Validate method 
    
    
  
Validate request.
    
  Implementation
  @override
void Validate() {
  super.Validate();
  if (this.Attachments.length > 0) {
    EwsUtilities.ValidateParamCollection(this.Attachments, "Attachments");
  }
  if (this.AttachmentIds.length > 0) {
    EwsUtilities.ValidateParamCollection(this.AttachmentIds, "AttachmentIds");
  }
  if (this.AttachmentIds.length == 0 && this.Attachments.length == 0) {
    throw new ArgumentException(
        "CollectionIsEmpty, Attachments/AttachmentIds");
  }
  for (int i = 0; i < this.AdditionalProperties.length; i++) {
    EwsUtilities.ValidateParam(
        this.AdditionalProperties[i], "AdditionalProperties[$i]");
  }
}