ADO.NET :: Cascade Delete - Same Table - Entity Framework 4 Code First
Feb 8, 2011
I been looking but I cant find any info on this topic Anyway I got a model that looks like this.
[Code]....
I want to cascade delete a category with all its sub categories but I cant make that reference in the database, not with the option to cascade update or delete. It work fine with pagecontents and all the other I got its just this same table reference. In NHibernate I do the cascade setting hbm or with a better way using the fluent option. How do I go about this task now?
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Jan 4, 2011
I have two entities (Customer and CustomerRole) and would like to declare many-to-many relationship between them. I can do using the following code:
modelBuilder.Entity<CustomerRole>()
.HasMany(cr => cr.Customers)
.WithMany(c => c.CustomerRoles)
.Map(m => m.ToTable("Customer_CustomerRole_Mapping"));
But it creates the relationship (and the third mapping table) with cascade delete switched off by default. How can I tell EF to create the relationship with cascade delete switched on when using many-to-many?
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Jan 5, 2011
I have an Events table and an InstallmentPlans table. The relationship is 0..1 : an Event can have 0 or 1 Installment plans. If I want to remove the existing InstallmentPlan for an event, how do I do this? Setting it to null doesn't seem to work:
_event.InstallmentPlan = null;
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Feb 9, 2011
I get an cast exception when i am trying to insert an entity in Entity Framework (using code-first). From this code :
public virtual T Insert(T entity)
{
return Context.Set<T>().Add(entity);
}
The cast exception is like "impossible to cast ...Collection'1(Entity) to type (Entity)" I can't figure out why. I am pretty sure ive done everything right. Post entity
public class Post
{
public long PostId { get; private set; }
public DateTime date { get; set; }
[Required]
public string Subject { get; set; }
public User User { get; set; }
public Category Category { get; set; }
[Required]
public string Body { get; set; }
public virtual ICollection<Tag> Tags { get; private set; }
public Post()
{
Category = new Category();
if (Tags == null)
Tags = new Collection<Tag>();
}................................
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Mar 10, 2010
i have 2 tables without any cascade deletind. i wont to delete parent object with all child objects. i do like this
//get parent object
return _dataContext.Menu.Include("ChildMenu").Include("ParentMenu").Include("Pictures").FirstOrDefault(m => m.MenuId == id);
//then i loop all child objects
var picList = (List<Picture>)menu.Pictures.ToList();
//foreach (var item in menu.Pictures)
for (int i = 0; i < picList.Count; i++)
{
if (File.Exists(HttpContext.Current.Server.MapPath(picList[i].ImgPath)))
{
File.Delete(HttpContext.Current.Server.MapPath(picList[i].ImgPath));
}
if (File.Exists(HttpContext.Current.Server.MapPath(picList[i].ThumbPath)))
{
File.Delete(HttpContext.Current.Server.MapPath(picList[i].ThumbPath));
}
//**what must i do here?**
//menu.Pictures.Remove(picList[i]);
// DataManager dm = new DataManager();
// dm.Picture.Delete(picList[i].Id);
//menu.Pictures.de
//_dataContext.SaveChanges();
//picList[i] = null;
}
//delete parent object
_dataContext.DeleteObject(_dataContext.Menu.Include("ChildMenu").Include("ParentMenu").Include("Pictures").FirstOrDefault(m => m.MenuId == id););
_dataContext.SaveChanges();
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Apr 30, 2010
How can i make my own delete method to prevent that the data really gets deleted? i want to set a datetime field when it gets deleted insted of a normal delete. i read about overriding the submitchanges function, but i don't get it to work
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Nov 22, 2010
How can i insert,update and delete records using entity framework data model.
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Dec 10, 2010
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Oct 28, 2010
I am busy developing an application using EF4 and MVC2. My development database has a few extra fields that is not in my production database. I have removed the fields from the Model, and published my application to my web server. But now I am getting errors that says I have some invalid column names, but I have removed it from my model. If I go to my Mapping Details, I see the fields removed from the Model are still there, but not mapped to anything.
