not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.". 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). However, according to the EFCore docs, a Required relationship will be set to Cascade delete functionality. 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 the database is locked, which means no other process can access the database until step 4 above is done. This may cause entities to be accidentally really deleted instead of soft-deleted. If the principal/parent entity is deleted, then the foreign key values of the dependents/children will no longer match the primary or alternate key of any principal/parent. This means that it is usually not possible to sever a relationship without loading both sides into the DbContext. If you have any compliments or complaints to This can be beneficial to other community members reading this thread. :D The child's foreign key values can be set to null 3. Required relationships are configured to use cascade deletes by default. Since dependents/children are loaded, they are always deleted by EF Core, and never left for the database to delete. I'm not too familiar with how As per this guide I modeled it with a PersonAddressjoin-table entity, because this way I can store some extra info. In case you have any questions, please feel free to ask in the comment section below. I figured that if I let EF handle all the work of deleting entities (starting with manual deletions on just a few at the topmost level of the hierarchy), then it's bound For example, if you didn't define the Department.InstructorID property as nullable, EF would configure a cascade delete rule to delete the department when you delete the instructor, which isn't what you want to have happen. 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. When a customer gets registered in a table, some of the records also get stored into the dependent table like their purchasesin purchase table. it just takes a snapshot of the database which, at that point, contains neither the old nor the new entities). IOW, it was trying to save both the new entities AND the old ones. 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 On a special note, you do not need to have the table having a reference with the On Delete Cascade. Add ON DELETE CASCADE To Foreign Key Constraint. Change one or more of the relationships to not cascade delete. The only values that will cause cascading behaviors on the database are Cascade and SetNull. For example, when an author is deleted, it will remove all the related books automatically as … 2) Delete stored procedure runs to delete old data. This means there is no longer a cycle in cascading actions, and the database can be created without error on SQL Server. I'm still not able to get cascading to work in EF and so deleting all the Yes, ON UPDATE CASCADE will update only the columns used in the FK definition. Conclusion. Let's look again at the examples from When cascading behaviors happen, but this time with an optional relationship represented by a nullable Post.BlogId foreign key property: This foreign key property will be set to null for each post when its related blog is deleted. Cascade delete and deleting orphans are closely related. If you use entity framework database first, As The child/dependent can be deleted 2. 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. This is because while EF Core represents relationships using navigations as well of foreign keys, databases have only foreign keys and no navigations. Record of Table SCARR: Step 1: Go to the TCode:… Cascade delete on one-to-one relationships not working #147. Be sure to read sections above before coming here. However, in this case the posts are deleted by the database because it has been configured with ON DELETE CASCADE when it was created. but when I delete my Service the data in table Lexikon will still be in it. We're trying to get cascading to work in EF in the hopes of at least making it a bit faster. The Delete value is commonly used when you implement data purging mechanisms, where you need automatic cascade delete between the whole model.. (and therefore minimize the chances that the client will experience a timeout while trying to view their reports). Please remember to click "Mark as Answer" the responses that resolved your issue, and to click "Unmark as Answer" if not. "Delete" Example. 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.. Do you encounter any exception when update database cascade, please try to delete edmx file, and re-generate again, then check if it works. For example, consider the following model: This model has three relationships, all required and therefore configured to cascade delete by convention: This is all reasonable (if a bit draconian in blog management policies!) I am running into an issue DELETE CASCADE in Entity Framework Core that I can't seem to find a good solution to. DA924x said,  you need to alter your database table with DELETE CASCADE, like this: Our application is database first. For example: Notice that there is no Include for posts, so they are not loaded. Cascade ; SET NULL ; SET Default; It is not necessary that the same rule be applied for both update and delete operations. This table is confusing and we plan to revisit this in a future release. Unable to save changes because a circular dependency was detected in the data to be saved: 'ForeignKey: Profile.InstagramId ... Those tables with a FK should have ON DELETE CASCADE qualifiers. The second option is valid for any kind of relationship and is known as "cascade delete". 1) User uploads file. I've simplified the problem to just two tables: This is a one-to-many relation; every recommendation can have multiple drawings. This is called Cascade deleti… I tell it to delete all records with a foreign key to the record being deleted and then delete the record. 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. Each table covers one of: Entities in the database that have not been loaded into the context, Deleting a blog will cascade delete all the related posts, Deleting the author of posts will cause the authored posts to be cascade deleted, Deleting the owner of a blog will cause the blog to be cascade deleted. 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. EF Core API builds and executes the DELETE statement in the database for the entities whose EntityState is Deleted. Delete Data in Disconnected Scenario in Entity Framework Core. 