How to update record by linq

For instructions, see Downloading Sample Databases. On the Project menu, click Add New Item. Name the file northwind. Click Add. Expand the Tables folder. This object contains code that you can use to access the Customers table. It also contains code that defines a local Customer object and a Customers collection for the table. The DataContext object for your project is named based on the name of your. For this project, the DataContext object is named northwindDataContext.

The problem with this approach is we now have no way to tell when a caller adds or removes Author s from our Book. What we need is something akin to the EntityRef delegates for OnAdd and OnRemove so that we can perform our synchronization whenever a caller adds or removes an author. Since our data is not in an EntryRef, we need another way to get notifications when an author is added or deleted.

We can do this by making Authors return an ObservableCollection that will notify us when changes are made to it:. The second line authors. This is the delegate method we registered to be notified of all changes made to our Authors collection. Create the method to respond to the Add and Remove events, and use its NotifyCollectionChangedEventArgs to gain access to the items that were added e.

NewItems or removed e. OldItems :. If you've been coding along, then you already did this when you added logic to BookAuthor 's set methods for Book to add the new BookAuthor instance to the Book :. The way this works is that when you attach add the BookAuthor instance to your Book , LINQ to SQL notices the change because it's monitoring Book for changes , and so it will automatically insert this attached BookAuthor record into the database the next time you call SubmitChanges.

Voila, a new BookAuthor relationship. Step 1 calls a RemoveRecord method on the DataContext which we'll add below. The reason it does this is because, unlike any of our other changes made so far, deleting a record always requires direct access to a DataContext. But, we don't want to have to pass the DataContext to our entity classes. We can instead handle this with a static method on the DataContext that:. The method uses Generics so that it can take any record. Warning : If you do choose to create a new DataContext instance for RemoveRecord , you'll have to either:.

Finally, update the code for the other side of your M:M relationship. Here is how that will look for Author :. We're now done updating our classes to handle synchronization. Let's see what it looks like to use those classes to perform M:M updates. Recently, I have discussed about getting started linq to sql in c. That articles also covered for creating select query for retrieving both single and multiple results.

Please use the database structure given below, if you want to try the following examples directly. We just need to create a new object of corresponding database table type, then add it to the DataContext object and then commit the changes. For your information, the above code example is for. NET 3. Just like insert operation, this delete operation example given above will work for. NET framework 3. To edit data, simply first, we will have to retrieve the objects rows and make changes to them wherever needed.

Shaiju T Shaiju T 5, 15 15 gold badges 97 97 silver badges bronze badges. Works like a charm! SaveChanges inside foreach it should be outside foreach loop.

In SQL it is just 1 command that runs on all rows and update the table. The EF code takes all rows first, updates the changed ones on DB, meaning that if you have updated rows, it will execute sql updates — Ashkan Sirous. SaveChanges ; just submits your update. Show 1 more comment. Sign up or log in Sign up using Google.

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