Difference between save and savechanges in lightswitch

Question

Hi

What is the difference between

this.save() and this.DataWorkspace.ApplicationData.SaveChanges();

Regards

Karan Gupta

Answer 1

The first one, this.Save, is found in screen methods, & causes the changes made during that screen to be saved. Underneath the covers, it's calling this.DataWorkspace.ApplicationData.SaveChanges.

The second one, this.DataWorkspace.ApplicationData.SaveChanges, is working at the Data Source level & causes the changes made during the life of the DataWorkspace to be saved.

In what scenario are you considering using either of them?

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Yann - LightSwitch Central - Click here for FREE Themes, Controls, Types and Commands

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Answer 2

Hi Yann

Sorry for the late reply. Can you please elaborate this with the help of an example.

Answer 3

Not without you giving me a scenario to work with, sorry.

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Yann - LightSwitch Central - Click here for FREE Themes, Controls, Types and Commands

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Answer 4

Hi Yann

Thanks for the reply. I am not looking for the scenario in which I can use both the methods i.e. save() and savechanges(). But I am looking for 2 scenarios where save()  will work fine and other scenario  where savechanges() will work fine.

Answer 5

Hi Karan,  For example, in screen command method,  if you just call SaveChangs method instead of Save method,  you won't get validaton message if there is a validation error, and the screen won't be froze,  if the savechangs takes a lot of time you will see the difference.

Answer 6

Hi ryan lin chinese

I have created a employee table which contains 2 fields

1. EmployeeName (string)

2. Age(integer)

I have put a validation that if the age is lesser than 18 then give a validation error message.

Now when I enter the data and click save button which contains this.save() code I am getting thei error -  "Please correct data entry errors and try to save again."

and when I click the button which contains this.Dataworkspace.ApplicationData.SaveChanges() then I am getting this error - "The operation cannot be performed because one or more objects are invalid.  Please inspect the ValidationException.ValidationResults property for more information."

Have I missed something while trying a POC.

Please advice

Regards

Karan Gupta

Answer 7

Calling the SaveChanges method on a data service (ApplicationData) will throw an exception if the save operation did not complete successfully. Such exceptions can be caused by:

• Validation errors
• Concurrency conflicts
• Connection errors and timeouts

This is not a complete list, but gives you an idea of the types of issues that can occur. The method throws the exceptions to allow you to handle the exceptions in your code and possibly provide an automated way of recovering from the problems.

Calling the Save method on the screen calls the SaveChanges method on the data service at some point (as Yann has mentioned) and handles specific exceptions to provide a decent experience to the end user. It handles, among others, concurrency and validation exceptions. Concurrency exceptions are handled by showing the concurrency resolver dialog to allow the end user to manually determine how to resolve conflicts. Validation exceptions are handled by showing the message that you saw: "Please correct data entry errors and try to save again."

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Justin Anderson, LightSwitch Development Team

Answer 8

Hello, I have a problem regarding "dirty" data in a DataGrid at startup and probably is depended to Save() vs. SaveChanges(), but really I don't have idea what happens

DataGrid cache rows