Concurrency erro when deleteing or updating multiple primary key fields
In that case the code uses the posted form values to create a department entity so that the Edit page can be redisplayed with an error message. code-html Main] Run the app and go to the Departments Index page.
As an alternative, you wouldn't have to re-create the department entity if you display only an error message without redisplaying the department fields. You can use that object to get the new values entered by the user and the current database values. code-csharp Main] The code adds a custom error message for each column that has database values different from what the user entered on the Edit page (only one field is shown here for brevity). code-csharp Main] Finally, the code sets the value will be stored in the hidden field when the Edit page is redisplayed, and the next time the user clicks Save, only concurrency errors that happen since the redisplay of the Edit page will be caught. Right-click the Edit hyperlink for the English department and select Open in new tab, then click the Edit hyperlink for the English department.
In that case, the code sends an error message to the view using to give the Http Post method a unique signature.
(The CLR requires overloaded methods to have different method parameters.) Now that the signatures are unique, you can stick with the MVC convention and use the same name for the Http Post and Http Get delete methods.
Entity Framework Core provides no built-in support for it, and this tutorial doesn't show you how to implement it.
The alternative to pessimistic concurrency is optimistic concurrency.
In that case, the code redirects to the Index page.
If this flag is true and the Department does exist, it was changed by another user.
NET Core MVC web applications using Entity Framework Core and Visual Studio.If you don't enable the detection of such conflicts, whoever updates the database last overwrites the other user's changes.In many applications, this risk is acceptable: if there are few users, or few updates, or if isn't really critical if some changes are overwritten, the cost of programming for concurrency might outweigh the benefit.The following illustrations show the Edit and Delete pages, including some messages that are displayed if a concurrency conflict occurs.A concurrency conflict occurs when one user displays an entity's data in order to edit it, and then another user updates the same entity's data before the first user's change is written to the database.