UpdateObject

Ex1.cs

// Example 1: Simply updating an entity does not work if not calling UpdateObject

            string tableName = "testupdate";
            string partition = "Customers";
            client.GetTableReference(tableName)
                  .CreateIfNotExists();

            var rowKey = DateTime.Now.ToString("HHmmss");

            // User A creates customer.
            var contextUserA = new TableServiceContext(client);
            contextUserA.AddObject(tableName, new SomeEntity()
            {
                Name = "Jack",
                PartitionKey = partition,
                RowKey = rowKey
            });
            contextUserA.SaveChanges();

            // User B fetches customer Jack.
            var contextUserB = new TableServiceContext(client);
            var entityUserB = contextUserB.CreateQuery<SomeEntity>(tableName)
                                       .Where(o => o.PartitionKey == partition && o.RowKey == rowKey)
                                       .FirstOrDefault();

            // User C fetches customer Jack.
            var contextUserC = new TableServiceContext(client);
            var entityUserC = contextUserC.CreateQuery<SomeEntity>(tableName)
                                       .Where(o => o.PartitionKey == partition && o.RowKey == rowKey)
                                       .FirstOrDefault();

            // Update does not do anything since we didn't call UpdateObject.
            entityUserB.Name = "Rambo";
            contextUserB.SaveChanges(SaveChangesOptions.ReplaceOnUpdate);
            entityUserC.Name = "Jesus";
            contextUserC.SaveChanges(SaveChangesOptions.ReplaceOnUpdate);      

Ex2.cs

// Example 2: Updating the entity works, but causes concurrency exception

            string tableName = "testupdate";
            string partition = "Customers";
            client.GetTableReference(tableName)
                  .CreateIfNotExists();

            var rowKey = DateTime.Now.ToString("HHmmss");

            // User A creates customer.
            var contextUserA = new TableServiceContext(client);
            contextUserA.AddObject(tableName, new SomeEntity()
            {
                Name = "Jack",
                PartitionKey = partition,
                RowKey = rowKey
            });
            contextUserA.SaveChanges();

            // User B fetches customer Jack.
            var contextUserB = new TableServiceContext(client);
            var entityUserB = contextUserB.CreateQuery<SomeEntity>(tableName)
                                       .Where(o => o.PartitionKey == partition && o.RowKey == rowKey)
                                       .FirstOrDefault();

            // User C fetches customer Jack.
            var contextUserC = new TableServiceContext(client);
            var entityUserC = contextUserC.CreateQuery<SomeEntity>(tableName)
                                       .Where(o => o.PartitionKey == partition && o.RowKey == rowKey)
                                       .FirstOrDefault();

            // Update works.
            entityUserB.Name = "Rambo";
            contextUserB.UpdateObject(entityUserB);
            contextUserB.SaveChanges(SaveChangesOptions.ReplaceOnUpdate);
            // This causes an exception, the ETag on the server is different since we updated the entity on the previous line.
            entityUserC.Name = "Jesus";
            contextUserC.UpdateObject(entityUserC);
            contextUserC.SaveChanges(SaveChangesOptions.ReplaceOnUpdate);  

Ex3.cs

// Example 3: Even though the ETag on the server is different, saving works (uncond. update)

            string tableName = "testupdate";
            string partition = "Customers";
            client.GetTableReference(tableName)
                  .CreateIfNotExists();

            var rowKey = DateTime.Now.ToString("HHmmss");

            // User A creates customer.
            var contextUserA = new TableServiceContext(client);
            contextUserA.AddObject(tableName, new SomeEntity()
            {
                Name = "Jack",
                PartitionKey = partition,
                RowKey = rowKey
            });
            contextUserA.SaveChanges();

            // User B fetches customer Jack.
            var contextUserB = new TableServiceContext(client);
            var entityUserB = contextUserB.CreateQuery<SomeEntity>(tableName)
                                       .Where(o => o.PartitionKey == partition && o.RowKey == rowKey)
                                       .FirstOrDefault();

            // User C fetches customer Jack.
            var contextUserC = new TableServiceContext(client);
            var entityUserC = contextUserC.CreateQuery<SomeEntity>(tableName)
                                       .Where(o => o.PartitionKey == partition && o.RowKey == rowKey)
                                       .FirstOrDefault();

            // Update works.
            entityUserB.Name = "Rambo";
            contextUserB.UpdateObject(entityUserB);
            contextUserB.SaveChanges(SaveChangesOptions.ReplaceOnUpdate);
            // No exception.
            entityUserC.Name = "Jesus";
            contextUserC.Detach(entityUserC);
            contextUserC.AttachTo(tableName, entityUserC, "*");
            contextUserC.UpdateObject(entityUserC);
            contextUserC.SaveChanges(SaveChangesOptions.ReplaceOnUpdate);