For example, this code, which is the same as before: Will now result in the following database updates when SaveChanges is called: Likewise, if the relationship is severed using either of the examples from above: Then the posts are updated with null foreign key values when SaveChanges is called: See Changing Foreign Keys and Navigations for more information on how EF Core manages foreign keys and navigations as their values are changed. For orphans, the principal/parent entity still exists, but is no longer related to the dependent/child entities. We couldn't quite find a way to update the EF cache after running the stored procedure because that removed both the new AND the old data (I'm assuming EF Core API builds and executes the DELETE statement in the database for the entities whose EntityState is Deleted. The following table shows the result of each OnDelete value on the foreign key constraint created by EF Core migrations or EnsureCreated. Cascade behaviors are configured per relationship using the OnDelete method in OnModelCreating. On a special note, you do not need to have the table having a reference with the On Delete Cascade. If delete rule for Department.employees is also nullify, then when you delete the department, its employees are not let go. Name the project Notes and, to speed things up, check Use Core Dataat the bottom. But if anyone has any alternative suggestion, I'm all ears. If you use entity framework database first, As EF Core always applies configured cascading behaviors to tracked entities. My guess is that this "Delete" Example. DA924x said,  you need to alter your database table with DELETE CASCADE, like this: MSDN Community Support Before proceeding with the demo, here is summary of the effects for update and delete operations: But when management wants to delete the customer records from primary registration table, the records from purchase table should also be deleted. Telerik Data Access helps you to solve this issue while you create the fluent model by allowing you to set the delete rule of the constraints between the tables to CASCADE. Here the parent table is the table specified in the REFERENCING clause of the definition of an enabled foreign key constraint, and the child table is the table on which the enabled foreign key constraint is defined. There may be different rules for each of the update and delete operations on a single FK constraint. Drawing.RecommendationId is still set to the ID of the deleted recommendation and Drawing.Recommendation is set to null. Th… For example: SaveChanges generates the following SQL, using SQL Server as an example: Rather than deleting the blog, we could instead sever the relationship between each post and its blog. Databases can also be configured to cascade nulls like this when a principal/parent in an optional relationship is deleted. On the other hand when I delete the lexikon it will automatically delete the Service which is nice but I also want it to be happen to my Lexikon when I delete my Service. By convention, this relationship is configured as a required, since the Post.BlogId foreign key property is non-nullable. You can handle the cascade only on the Entity DbContext with OnModelCreating. This means that if the application loads all relevant dependent/child entities into the DbContext, as is shown in the examples above, then cascading behaviors will be correctly applied regardless of how the database is configured. Prior to EF Core it didn't have a name and was not possible to change. The configuration options will likely not make sense if the preceding material is not understood. Then the delete successfully removes both the city and the zip code. The Delete value is commonly used when you implement data purging mechanisms, where you need automatic cascade delete between the whole model.. In my previous post oData Service – with INSERT statement, we have already discussed about how to INSERT record into table using GET_ENTITY method. Specify foreign key for the details tables which references to the primary key of master and set Delete rule = Cascade . Add ON DELETE CASCADE To Foreign Key Constraint. Since dependents/children are loaded, they are always deleted by EF Core, and never left for the database to delete. Letting the DB engine do the cascading deletes is 10,000 time more faster than code you have written to do it or letting EF do it. Even though the stored procedure is fast, it's the parsing of the file that takes time (can take on the order of 10 minutes or more), and during that time, If the foreign-key does ADO.NET Entity Framework and LINQ to Entities, If you use entity framework database first, As. That way, it won't touch the database until much later in the process (after which running the stored procedure and saving the new entities will only take Cascading doesn't work because for all the objects I'd like to cascade upon deletion, there will be multiple or cyclical cascade paths which is not allowed (for some bizarre reason) in SQL Server. Well, neither ON DELETE CASCADE nor INSTEAD OF DELETE work. This entity's foreign key value must match the primary key value (or an alternate key value) of the related principal/parent entity. I suppose this is why setting cascade on delete in the data model doesn't work? but attempting to create a SQL Server database with these cascades configured results in the following exception: Microsoft.Data.SqlClient.SqlException (0x80131904): Introducing FOREIGN KEY constraint 'FK_Posts_Person_AuthorId' on table 'Posts' may cause cycles or multiple cascade paths. This can happen because the principal/parent is deleted, or it can happen when the principal/parent still exists but the dependent/child is no longer associated with it. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints. The Entity Framework Core Fluent API OnDelete method is used to specify the action which should take place on a dependent entity in a relationship when the principal is deleted.. The child/dependent can be deleted 2. However, in this case the posts are deleted by the database because it has been configured with ON DELETE CASCADE when it was created. You’ll be auto redirected in 1 second. Optional relationships have nullable foreign key properties mapped to nullable database columns. it hits the database, the database is locked until the transaction is complete. I am running into an issue DELETE CASCADE in Entity Framework Core that I can't seem to find a good solution to. There are two ways to handle this situation: Taking the first approach with our example, we could make the blog-owner relationship optional by giving it a nullable foreign key property: An optional relationship allows the blog to exist without an owner, which means cascade delete will no longer be configured by default. This means there is no longer a cycle in cascading actions, and the database can be created without error on SQL Server. For cascade delete, this severing happens because the principal/parent is itself deleted. For example: Notice that there is no Include for posts, so they are not loaded. 