I have table with this structure ID PK and two columns with FK for example ActivityID and ContactID.
I try programmatically insert some value in this two FK columns.
How can I do this, any help is appriciated.Tnx
If you want to use your structure - you have to get instances of Activity and of Contact and just set corresponding properties on new entity.
var newActivityContact = new ActivityContact();// m_Entities.CreateActivityContact(0);
newActivityContact.Activity = activityRepository.GetById(activityId);
newActivityContact.Contact = contactRepository.GetById(contactId);
m_Entities.AddToActivityContact(newActivityContact);
m_Entities.SaveChanges();
I think the best solution would be to get rid of primary key, set up combination of ActivityID and ContactID as PK and then recreate whole model in visual designer. Every Activity object will have Contacts navigation property and every Contact will have Activities. You will be able to add contacts to activity by calling:
activity.Contacts.Add(contact);
If you really need additional ID, it will be more complicated.
Related
I have a Customer table and another Orders table. Each Customer can have many orders (One to many relationship).
I want to get a Customer object and from it get how many orders he has (the actual order data is not relevant at this point). So as I see it I have 2 options:
create a view with another OrdersCount field - and that will be another object in my system.
in my app, when I need the count get the Customer.Orders.Count - but for my understanding that will cause an extra query to run and pull all the orders from the database to that collection.
Is there a correct way to do such thing?
Thanks
You do need a new type, but you don't need to recreate all relevant properties.
from c in context.Customers
// where ...
select new {
Customer = c,
OrderCount = c.Orders.Count()
}
Update code that looks for e.g. the Name property of an item in the result, to look for Customer.Name.
I am using Breeze (http://www.breezejs.com/) and to use the functionality I want it requires mapping to a complete entity and all of its fields. I have a "Person" entity, but it includes a Social Security Number field. I want to keep this SSN# field private so I would like to create an entity named SubSetPerson that is updateable, has navigation properties and only contains the columns I want (e.g. ID, FirstName, LastName, myNavigationProperty) and does not contain the SSN#. I am using database/model first. Is this possible?
If you are using database first, then you could create a view for that table which only selects the columns you want. Then update the EF model browser to include that view.
Try using a Master-Detail type structure for your person. The master table would contain the person's public information; ie name, birthdate, etc... The detail table would contain only the more sensitive information (SSN, etc...). Then depending on your needs you can load the detail or not.
Let's say I have two tables: table Category and table Book
I would like to add a Category, then use its ID for inserting a book (which has a CategoryId field pointing to the table Category).
To get this info, I now commit my changes after inserting the category as it is not provided otherwise.
Is there a way to point to this category when inserting my book without commiting after inserting the category?
Thanks in advance
If the ID is generated by the database, then no, you can't get it until it is committed
It sounds like you have a FK relationship setup. If that's the case, if you associate the Category and Book entities together - EF should be create the necessary FK's.
For example:
var Category = new Category();
Book.Category = Category;
context.Books.Add(Book);
context.SaveChanges();
Would create a book, and a category and depending on how your mapping is setup the proper fields should be set. Can you post your model if this is not the case?
I have 3 normalised tables consisting of Employees, Departments and EmployeesToDepartments. I wish to be able to assign an Employee to one or more Department, hence the link table (EmployeesToDepartments). I can successfully query the database and extract the full hierarchy of entities via the Navigation properties using
this.ObjectContext.Employees.Include("EmployeesToDepartments").Include("EmployeesToDepartments.Department")
plus the [Include] attribute in the metadata, thus allowing me to access the Departments for a given Employee. Upon trying to remove a link between an [Employee] and [Department] in the [EmployeesToDepartments] table I was given a Foreign Key Constrain error.
I have simplified my model to include just one navigation property between [Employees] and [EmployeesToDepartments]. A Foreign Key constraint between[Employees].[ID] and [EmployeesToDepartments].[IDEmployee] was preventing me from updating the EmployeesToDepartments table. With this removed via a Relationship setting I can now update the table. I can now execute the following code
foreach (var rel in _employee.EmployeesToDepartments)
{
_employee.EmployeesToDepartments.Remove(rel);
}
_domainContext.SubmitChanges();
without error.
I was expecting to see the entries in the RelEmployeesToDepartments with the IDEmployee to have been deleted. What I see in the table are the value 0 where the IDEmployee previously was.
Is it possible to force a DELETE statement to be issued? Am I misunderstanding the basic concepts here?
Any help would be much appreciated.
Removing entities in navigation property only breaks the link between entities. You have to delete from the EntitySet to achive what you want.
ex)
myDomainContext.EmployeeDepartments.Remove(employeeDepartmentToRemove);
myDomainContext.SubmitChanges();
OK, I have 3 tables, call them:
Person
PersonID
Name
Store
StoreID
Name
PersonStore
PersonID
StoreID
Now, I have a form which allows you to add stores to a person. However, I am getting the store ID back from the form. I don't really want to do a query to get the store object from Entity Framework. I just want to add to the table using the StoreID and the Person object which I have.
By default in EF this join table won't appear as an entity instead you'll get a many to many relationship which will show up as two navigation properties
i.e.
Person.Stores
Store.People
If you want to build a many to many relationship without retrieving the entities then attaching stub entities is the best way.
var person = // you already have the person
var store = new Store{StoreID = 5} // you know the storeID
ctx.AttachTo("Stores", store);
ctx.AttachTo("People", person); // assuming the person isn't already attached
person.Stores.Add(store);
ctx.SaveChanges();
The only problem with this code is it will fail if the relationship already exists, so you need to be sure you are creating a new relationship
For more on using Stub entities like this check out my post.
Hope this helps.
Alex
Edit from OP:
Since I am using EF4, I used the following code to remove the string from the attach (thanks to tip 13 from the link).
var person = // you already have the person
var store = new Store{StoreID = 5} // you know the storeID
ctx.Stores.Attach(store);
person.Stores.Add(store);
ctx.SaveChanges();