As String = System.Web.HttpContext.Current.Server.MapPath("~/Webhook.txt")
        Dim Fs As FileStream = New FileStream(FILENAME, FileMode.Create)
        Using SwFromFileStream As StreamWriter = New StreamWriter(Fs)
            SwFromFileStream.Write(txId)
            SwFromFileStream.Write(vbCrLf)
            SwFromFileStream.Write(eid)
            SwFromFileStream.Write(vbCrLf)
            SwFromFileStream.Write(err)
            SwFromFileStream.Flush()
            SwFromFileStream.Close()
            Fs.Dispose()
            Fs.Close()
        End Using
    End Sub

TestePix.vb

Imports System
Imports Gerencianet.SDK
Imports System.Dynamic
Imports Newtonsoft.Json
Imports System.Security.Cryptography.X509Certificates
Imports RestSharp
Imports RestSharp.Authenticators
Imports BPL.BOL
Imports ZXing
Imports System.Drawing
Imports System.IO
Imports System.Drawing.Imaging
Imports Newtonsoft.Json.Linq
Imports System.Text.Json
Imports System.Text.Json.Serialization
Imports System.Net

Partial Class TestePix
    Inherits System.Web.UI.Page

  Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
       
    Dim client_id As String = hdnClientID.Value
    Dim client_secret As String = hdnClientSecret.Value
        Dim token As String = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.mi6whJYhRMy1HEzvTP-nKJcWhqimF_tWxijt5kr87VI"
    'depois de conseguir autenticar e obter o token, pode colocar o token aqui, pois fica válido por 1 hora e te permite chamar os
    seguintes métodos sem precisar autenticar de novo:
     'CriarPix(token) 'cria o pix
      'GetQrCode(token) 'cria o QrCode do pix
    ' SetWebHook(token) 'cadastrar webhook
      ' CheckWebHook(token) 'consultar webhook           
    'CheckPayment(token) ' verificação direta se o pix foi pago
    '
    Try
      GerarTokenGN(cid, cs) 'gera o token, depois chama o metodo CriarPix que, depois de criar o pix, chama o Metodo GetQRCode
      'CriarPix(token) 'cria o pix
      'GetQrCode(token) 'cria o QrCode do pix
      ' SetWebHook(token) 'cadastrar webhook
      ' CheckWebHook(token) 'consultar webhook           
      'CheckPayment(token) ' verificação direta se o pix foi pago
        Catch ex As Exception
            ShowMessage(ex.Message)
        End Try
    End Sub
  
    'acrescentei X509KeyStorageFlags.MachineKeySet na inicilaização do certificado, senão dá erro no servido remoto.
    'Também é preciso acrescentar System.Net.Http.dll no bin para funcionar no remoto.
    
    Public Async Sub GerarTokenGN(ByVal client_id As String, ByVal client_secret As String)
        Dim certPath As String = Server.MapPath("~/BolsasPixCert.p12")
        Dim uidCert As X509Certificate2 = New X509Certificate2(certPath, "",X509KeyStorageFlags.MachineKeySet)
        Dim options = New RestClientOptions("https://pix.api.efipay.com.br") With {
                .ClientCertificates = New X509CertificateCollection() From {
            uidCert
        }
            }

        Dim client = New RestClient(options)
        Dim request = New RestRequest("/oauth/token", Method.Post)
        request.AddHeader("Authorization", "Basic " & System.Convert.ToBase64String(Encoding.ASCII.GetBytes(String.Format("{0}:{1}", client_id, client_secret))))
        request.AddHeader("Content-Type", "application/json")
        request.AddParameter("application/json", "{""grant_type"":""client_credentials"",""client_id"":""" & client_id & """,""client_secret"":""" & client_secret & """}", ParameterType.RequestBody)
        Dim restResponse As RestResponse = Await client.ExecuteAsync(request)
        Dim statusCode As HttpStatusCode = restResponse.StatusCode
        Dim statusCodeNumber As Integer = CInt(statusCode)
        Dim response As String = restResponse.Content
        Label1.Text = response
        If statusCodeNumber = 200 Then
            Dim jsonResulttodict = JsonConvert.DeserializeObject(Of Dictionary(Of String, Object))(Convert.ToString(response))         
            Dim token As String = jsonResulttodict.Item("access_token") 'jsonData.access_token           
            CriarPix(token)         
        Else
            ShowMessage("Erro credenciais:" & statusCodeNumber)
        End If
    End Sub
   