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Dec 20, 2010
I ahve two tables each with a primary key. There is a lookup table in between the two tables with relationships. Below is a simplified look at the table structure
Table 'Product'
Column ProductPK int (Primary Key)
Table 'County'
Column CountyID int (primary key)
Table Product_County_Lookup
Column ProductPK int (Joint Primary Key)
Column CountyID int (joint primary key)
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Oct 6, 2010
i'm trying to use Entity Framework to insert into SQL SERVER 2005, using Visual studio 2008.the following codes are a Button onclick event,I want to insert into DB multiple rows at a time
[Code]....
however this does not work, it seems we can only insert into DB only one row at a time
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Sep 4, 2010
My setup is this; first I'm defining a couple of new rows.
newCompany = new company
companyInfo = value.company_info,
companyName = value.company_name,
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[code]...
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Oct 23, 2010
i have the following code where I want to retreive the data form a table using entity framework and put it to a list of the same type:
List<ItemDetail> iDets = new List<ItemDetail>();
iDets = (List<ItemDetail>) from l in db.ItemDetails
where l.ItemID == varItemID
select l;
when I run the page, it throws the following error:
Unable to cast object of type 'System.Data.Objects.ObjectQuery`1[LIBRIModel.ItemDetail]' to type 'System.Collections.Generic.List`1[LIBRIModel.ItemDetail]'.
why i'm having this problem? or am I missing something here if i'm not wrong it worked once, but now it throws this error
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Feb 14, 2011
I have a good friend who owns a print shop and he has asked me to create him a simple online shop where he can take print orders. His print shop location is kind of hidden, and business isn't going well at the moment. This is why he wants to move online. I said I would do it for him, but it will take a while before he has anything to look at. Where I am most stuck is the Model. The problem with this sorts of shops is that each Product, depending on its category would have different attributes. How ? Here is an example: [URL] A user would choose a product category, then he/she would get to the following: [URL] Now he/she would click the Order link to order a certain qunatity. On the next page, depending on what category they are in, they'll get a form where they can choose order attributes. There aren't many attribues for BUSINESS CARDS. But if they had chosen CARBONLESS FORMS, they would get options to tweak like: Squencial Numbering to start from 103490Position of Numbering..etc
I asked for advice at the SQL Server forums, and finally I came up with something like this:[URL] But with that database design, I will have a lot of type casting to do for the attributes ! << In fact I'm not sure if that would be even possible. Then I watched this video, and the author does something cool ! she uses Inheritance. Then I started Wonding ... Is it possible for me to have a Parent [ Product ] class, and have its children entities with different (added) attributes?
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Jan 19, 2011
I would like to have a short example on how do you actually perform relationships in Entity Framework 4 Code-First CTP 5 ?
Would love an example for these kind of relations :
* one-to-many
* many-to-many
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Apr 14, 2010
My requirement is to create an Enum based on values present in a table from DB. I am using ADO.NET Entity Framework model (.edmx file),
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Jan 24, 2011
ive tried to build some base project with above technologies. I wanted maximum flexibility and testability so i tried to use patterns along the way to make this as a base for future projects. However, it seem.something is wrong or whatever and i really need help here. So
i have two questions :1- Is there anything wrong with my current code ? Ive applied patterns correctly ?
2- Why do this code actually connect to the database, create it, but doesnt support insert even if i perform the corrects operation ? (Look at the end of the post for details about this error)
I have two entities : Comment and Review
COMMENT [Code]....
REVIEW[Code].... I built up a base repository for each of them this way :GENERIC REPOSITORY[Code]...For specific operations, i use an interface :[Code]....So i am getting the generics operations from the abstract class plus the specific operations :[Code]....As you figured out, i also use a database factory will produce the database context :DATABASE FACTORY [Code]....DISPOSABLE (Some extensions methods...)[Code]....DATABASE [Code]....And to finish, i have my unit of work....UNIT OF WORK[Code]....I also binded using Ninject the interfaces :NINJECT CONTROLLER FACTORY [Code]....however, when i call in the constructor ...[Code]....
