private void CreateSendDef()
        {
            SoapClient framework2 = new SoapClient();
            framework2.ClientCredentials.UserName.UserName = "XXX";
            framework2.ClientCredentials.UserName.Password = "XXX";
            String requestID;
            String status;

            EmailSendDefinition sd = new EmailSendDefinition();
            sd.CustomerKey = "API Send Definition to DE";
            sd.Name = "API Send Definition to DE";
            SendClassification sc = new SendClassification();
            sc.Name = "Default Commercial";
            sc.CustomerKey = "2239";
            sd.SendClassification = sc;
            SendDefinitionList sdl = new SendDefinitionList();
            sdl.CustomObjectID = "8699590d-8962-de11-8767-001e0bcf2c98"; //This is the ObjectID of the Data Extension, you will need to do a retrieve to find this
            sdl.DataSourceTypeID = DataSourceTypeEnum.CustomObject;
            sdl.DataSourceTypeIDSpecified = true;
            sdl.SendDefinitionListType = SendDefinitionListTypeEnum.SourceList;
            sdl.SendDefinitionListTypeSpecified = true;
            sd.SendDefinitionList = new SendDefinitionList[] { sdl };

            Email em = new Email();
            em.ID = 3096380;
            em.IDSpecified = true;
            sd.Email = em;

            CreateResult[] cresults = framework2.Create(new CreateOptions(), new APIObject[] { sd }, out requestID, out status);

            foreach (CreateResult result in cresults)
            {
                MessageBox.Show(result.StatusMessage);
            }

            MessageBox.Show(requestID + ": " + status);
        }