https://learn.microsoft.com/pt-br/dotnet/api/system.servicemodel.messageheader-1.mustunderstand?view=netframework-4.8.1&viewFallbackFrom=net-10.0-pp
MessageHeaderT.MustUnderstand Property (System.ServiceModel) | Microsoft Learn
Gets or sets a value that indicates whether the header must be understood, as stated in the SOAP 1.1/1.2 specification.
property systemmicrosoftlearn