This seem to create the database but doesnt't insert anything in the database in EF4. It seem that i may figured out the problem.. while looking at the database object.. the connection state is closed and server version throw an exception of this kind :
ServerVersion = '(((System.Data.Entity.DbContext (_database)).Database.Connection).ServerVersion' threw an exception of type 'System.InvalidOperationException'
I am doing the right things ? Is there anything wrong in what ive built ? Also if you have recommandation about the code i posted, i would be glad. I am just trying to the learn the right way for building any kind of application in MVC 3. I want a good a start.
I use :
- Entity Framework 4 Code-First CTP 5
- ASP.NET MVC 3
- Ninject as DI Container
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Oct 25, 2010
Is there a way to export a EF 4.0 Data Model to EF 3.5?
I looked around and found that we are not able to access EF 4.0 from a ASP.Net 3.5 project here: [URL]
Our project is the 1st to go to .Net 4.0 using Entity Framework and we (the team) were wondering if there was a way for the other projects that "might" need to access our data that are still using the .Net 3.5 framework.
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Jan 18, 2011
Im a fan of the EF code first and with its last preview of the CTP5 I wonder if it would be safe for me to use this for a smaller site for customer? I would love to get your opinions on this? And any good sources for tutorials and information would be sweet. I'm currently reading the post on scottgu's blog about it.
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Jan 3, 2011
I have the following classes:
public class Category
{
public int CategoryId { get; set; }
public string Name { get; set; }
}
public partial class CategoryMap : EntityTypeConfiguration<Category>
{
public CategoryMap()
{
this.HasKey(c => c.CategoryId);
this.Property(c => c.Name).IsRequired().HasMaxLength(400);
}
}
public class MyObjectContext : DbContext
{
public MyObjectContext(string connectionStringName)
: base(connectionStringName)
{
}
public DbSet<Category> Categories { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new CategoryMap());
base.OnModelCreating(modelBuilder);
}
}
Now when I run the following code I get an exception (GenericArguments[0], 'System.Int32', on 'System.Data.Entity.Internal.Linq.ReplacementDbQueryWrapper`1[TEntity]' violates the constraint of type 'TEntity')
DbDatabase.SetInitializer<MyObjectContext>(new DropCreateDatabaseIfModelChanges<MyObjectContext>());
using (var context = new MyObjectContext("NopSqlConnection"))
{
var query1 = from c in context.Categories
select c.CategoryId;
var test1 = query1.ToList(); //works fine
var query2 = from c in context.Categories
where query1.Contains(c.CategoryId)
orderby c.Name descending
select c;
var test2 = query2.ToList(); //throws the exception
}
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Sep 25, 2010
i have a web-site which uses forms based authentication. thus i have a login page with a login control on it. how would i go about coding the authenticate event of this control to talk to the Entity Framework to validate the user credentials?
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Aug 20, 2010
When I use classical ADO.NET or (which is interesting) EntityDataSource (e.g. for GridView), then page load within 1 second.But when I use ic codefile code like:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Cty = CType(Request.QueryString("cty"), Integer) ' course type
Page.SetFocus(ddl_FGPhotosOK)
If Not IsPostBack Then ' read course status
Using ctx_sdbEntities As New sdbEntities()
[code]...
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Feb 4, 2010
Using a very run-of-the-mill database, with identity int for primary keys, a Dynamic Data Entities Project (EntityFramework) displays the primary key for view and edit. When using Linq to Sql, the primary key fields are not displayed.
I would like to hide the primary keys and use Entity Framework (VS 2008, .Net 3.5 sp1).
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Jun 29, 2010
I'm working on a new project where I have the luxury of working from a Model to Database approach using Entity Framework 4.
The project I'm working on is taking an agile approach where different phases will be rolled out over time.
Will the Model First approach work in my case? I noticed when you "Generate Database from Model" it recreates the entire schema from scratch which will obviously wipe all the data that is in the db. I was hoping for a more "Update Database from Model" approach where the db would just be altered to reflect the changes rather than recreated
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Jan 18, 2010
I have three table like above, table C is mapping table which has foreign key of Table A and B.How can i select and insert data in Table C using Entity Frame Work?
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