System.Net.WebException: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.

[Web Service in .net , webservice security]
when call webservice with bad certificate (VB.NET)

1.Add imports 
Imports System.Net.Security
Imports System.Security.Cryptography.X509Certificates

2.before calling webservice:
ServicePointManager.ServerCertificateValidationCallback = New RemoteCertificateValidationCallback(AddressOf customXertificateValidation)

3.Custom certificate runner:
Private Shared Function customXertificateValidation(ByVal sender As Object, ByVal cert As X509Certificate, ByVal chain As X509Chain, ByVal Errora As SslPolicyErrors) As Boolean
        Return True
End Function

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