2) Delete stored procedure runs to delete old data. Then I tried allowing EF to automatically cascade deletes: My code shows that the state of the drawing is "modified" after the recommendation is set to deleted. So in that case a single delete query of master table can delete master tables data as well as child tables ... not working in sql 2008. EF will delete a child record(s) (database rows) automatically when its parent is explicitly deleted via the DbContext. Cascade delete and deleting orphans are closely related. If possible, could you please share a simple demo, which could reproduce the issue via OneDrive. Cascading delete refers to the action of removing records associated by a foreign key relationship to a record that is the target of a deletion action. ^ So that's where I'm at now. it just takes a snapshot of the database which, at that point, contains neither the old nor the new entities). Required relationships are configured to use cascade deletes by default. And by a C# transaction, I mean this: ^ This runs on every request/response round from the client to the server (like when the user uploads a files to the point when the data from the file is saved to the database). Why is this not happening? Delete Cascade if foreign keys exists with different delete rule Tom,Q1:----Suppose I have tables t1, t2, t3 and having the relation t1 -> t2 -> t3, where t1 is the root level parent and t3 is the child.Suppose, if there exists a relation between t1 and t2 with delete cascade,t2 and t3 with delete cascade and t1 and t3 with delete restrict.t1 --> Instead you will need to rename the table, create a new table with the foreign key, and then copy the data into the new table. Consider an example of Customer Registration. to be much quicker than doing manual deletions for every single entity (most likely not as fast as the stored procedure but hopefully faster than manual deletions through-and-through). Given all this, there are a number of approaches we tried. We figured if it takes an extra while to delete the entities and then parse the file, that would be fine so long as the final step (saving to The department's employee will be nullified, or in the case of a to-many rule, the department's employees will have an entry removed. Configure the database without one or more of these cascade deletes, then ensure all dependent entities are loaded so that EF Core can perform the cascading behavior. In this article, we explored a few examples on DELETE CASCADE and UPDATE CASCADE rules in SQL Server foreign key. The issue was that this whole procedure is done in a transaction (C#, not SQL), which locks the database. entities manually is exceptionally slow. This can result in circular cascade delete rules, which will cause an exception when you try to add a migration. In the following example, a cascade delete is configured on the relationship between Blog and Post, so the post entity is deleted from the database. However, according to the EFCore docs, a Required relationship will be set to Cascade delete functionality. Change one or more of the relationships to not cascade delete. This article will discuss alternative methods for performing cascading deletes using LINQ to SQL. This means that the foreign key value can be set to null when the current principal/parent is deleted or is severed from the dependent/child. Optional (nullable FK) and required (non-nullable FK) relationships, When dependents/children are loaded and tracked by the DbContext and when they exist only in the database, The default for required relationships like this is. With large files, it will be blocked This one for example: In other words: Do all the parsing of the file first, THEN run the delete stored procedure and save. seconds). The only reason this didn't seem to be an issue before was that between the time when the delete stored procedure was run and the time when it began to parse the file, a new context was injected into the file parsing function. I managed to get cascading to work in EF but I'm still getting an error: "The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. The second option is valid for any kind of relationship and is known as "cascade delete". See Cascade Delete for more details on how cascade delete behaviors work, how they can be configured explicitly and how they are selected by convention. But in any case, I'd like explain our original approach to the problem and why it didn't work. Do not configure cascade delete in the database when soft-deleting entities. Delete Data in Disconnected Scenario in Entity Framework Core. Everyone agreed (and accepted) that this would be somewhat slower than running the stored procedure, but the goal was to minimize the time during which the database is blocked OnDelete accepts a value from the, admittedly confusing, DeleteBehavior enum. Both result in deleting dependent/child entities when the relationship to their required principal/parent is severed. Similarly, we cannot create INSTEAD OF DELETE trigger on the table when a foreign key CASCADE DELETE rule already exists on the table. Many database systems also offer cascading behaviors that are triggered when an entity is deleted in the database. Databases don't typically have any way to automatically delete orphans. 4) Once file parsing is done, new entities are saved to database (with context.SaveChangesAsync()). This is an invalid state, and will cause a referential constraint violation in most databases. Cascade delete allows the deletion of a row to trigger the deletion of related rows automatically. When I was trying to manually delete all drawings, my code looked like this: This worked (no errors) but it's extremely slow. There are three actions EF can take when a principal/parent entity is deleted or the relationship to the child is severed: 1. If you have any compliments or complaints to This can be beneficial to other community members reading this thread. So, you do not save on the amount of query but save on the amount of logic to handle on the C# side because you do not have to care to delete every details. All other values will configure the database to not cascade any changes. :D When deleting a blog, all posts are cascade deleted. This is bad when we have clients trying to view their reports (which is what the API does). it works well. I will see about setting cascade on delete in the database. But I'm not sure if this is the best way. detected (old and new entities conflict). Let's understand it with an easy example. 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