Could not load file or assembly 'System.Transactions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. Either a required impersonation level was not provided, or the provided impersonation level is invalid. (Exception from HRESULT: 0x80070542)

IPrincipal threadPrincipal = System.Threading.Thread.CurrentPrincipal;

            if (!string.IsNullOrEmpty(threadPrincipal.Identity.Name))
            {
                mainLogger.MainLogger.InfoFormat("Name: {0}\nIsAuthenticated: {1}" + "\nAuthenticationType: {2}",
                    threadPrincipal.Identity.Name,threadPrincipal.Identity.IsAuthenticated,threadPrincipal.Identity.AuthenticationType);
            }

Name: домен\юзер1_1
IsAuthenticated: True
AuthenticationType: NTLM

using(SqlConnection c = new ...)
{

c.Open(); <---------- здесь эксцепция

}

Could not load file or assembly 'System.Transactions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. Either a required impersonation level was not provided, or the provided impersonation level is invalid. (Exception from HRESULT: 0x80070542)

[OperationBehavior( Impersonation = ImpersonationOption.Allowed)] // Required )] <--- в статье так, но не думаю, что это важно
public bool Test()
{
  using ( ServiceSecurityContext.Current.WindowsIdentity.Impersonate( ) )
  {
   // здесь уже нужный юзер, контекст сменён(!)

     con.Open();// <-- exception, incorrect sql server instance name и т.д.