SQLServer Update Trigger - Reflect changes in LS

Question

Hello,

if I use an update trigger and make some changes in the current row (Data columns = GetDate()...) these changes will not reflect in LS.

will LS not automatically resync the updated row to reflect changes which where made through triggers?

if not how to refresh the current row after update?

robert

Answer 1

I don't think you can refresh the current row but you can refresh the dataset (the table) or the datasource (all tables).

You would probably call the dataset's Refresh method from the screen's Saved event.

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Simon Jones
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Answer 2

I'm wondering that such a fundamental functionality is not supported in LS because many people use triggers and default values in SQLServer.

The only thing i found is to use the Refresh on the object (Table?) in the Saved event but these forces the screen/grid/details whole refresh and the selected row is moved to the first row...

what I need is only a refresh/resync of the rurrent row (in ADO there is a resync method to do this)

robert

Answer 3

LS doesn't support this because it is designed for inexperienced people to make simple systems. It has its own way of setting defaults and of intercepting the "Save Pipeline" to make changes to this and other entities as they are saved.

It may be that this scenario isn't supported by Entity Framework, on which LS is built.

You could remember the key of the current SelectedItem and reposition the SelectedItem after refreshing the collection.

 

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Simon Jones
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Answer 4

I disagree in this point because LS primary Database is SQLServer and it should give us a possibility to use standard SQLServer functions.

Refreshing the current row or select the row after DB Update is a "standard" since ADO Classic...

are you sure that there is no possiblilty to do this?

robert

Answer 5

I do not want to auto refresh another users data - the only thing I want is to have a possibilty to refresh the current row and not the whole set of data...

Answer 6

Hello Simon,

I'm able to save the Key for the selecteditem but how to do the "reposition" because there is no find or a similar method

to go to the right row?

robert

Answer 7

You set the SelectedItem to be the item it was before. How you do this depends on your exact circumstances.

I've done it before in a kind of brute force method (because I needed a generic routine) but it works.

colItems.SelectedItem = GetItemByKey(colItems, strKeyName, objKeyValue)

Friend Function GetItemByKey(ByVal colItems As IVisualCollection, ByVal strKeyName As String, ByVal objKey As Object) As IEntityObject
 
    For Each objItem As IEntityObject In colItems
 
        If objItem.Details.Properties(strKeyName).Value = objKey Then
            Return objItem
        End If
 
    Next
 
    Return Nothing
End Function

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Simon Jones
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Answer 8

I disagree in this point because LS primary Database is SQLServer and it should give us a possibility to use standard SQLServer functions.

Refreshing the current row or select the row after DB Update is a "standard" since ADO Classic...

are you sure that there is no possiblilty to do this?

robert

Currenlty the Default Database is SQL Server Based, but the Lightswitch system is designed to use any Entity Framework Provider supported database, for example you can have a provider for Oracle and it could connect to that... I do not know why but someone could write a provider for Access and it would support that. The system can also have Sharepoint as a datasource, so with that in mind the system would need to use the base functions that are availible in all of the different formats, just designing it for sql server would be limiting.

Answer 9

so with that in mind the system would need to use the base functions that are available in all of the different formats, just designing it for sql server would be limiting.

I believe that this is the reason LightSwitch does not support triggers, meaning they could if they wanted to :)

I would also suggest that triggers are really not a good idea because you are splitting up business logic among multiple layers and triggers can affect sql server performance.

I go way back to SQL Server 97 so I have been using triggers for years, but we used triggers back when we were coding cold fusion and asp+ pages (later they became asp pages then classic asp pages). At that time triggers were the best thing with the best performance.

... that was long time ago :)

Just set the date for a field in the _Created event for an entity.

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Answer 10

LS doesn't support this because it is designed for inexperienced people to make simple systems. 

That may be what some marketing people have said in the past, but that is not something I can agree with :)

I have nearly 60 projects with source code showing professional applications built with LightSwitch like:

Help Desk: An Advanced Visual Studio LightSwitch Application

Using the ComponentOne Excel for Silverlight Control with LightSwitch

A Full CRUD LightSwitch JQuery Mobile Application

A Full CRUD DataJs and KnockoutJs LightSwitch Example Using Only An .Html Page

Shape Your LightSwitch OData Using WCF RIA Services

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http://LightSwitchHelpWebsite.com