    Private Async Sub CriarPix(token As String)
       Dim client_id As String = hdnClientID.Value
    Dim client_secret As String = hdnClientSecret.Value
        Dim certPath As String = Server.MapPath("~/BolsasPixCert.p12")
        Dim uidCert As X509Certificate2 = New X509Certificate2(certPath, "")
        Dim options = New RestClientOptions("https://pix.api.efipay.com.br") With {
                .MaxTimeout = -1,
                 .ClientCertificates = New X509CertificateCollection() From {
            uidCert
        }
            }
        Dim client = New RestClient(options)
        Dim request = New RestRequest("/v2/cob", Method.Post)
        request.AddHeader("Authorization", "Bearer " + token)
        request.AddHeader("Content-Type", "application/json")
        Dim body = New With {
            .calendario = New With {
                .expiracao = 3600
            },
            .devedor = New With {
                .cpf = "52537188266",
                .nome = "Jake Harper"
            },
            .valor = New With {
                .original = "0.01"
            },
            .chave = "63b4dcb1-1afb-455a-acd3-edff14a0bxxx",
            .solicitacaoPagador = "Taxa Inscrição Processo Seletivo"
        }
        request.AddParameter("application/json", body, ParameterType.RequestBody)
        Dim restResponse As RestResponse = Await client.ExecuteAsync(request)
        Dim statusCode As HttpStatusCode = restResponse.StatusCode
        Dim statusCodeNumber As Integer = CInt(statusCode)
        If statusCodeNumber = 201 Then
            Dim response As String = restResponse.Content
            Dim jsonResulttodict = JsonConvert.DeserializeObject(Of Dictionary(Of String, Object))(Convert.ToString(response))
            Dim locID As String = jsonResulttodict.Item("loc")("id")
            Dim txID As String = jsonResulttodict.Item("txid")
                  If SaveTxID(txID) Then 'salvar txid no banco de dados
                  Label1.Text = response
                    GetQrCode(token, locID) 'gerar o qr code
                  End If
        Else
            ShowMessage("Erro Gerar Pix:" & statusCodeNumber)
        End If
    End Sub

    Private Async Sub GetQrCode(token As String, locID As String)
    Dim client_id As String = hdnClientID.Value
    Dim client_secret As String = hdnClientSecret.Value
        Dim certPath As String = Server.MapPath("~/BolsasPixCert.p12")
        Dim uidCert As X509Certificate2 = New X509Certificate2(certPath, "")

        Dim options = New RestClientOptions("https://pix.api.efipay.com.br") With {
                .MaxTimeout = -1,
                 .ClientCertificates = New X509CertificateCollection() From {
            uidCert
        }
            }
        Dim client = New RestClient(options)
        Dim request = New RestRequest("/v2/loc/" & locID & "/qrcode", Method.Get)
        request.AddHeader("Authorization", "Bearer " + token)
       
        Dim restResponse As RestResponse = Await client.ExecuteAsync(request)
        Dim statusCode As HttpStatusCode = restResponse.StatusCode
        Dim statusCodeNumber As Integer = CInt(statusCode)
        If statusCodeNumber = 200 Then
            Dim response As String = restResponse.Content
            Dim jsonResulttodict = JsonConvert.DeserializeObject(Of Dictionary(Of String, Object))(Convert.ToString(response))

                      Image1.ImageUrl = jsonResulttodict.Item("imagemQrcode") 'mostrar qr code na tela
            txtQrCode.Text = jsonResulttodict.Item("qrcode")
        Else
            ShowMessage("Erro QrCode:" & statusCodeNumber)
        End If
    End Sub
                  
                  Private Function SaveTxID(txID As String) As Boolean 'salvando o txId no banco de dados
        Dim pid As Integer = 3
        Dim objPremat As New Premat
        objPremat.PrematID = pid
        objPremat.TxID = txID
        Try
            Premat.SetTxID(objPremat)
            Return True
        Catch ex As Exception
            ShowMessage("Erro ao atualizar Código transação: " & ex.Message)
            Return False
        End Try
    End Function

