I have an application with user and admin sections. If an admin updates data with the help of sql datasource then it's updated the database. However, when we retrieve data with linq query then it's showing its old value rather than the updated value.
After some time, the linq query automatically shows the correct value.
I think its caching the value, but I find myself helpless. Please help me with this.
When you say
when we retrieve data with linq query
Do you mean you call your select methods again or are you using the current in memory objects?
In either case, you can always refresh an entity with :
Context.Refresh(System.Data.Linq.RefreshMode.OverwriteCurrentValues, entity)
Make sure that you're using your DataContext efficiently (ideally one per unit of work).
After each update, make sure you call DataContext.SubmitChanges(); to commit your changes back to the database.
Also be aware that any context you instanciate between your changes being added to another context and calling SubmitChanges() will not reflect those changes.
Related
I'm trying to make a query against the table HcmWorker and related.
But i want to figure out how to get the result of the display method HcmWorker.primaryDepartmentName() into it's own field in my query.
I also tried creating a view to execute the function via a ViewMethod but that doesn't seem to work as ViewMethods only inject code into the final query against the view.
I'm NOT making a form. The end result has to come through the QueryService.
Sorry, but what you are trying to do is not possible.
You could calculate a non stored field in the postLoad method, but that would impact every access to your table, and it would most likely not work in the context of a query service.
Users modify a DB object in an edit form that I have, pretty straight forward.
I need to implement a 'change log' on this object. I need to record which fields where changed and what they were before and after. I'm using Razor MVC.
I've done this by writing triggers for the table on update/delete. On update/delete of a record, the trigger pushes the record to a History table, in a History database. This creates the change log. Then you would just need to display it; to identify the change would require evaluating each and every field.
There's nothing already built that wold do this for you that I know of.
I am not sure if it's a bug, but when i add a new view or a new stored procedure to the model it updates all the tables that exist. So my question is should it work like this and if it should how can i add some new procedure without updating the whole model?
Yes, this is the correct functionality when using the "Update Model" function for EntityFramework. It looks at every database object and updates the EF Model to match what it finds in the database. This is, in part, because the designer does not let you specifically choose which tables or view to update, so it verifies any changes in the database. This allows the model to proactively ensure that when it connects to the database there won't be an error based on the database changing.
Hi i have a sql database server runnin on my desktop. I want to create an asp.net application to detect when new data has been inserted into the database. Is there a command in visual studio to detect when theres new data right away?
Use the timestamp datatype on each column. This will stay identical until a change is made to any column in that row. If you combine this with the rowcount you can be certain if anything has changed in your database. You would need to cache the current timestamps and row count and compare them with the results of a query, you can then find out if there is a change.
So in your answer to:
Is there a command in visual studio to
detect when theres new data right
away?
Yes there is, although its not a command is the timestamp function (not to be confused with anything to do with the time)
Perhaps you need to provide more details to your scenario since constant querying of the database might not be the best way forward.
You can get a row count of your dataset and create a application
IN VB
Dim i as Integer
i=dataset.tables("table").rows.count
in sql backed return a count of a table and create a ASP.Net website to get the count and when count change alerts you
It may be heavier duty than you are looking for, but SQL Notification Services will do what you want. Essentially you execute a query and tell notification services you want to be notified whenever re-running that query would produce different results.
if you are using caching you can make it dependent on sql.
or you can fire email using sql trigger so when ever trigger get fired you will receive an email.
otherwise you will have to check your db again and again for any changes.
if you can provide more details about exact situation , we can provide more specific solution
You can create a webservice and call it using javascript.
here you can find sample how to call webservice using javascript:
function CallWebservice()
{
myWebService.isPrimeNumberWebService.callService(isPrimeNumberResult, "IsPrime",
testValue.value);
setTimeout("CallWebservice()",100);//here set time according to your requirement
}
For timer in javascript:
http://dotnetacademy.blogspot.com/2010/09/timer-in-javascript.html
For webservice in javaScript:
http://www.webreference.com/js/tips/020715.html
How to call webservice in JavaScript for FireFox 3.0
Is it possible to add properties to my model that dont exist in the database?
For example I have a calendar table, I want to retireve this data in my MVC controller then work out time left until each entry starts and return this to the view. So I would like another property in my calendar model to hold time left which is a value that I will generate outside of the database.
I've tried just adding the property but when I do that I get errors because the property is not mapped to anything.
Is this even possible?
Thanks
You should be able to add the property to the Model but you will not be able to query it with LINQ. LINQ will ultimately build and expression which it will want to run against the database using SQL. Its at that point that your LINQ will fail to find a mapping from your property to a field somewhere.
If your query returns an IEnumerable of the actual type on which you have created the property your view may be able to access it. I can't remember if EF insists on mapping in that case, it may do.
You might find that you can create subsequent LINQ query that uses LINQ-to-objects if you want to provide some other composite type to your view.
It's a non-persistent property or transient. I don't know Entity Framwork well but with a quick google search you should find the answer.
BTW you can find a lot of tips here :
http://weblogs.asp.net/zeeshanhirani/archive/2008/12/18/my-christmas-present-to-the-entity-framework-community.aspx
After making a quick search myself and a test in VS2008 I don't see a way to exclude a property from the mapping. Maybe it requires you to edit manually the mapping file ? :(