C# - NULL Values In Object Properties In Entity Framework?
Feb 12, 2010
Tables: Article, Author, Comment (1 article and 1 author can have * comments)In the database is 1 article, 1 author and 1 comment.
The problem is, that code
myBD my_bd = new myBD();
var articles = by_bd.Article;
works OK, I can see that an Author and an Article has 1 comment. But that code
var comm = (from u in my_bd.Comment
where ......
select u);
returns the comment but it has NULL values in property Article and Author. Why ?
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Oct 1, 2010
I've been learning MVC 2 and I have pretty much everything understood except for the model part of things, I understand what the model is but actually implementing it has me confused.
Here's my situation, I have my DB which has 3 tables;
Ideas - table of ideas
Tags - table of tags
IdeaTag - link table connecting the above 2 tables via FKs
So when using the Entity Framework (.edmx) designer in VS2010 I get 2 classes created in the Designer, which obviously map to my DB tables and Navigation Properties in Idea for Tags & Idea for Tag.
So this is all fine until I actually try to add tags to an idea, what's the best practise for dealing with Navigation Properties? I wanted to add a Textbox which will then map to the Tags property in the Idea class but I'm unsure how I'd go about this.
Most of the MVC tutorials which discuss EF or Linq to SQL are quite basic.
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Jan 21, 2010
When I run the code below, it works
int charId = int.Parse(Request.Params["charId"]);
EveFPT ctx = new EveFPT();
var theCharQuery = from a in ctx.tblChars
where a.id == charId
select new
{
Name = a.name,
CorpName = a.tblCorps.name,
AllianceName = a.tblCorps.tblAlliances.name
};
if(theCharQuery.Count() == 1)
{
var theChar = theCharQuery.First();
lblCharName.Text = theChar.Name;
lblCorpName.Text = theChar.CorpName;
lblAllianceName.Text = theChar.AllianceName;
}
However, If I the below
var theCharQuery = from a in ctx.tblChars
where a.id == charId
select a;
if(theCharQuery.Count() == 1)
{
tblChars theChar = theCharQuery.First();
lblCharName.Text = theChar.name;
lblCorpName.Text = theChar.tblCorps.name;
lblAllianceName.Text = theChar.tblCorps.tblAlliances.name;
}
the statement theChar.tblCorps always returns null.
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Feb 24, 2010
I'm using the linq to entity command to perform a record update. I want to set one of the fields back to NULL but I'm not sure how do it. I have a query such as
Dim record = From r in db.LISTS where r.ID = refID Select r
record.Title = txtTitle.text
if txtDetail.text = "" then
record.Detail =
end if
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Apr 1, 2011
I have to change the username column in my database to nullable, which means everywhere in my code, I now have to check username.HasValue and change references to username to username.Value. Is there anything I can do to avoid having to change all the references to username to username.Value?
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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
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return _dataContext.Menu.Include("ChildMenu").Include("ParentMenu").Include("Pictures").FirstOrDefault(m => m.MenuId == id);
//then i loop all child objects
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//foreach (var item in menu.Pictures)
for (int i = 0; i < picList.Count; i++)
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// dm.Picture.Delete(picList[i].Id);
//menu.Pictures.de
//_dataContext.SaveChanges();
//picList[i] = null;
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_dataContext.DeleteObject(_dataContext.Menu.Include("ChildMenu").Include("ParentMenu").Include("Pictures").FirstOrDefault(m => m.MenuId == id););
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Nov 14, 2010
I'm trying to figure out how to bind an EF4.0 object to my textbox control. I have a call to my business object that returns an entity CFUser that has a FirstName parameter on it of type string. However, after I make the call and bind the object, the codebehind executes which fills the BindUser property with the correct value. However, nothing shows up in the textbox.
my aspx side is
[Code]....
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Oct 8, 2010
I have a sql server table with a date column that has a default value of GetDate()
this default does not seem to get passed to the EF and so i was wondering what the most elegant way was to code this default value within my asp.net application? I dont want to manually alter the EF Model as i may want to re-import it and dont want to lose these changes.
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Feb 5, 2010
I am using logger to record all error information.
When log error informtion we need to
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Jan 21, 2011
So, have a search form where users can enter one or more keywords, these keywords are then held in a List<string> called keywords. Now using Entity Framework have an Organisation entity with a Name field. What I want to do is select those organisations whose name contains all the keywords. I don't care if they are in the right order or not but it just contain all the keywords. Also organsiations is a big table in the database so I don't want to materialise all the organsiation objects on the server and then loop through them. So what I'm looking for (excuse my LINQ naivety here) is equivalent to the non-existent LINQ statement:
[Code]....
I'm sure this must have already been answered but just can't find it.