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. without the old entities after the stored procedure had run). See Relationships for more information on modeling relationships. You’ll be auto redirected in 1 second. 1) Shows how DELETE cascade works -- Parent table CREATE TABLE supplier ( supplier_id numeric(10) not null, supplier_name varchar2(50), contact_name varchar2(50), CONSTRAINT supplier_pk PRIMARY KEY (supplier_id) ); -- children table with foreign key CREATE TABLE products ( product_id … EF Core covers a closely related concept and implements several different delete behaviors and allows for the configuration of the delete behaviors of individual relationships. But in any case, I'd like explain our original approach to the problem and why it didn't work. Here's a super simplified version of my model: User {UserID, Name} Recipe {RecipeID, UserID} Ingredient {IngredientID, UserID} RecipeIngredient {RecipeID, IngredientID} *RecipeIngredient is … 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. 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 But when management wants to delete the customer records from primary registration table, the records from purchase table should also be deleted. Similarly, we cannot create INSTEAD OF DELETE trigger on the table when a foreign key CASCADE DELETE rule already exists on the table. 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. This works great so far... but entity framework doesn't know about Cascading deletes are needed when a dependent/child entity can no longer be associated with its current principal/parent. The original approach was like this: Consider an example of Customer Registration. By convention, this relationship is configured as a required, since the Post.BlogId foreign key property is non-nullable. 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. 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, Do not configure cascade delete in the database when soft-deleting entities. 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. If we know that the database is configured like this, then we can delete a blog without first loading posts and the database will take care of deleting all the posts that were related to that blog. Some databases, most notably SQL Server, have limitations on the cascade behaviors that form cycles. ASP.NET Forums / Data Access / ADO.NET, Entity Framework, LINQ to SQL, NHibernate / Cascade delete entitiyframework core Cascade delete entitiyframework core RSS 1 reply We agreed that we would accept a bit of slowness, but not THIS slow. Since data purging mechanisms are typically handled by an asynchronous process (Timer or BPT), performance is not a concern. I am using Entity Framework Core v1.1.1 and Npgsql v3.2.2. Severing a relationship is not valid here since the dependents/children are not loaded. Optional relationships have nullable foreign key properties mapped to nullable database columns. All other values will configure the database to not cascade any changes. If you use entity framework database first, As This entity's foreign key value must match the primary key value (or an alternate key value) of the related principal/parent entity. We have a web API that sometimes needs to access the database, and while we have a file being uploaded/parsed, it can't. You can not use the ALTER TABLE statement to add a foreign key with cascade delete in SQLite. it. 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. detected (old and new entities conflict). LINQ to SQL does not specifically handle cascading deletes and it is up to the developer to determine whether or not that action is desired. The OnDelete method takes a DeleteBehavior enum as a parameter:. Post.BlogId is a foreign key property, the value of which must match the Post.Id primary key of the post to which the blog belongs. This can be done by setting the reference navigation Post.Blog to null for each post: The relationship can also be severed by removing each post from the Blog.Posts collection navigation: In either case the result is the same: the blog is not deleted, but the posts that are no longer associated with any blog are deleted: Deleting entities that are no longer associated with any principal/dependent is known as "deleting orphans". Instead of delete is a type of trigger I can attach to the delete event on a table. There are two options to avoid this referential constraint violation: The first option in only valid for optional relationships where the foreign key property (and the database column to which it is mapped) must be nullable. If delete rule for Department.employees is also nullify, then when you delete the department, its employees are not let go. Specify foreign key for the details tables which references to the primary key of master and set Delete rule = Cascade . Configuring delete behaviors for related entities when a ... (that is, for tracked dependents). Even though deleting through a stored procedure is by far the fastest way to do it, it might be acceptable if getting cascading to work in EF is at least faster than doing all deletes in EF manually. If the foreign-key does The difference, when there is one, is when the database checks the constraints. This probably stems from past experience of a root delete cascading to an empty database (luckily I … How to Add a Foreign Key with Cascade Delete to an Existing Table. Databases can also be configured to cascade nulls like this when a principal/parent in an optional relationship is deleted. 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. Taking the second approach instead, we can keep the blog-owner relationship required and configured for cascade delete, but make this configuration only apply to tracked entities, not the database: Now what happens if we load both a person and the blog they own, then delete the person? >>Looks like I'm stuck deleting each and every entity manually in code. Using cascading deletes and cascading nulls in the database at the same time will almost always result in relationship cycles when using SQL Server. 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. It is also up to the developer to determine how to go about accomplishing the cascading delete. I use the [CascadeDelete] attribute like follows in an entity, which successfully adds the "Cascade" delete rule to the Parent-Child relation. 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