Updating records using linq
The following method marks a single product as discontinued, based on the product ID: As you can see, I’m using a simple LINQ query to get a single product with a Product ID matching the product ID parameter of the method, setting the Discontinued flag, and saving the changes. Let’s say I wanted to discontinue all products which are out of stock and have no units on order, instead of just one.The overhead of this is a little bit more than if I were using ADO. In this case I have to execute one database call to retrieve the product, and one database call to update the data. Using only the built-in Entity Framework functionality, I would have to do something like this: This LOOKS pretty simple – I’m iterating through the context. Behind the scenes, Entity Framework is executing one SQL ‘select’ call to retrieve all the products, but when you call Save Changes, it is executing one SQL ‘update’ call . Product_Id = id, but how do I pass the update statement.If the same window will be used for the form to update a record and add a record, then the Accept button will be the single button to start the task. = null) //here logic of what should happend if there is something in db else Here if I make similar checks for updating records ? In a previous article I discussed performing bulk updates with Entity Framework.
As the number of out of stock products in the Products table grows, the number of SQL statements executed grows.Finally, six months later, I found someone who agreed that this was a problem and created his own solution.Paul Welter of Lore created a library called Entity Framework.Previous to Entity Framework, you would have used ADO. Entity Framework 6.1, in particular, introduced a Mapping API which exposes the internal object-to-entity mapping schema.Net to open a database connection, create a command object, execute a SQL statement, iterate through the results and create your C# class instances (objects) manually. Updating individual records in Entity Framework is straightforward and relatively simple: create a context, load the record to be updated, update the properties, and save the changes.
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Extended which allows you to (among other features not covered by this article) perform batch Update and Delete statements using a single SQL call. Extended library used reflection to access internal (private and protected) properties and methods of the various Entity Framework classes.