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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 28, 2011
I'm working on an application that uses an approach to localization where they just call a translate function for every piece of text on a page. It leads to a lot of redundant code that looks like this (psuedocode):
function page_load():
translateControlText(control1, language);
translateControlText(control2, language);
translateControlText(control3, language);
translateControlText(control4, language);
translateControlText(control5, language);
translateControlText(control6, language);
translateImageAlt(image1, language);
100 more lines of this on a single page
The application is massive, so I don't have the opportunity to rewrite the translation logic. However, I think I could just loop through all of the controls on a page, check their type, and translate the appropriate property. At least then I would just have to call 1 function per page, and then throw it in a base page or master. However, I probably wouldn't want to translate certain things, such as table cells. Regardless, there is an attribute called Localizable that is on many properties such as Control.Text and Image.Alt. I'd like to be able to get a list of every string on the Page that is stored in a Property marked Localizable. Is this possible? Is this possible without reflection?
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Feb 5, 2010
I've sucefully created a method to insert values through EF, but i've a question (maybe, a newbie question).
Should i send the values to be inserted as strings to the DAL, and then i create the object there or should i create the object in View Layer and then send him to DAL?
Example 1 (DAL):
[Code]....
Example 1 (View Layer, on a click button for example):
[Code]....
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Then i create the object cdcModel.noticias and set the fields there with the strings values.
What do you advice me to do? I know that both ways works, but i'm trying to develope with better patterns (i don't know if this is the exacly word, sorry my bad english)
cdcModel.noticias campos = new cdcModel.noticias();
campos.tituloPT = "a";
campos.tituloEN = "b";
campos.descricaoPT = "a";
campos.descricaoEN = "a";
if (DAL.NoticiasInsert(campos)
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Oct 25, 2010
Is there a way to export a EF 4.0 Data Model to EF 3.5?
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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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Oct 13, 2010
We have an ASP.NET MVC site that uses Entity Framework abstractions with Repository and UnitOfWork patterns. What I'm wondering is how others have implemented navigation of complex object graphs with these patterns. Let me give an example from one of our controllers:
[code]....
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Aug 24, 2010
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Nov 2, 2010
I am new to entity framework , it is really very good , but I want to know what is the difference between using entity framework with stored procedure or without stored procedure , which one the faster and what is the benefits for using stored procedures with entity framework.
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I have an EDM, it includes the entities extension and history. My goal is to use history to keep track of all the changes made to extension entity. For example, if extension with ID 223 has its property 'Name_Display' changed - I want the history entity to record this.
I'm using ASP.NET with VB.NET. Where in my code do I put the hook to say, "update the history entity" and what should that hook look like?
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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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Feb 10, 2011
I am mapping a stored procedure to an entity by right clicking on the entity (in the .edmx) and selecting "Stored Procedure Mapping." This brings you to a Mapping Details - "Name of Entity" Window that allows you to select the insert, update, and delete stored procedures associated with the Entity. It also maps the stored procedure parameter to the Entity "Property" (Column).
I'm gettin an error "error 2042: Parameter Mapping specified is not valid." The cause of the error is fairly obvious, in the Insert stored procedure that has been selected, a 'CHAR' parameter is being mapped to an Int32 Entity Property. I altered the stored procedure parameter to match the entity, I deleted the stored procedure, readded, and reslected it as the Insert function. I also cleaned, validated, updated model from database. No matter what I do, the parameter list in the mapping details doesn't reflect the change to the stored procedure. It's stuck on a char --> int32 mapping, even though it has been changed, like it's buried deep in meta data some where.
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Aug 5, 2010
I am trying to add a new entity and have to refernce associated data to add it. I cannot load the Referencetables. Giving "The EntityReference could not be loaded because it is not attached to an ObjectContext." How do i complete this task in Entity Framework 3.5
[Code]....
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Mar 31, 2011
I have a stupid problem with the Entity Framework. I get the following Exception:
[Code]....
I have an entity with a 4 fields representing the primary key. I copy it via serialization (works fine). I set the old entity to not valid (Datefield set to a date in the past, this field is part of the PK) and set the copied entity to DateTime.Now.Date. When I call context.AddObject I get the Exception above. I tried copying the entity via reflection but the entity has 3-4 references. And when copied, I get another Exception before even Adding the entity to the context. I also tried setting newObj.EntityKey = null and reset all the fields neccessary for the PK. I just want a whole copy of an entity with a different primary key (and some other fields changed too) and Create it in the database.
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Sep 21, 2010
I'm writing a custom .NET MembershipProvider (not the built in one) and trying to update using Entity Framework. But of course i have no access to (Try)UpdateModel. How can i update it?
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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:
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Feb 3, 2011
Here's a simple code snippet where I create a new Entity object and call SaveChanges() to create a new record in the mapped database table.
[Code]....
What I'm trying to figure out is whether there is a way to derive this new key for my entity, e, from the ObjectContext, m? The reason for this is that the way my actual code is structured, my entity object is already out of scope at the point where I call the SaveChanges() method.
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