System.Xml.XmlException DTD is prohibited in this XML document Exception

I am trying to do SSO through ADFS while passing the URL through IDpSsoDescriptor. Issue I am facing:

System.Xml.XmlException HResult=0x80131940 Message=For security reasons DTD is prohibited in this XML document. To enable DTD processing set the DtdProcessing property on XmlReaderSettings to Parse and pass the settings into XmlReader.Create method. Source=ITfoxtec.Identity.Saml2 StackTrace:

I have tried:

XmlReaderSettings settings = new XmlReaderSettings();
settings.DtdProcessing = DtdProcessing.Parse;

But not possible to edit methods in dll.