    Private Async Sub SetWebHook(token As String) 'cadastrar o webhook
       Dim client_id As String = hdnClientID.Value
       Dim client_secret As String = hdnClientSecret.Value
        Dim certPath As String = Server.MapPath("~/BolsasPixCert.p12")
        Dim uidCert As X509Certificate2 = New X509Certificate2(certPath, "")
        Dim options = New RestClientOptions("https://pix.api.efipay.com.br") With {
                .MaxTimeout = -1,
                 .ClientCertificates = New X509CertificateCollection() From {
            uidCert
        }
            }
        Dim client = New RestClient(options)
        Dim request = New RestRequest("/v2/webhook/63b4dcb1-1afb-455a-acd3-edff14a0bxxx", Method.Put)
        request.AddHeader("Authorization", "Bearer " + token)       
        request.AddHeader("x-skip-mtls-checking", "true") 'host compartilhado
        Dim body = New With {
                          .webhookUrl = "https://meusite.com.br/api/NotasApi/WebHook"
        }
        request.AddParameter("application/json", body, ParameterType.RequestBody)
        Dim restResponse As RestResponse = Await client.ExecuteAsync(request)
        Dim statusCode As HttpStatusCode = restResponse.StatusCode
        Dim statusCodeNumber As Integer = CInt(statusCode)
        Dim response As String = restResponse.Content
        Label1.Text = response
        If statusCodeNumber = 201 Then
            Label1.Text = "tudo ok"
        Else
            ShowMessage("Erro Cadastrar WebHook:" & statusCodeNumber)
        End If
    End Sub
                      
    Private Async Sub CheckWebHook(token As String)
       Dim client_id As String = hdnClientID.Value
        Dim client_secret As String = hdnClientSecret.Value
        Dim certPath As String = Server.MapPath("~/BolsasPixCert.p12")
        Dim uidCert As X509Certificate2 = New X509Certificate2(certPath, "")
        Dim options = New RestClientOptions("https://pix.api.efipay.com.br") With {
                .MaxTimeout = -1,
                 .ClientCertificates = New X509CertificateCollection() From {
            uidCert
        }
            }
        Dim client = New RestClient(options)
        Dim request = New RestRequest("/v2/webhook/63b4dcb1-1afb-455a-acd3-edff14a0bxxx", Method.Get)
        request.AddHeader("Authorization", "Bearer " + token)
        Dim restResponse As RestResponse = Await client.ExecuteAsync(request)
        Dim statusCode As HttpStatusCode = restResponse.StatusCode
        Dim statusCodeNumber As Integer = CInt(statusCode)
        Dim response As String = restResponse.Content
        Label1.Text = response
        If statusCodeNumber = 201 Then
        Else
            ShowMessage("Erro Cadastrar WebHook:" & statusCodeNumber)
        End If
    End Sub

       Private Async Sub CheckPayment(token As String) 'verficar pagto direto através do txid
       Dim client_id As String = hdnClientID.Value
        Dim client_secret As String = hdnClientSecret.Value
        Dim certPath As String = Server.MapPath("~/BolsasPixCert.p12")
        Dim uidCert As X509Certificate2 = New X509Certificate2(certPath, "")
        Dim options = New RestClientOptions("https://pix.api.efipay.com.br") With {
                .MaxTimeout = -1,
                 .ClientCertificates = New X509CertificateCollection() From {
            uidCert
        }
            }
        Dim client = New RestClient(options)
                              Dim request = New RestRequest("/v2/cob/0fa59ef355a94b809cdae74df1fb2030", Method.Get) 'txid
        request.AddHeader("Authorization", "Bearer " + token)      
        Dim restResponse As RestResponse = Await client.ExecuteAsync(request)
        Dim statusCode As HttpStatusCode = restResponse.StatusCode
        Dim statusCodeNumber As Integer = CInt(statusCode)
        Dim response As String = restResponse.Content
        Label1.Text = response
        If statusCodeNumber = 200 Then
            Dim jsonResulttodict = JsonConvert.DeserializeObject(Of Dictionary(Of String, Object))(Convert.ToString(response))
            Label1.Text = jsonResulttodict.Item("status")
        Else
            ShowMessage("Erro Consultar Pix:" & statusCodeNumber)
        End If
    End Sub
                                
      Protected Sub ShowMessage(ByVal msg As String)
        If Not String.IsNullOrEmpty(msg) Then
            divMsg.Style("padding") = "20px"
            divMsg.InnerHtml = msg
            ' ClientScript.RegisterStartupScript(Me.GetType(), "hash", "location.hash = '#premat';", True)
        End If
    End Sub                           
End Class

Fiz esses gists, visto que a sdk .NET framework que a Efi disponibiliza no github não tem nada relacionado ao pix. Então tive que ir implementando tudo manualmente: Autenticação, Criar Pix, Criar Qr Qode, Cadastrar WebHook, Consultar WebHook, Configurar o recebimento de Callbacks e Verificação Direta de Status de um pix. E no discord da Efi, tbm não consegui ter ajuda de gente que já fez isto no .NET framework.