Solved

LINQ ReQuery

Posted on 2010-08-13
6
887 Views
Last Modified: 2013-11-11
LINQ queries seem to run once and reuse the selected data if the parameters don't change. - even it the data underneath has changed. In this code the query data is not refreshed eventhough I have changed the data in the database and I want to get the refreshed data.

    '** Load Default MWH Data
    Private Sub LoadDefaultMWH()
        '* DataContext is dc_MD
        '* Table is MD_MeterPoints
        Dim wrkMWH As Double
        '** Load Selected Date data
        Dim qDM = From DM In dc_MD.MD_MeterPoints _
          Select DM Where DM.P_ID = 210

        For Each recDM In qDM                                      '* there is only 1 record
            wrkMWH = recDM.P_DefaultAvailibility
        Next

How can I get LINQ to go back to the database when it thinks it already has what I want?

Thanks!

0
Comment
Question by:BEDMDunphy
  • 2
  • 2
  • 2
6 Comments
 
LVL 18

Expert Comment

by:Anil Golamari
ID: 33431849
Dim qDM = From DM In dc_MD.MD_MeterPoints
                  Where DM.P_ID == 210
                  Select DM

Try this code.
0
 
LVL 18

Expert Comment

by:Anil Golamari
ID: 33431926
I miss typed = twice.
0
 

Author Comment

by:BEDMDunphy
ID: 33432402
I see that you reversed the order of the WHERE and Select... I tried it but I get the same results. As an additional clue, I only get the refreshed data in this query if I actually close the application. I can see the updated data in another application function without closint the application.
0
The New “Normal” in Modern Enterprise Operations

DevOps for the modern enterprise offers many benefits — increased agility, productivity, and more, but digital transformation isn’t easy, especially if you’re not addressing the right issues. Register for the webinar to dive into the “new normal” for enterprise modern ops.

 
LVL 63

Accepted Solution

by:
Fernando Soto earned 500 total points
ID: 33433225
Hi BEDMDunphy;

When you query the database and it returns records those records are saved in the DataContext. If your data in the database for those same records has changed by another process and you re-query the DB with the same DataContect as the original query the data for those records already in the DataContext will NOT be updated. If you change data in the records that are in the DataContext but have not executed a SubmitChanges the database will not be updated.

To get new changes that are in the database for records that are already in the DataContext execute a Refresh, something like the following :

DataContext.Refresh(RefreshMode.OverwriteCurrentValues, TheEntityTable)

For example

dc_MD.Refresh(RefreshMode.OverwriteCurrentValues, MD_MeterPoints)

Then the DataContext will have all the new values for the table MD_MeterPoints.

If you make changes to the DataContext you must do the following for the database to see them :

dc_MD.SubmitChanges()

Fernando
0
 

Author Comment

by:BEDMDunphy
ID: 33453338
Hi FernandoSOTO,

THANKS! For general information for other researchers on this issue - I did have to change the syntax slightly...

dc_MD.Refresh(RefreshMode.OverwriteCurrentValues, dc_MD.MD_MeterPoints)
 
0
 
LVL 63

Expert Comment

by:Fernando Soto
ID: 33453862
Not a problem, glad to help.  ;=)
0

Featured Post

Active Directory Webinar

We all know we need to protect and secure our privileges, but where to start? Join Experts Exchange and ManageEngine on Tuesday, April 11, 2017 10:00 AM PDT to learn how to track and secure privileged users in Active Directory.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Sending an input value from a view to a controller in MVC 3 23
SSRS 2016 Rendering HTML tables 3 31
VB.net Open video relating to control 2 20
Groupbox Control ? 2 19
Creating an analog clock UserControl seems fairly straight forward.  It is, after all, essentially just a circle with several lines in it!  Two common approaches for rendering an analog clock typically involve either manually calculating points with…
Parsing a CSV file is a task that we are confronted with regularly, and although there are a vast number of means to do this, as a newbie, the field can be confusing and the tools can seem complex. A simple solution to parsing a customized CSV fi…
The Email Laundry PDF encryption service allows companies to send confidential encrypted  emails to anybody. The PDF document can also contain attachments that are embedded in the encrypted PDF. The password is randomly generated by The Email Laundr…

830 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question