Entity Framework 4 - Check If Navigation Property Collection Is Empty, Without Include() Or Load()?
Sep 28, 2010
In an MVC view, I'm looking for a way to determine if a parent entity's collection of child entities is empty, so I can decide if I need to call a RenderPartial() or not.
For a one-to-one I've been using the following:
<% if (Model.Book.GenreReference.EntityKey != null) %>
{.....}
but I'm unsure how to do it in a one-to-many scenario, or if it can even be done without the use of Include() or Load().
View 2 Replies
Similar Messages:
Feb 2, 2011
I use EF 4 and C #.
I need populate a Pure Junction Table (containing only FK to other tables) when an EntityDataSource _Inserted event is raised.
I have 3 Tables in my Database:
[code]....
Here a useful resource:
But I am not able to implment it:
[code]....
View 1 Replies
Apr 22, 2010
I have a question, much liket this unanswered one. I'm trying to work with the entity framework, and having a tough time getting my foreign tables to update. I have something basically like this in the DB:
Incident (table):
-ID
-other fields
Responses (table):
-FK:Incident.ID
-other fields
And and entities that match:
Incident (entity)
-ID
-Other fields
-Responses (EntityCollection of Responses via navigation property)
Each Incident can have 0 or more responses.
In my Webpage, I have a form to allow the user to enter all the details of an Incident, including a list of responses. I can add everything to the database when a new Incident is created, however I'm having difficulty with editing the Incident.
When the page loads for edit, I populate the form and then store the responses in the viewstate. When the user changes the list of responses (adds one, deletes one or edits one). I store this back into the viewstate. Then when the user clicks the save button, I'd like to save the changes to the Incident and the Responses back to the DB. I cannot figure out how to get the responses from the detached viewstate into the Incident object so that they can be updated together.
Currently when the user clicks save, I'm getting the Incident to edit from the db, making changes to the Incident's fields and then saving it back to the DB. However I can't figure out how to have the detached list of responses from the viewstate attach to the Incident. I have tried the following without success:
Clearning the Incident.Responses collection and adding the ones from the viewstate back in:
Incident.Responses.Clear()
for each objResponse in Viewstate("Responses")
Incident.Responses.add(objResponse)
next
Creating an EntityCollection from my list and then assiging that to the Incident.Responses
Incident.Responses = EntityCollectionFromViewstateList
Iterating through the responses in Incident.Response and assigning the corresponding object from viewstate:
for each ObjResponse in Incident.Responses
objResponse = objCorrespondingModifedResonseFromViewState
Next
These all fail, I'd like to be able to merge the changes into the Inicdent object so that when the BLL calls SaveChanges on the changes to both the Incident and Responses will happen at the same time.
View 1 Replies
Sep 24, 2010
I am trying to do something like this:
[Code]....
But ofcourse it is not working as I want to. The Ordering works on Question.Order, but I would also the
Questions.SubQuestions List to be ordered according to SubQuestions.Order
View 2 Replies
Feb 28, 2011
I'm using EntityDataSource to retrieve my items, and i want to get the items for a particular region. (items and regions has a many to many relationship, thus item has a regions navigation property). and I'm using "IN" to filter the items. tried several combinations and it kept on throwing various errors. how can i get this sorted out:
Below is My DataSource:
[code]....
View 1 Replies
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.
View 1 Replies
Mar 8, 2011
I'm Using Entity Framework in my ASP.NET Web Application and I added Procedure tom my Model and Create Function for it which will return ObjectResult ... i want to add Include Keyword to that object Result ... so how can i get childs for that object result
View 2 Replies
Mar 4, 2010
I have two Entity classes: Order and OrderItem. Order contains a navigation property OrderItemSet of type
System.Data.Objects.DataClasses.EntityCollection<OrderItem>
On an aspx page is a FormView bound to this EntityDataSource:
[code]....
When I run the application I get an exception pointing to the line DataSource='<%# Eval("OrderItemSet")%>' in markup and telling me:
DataBinding: System.Web.UI.WebControls.EntityDataSourceWrapper does not contain a property with name 'OrderItemSet'
What is wrong here?
View 1 Replies
Dec 10, 2010
I want to write a query in Entity Framework that has multiple joins. The only problem is the tables arn't related using their primary / foreign keys (its the Umbraco database), as such I can't use .Include and the Navigation properties.
Essentially the query I would like to run is this:
select t.*, n.* from cmsContentType t
inner join cmsContentTypeAllowedContentType a on t.nodeId = a.Id
inner join vicinity.DocumentTypeExtendedProperty x on x.UmbracoDocumentTypeId = t.pk
inner join umbracoNode n on n.id = t.nodeId
I have two EF entities mapped to cmsContentType and umbracoNode as such I would like them to be populated as if I was running the query like
var q = from p in cmsContentType.Include("umbracoNode")
View 4 Replies
Sep 29, 2010
I'm using Entity Framework 4 for a simple app and would like to bake my connection credentials into the following connection string:
<connectionStrings>
<add name="MyEntities"
connectionString="metadata=res://*/MyDataModel.csdl|res://*/MyDataModel.ssdl|res://*/MyDataModel.msl;provider=System.Data.SqlClient;provider connection string="Data Source=localhostDEV;Initial Catalog=MyDB;UserId=myUser;Password=jack&jill;MultipleActiveResultSets=True""
providerName="System.Data.EntityClient" />
</connectionStrings>
However, the password (which I cannot change) contains an ampersand. ASP.NET throws:
Configuration Error: An error occurred while parsing EntityName. Line XX, position YYY.
If I replace the ampersand in the password with &, I get a SqlException: Login failed for user 'myUser'. Usually this trick works, but I'm guessing that something is failing because this is technically a connection string inside a connection string.
What should I do here? Most of my classes include code like:
using (var context = new MyEntities()) {
// do work
}
Update: It turns out that the credentials I am using are a domain account, so what I really need is Integrated Security=True in the connection string rather than a password.
Encoding the ampersand as indicated in the accepted answer should work fine, though I haven't tested it.
View 3 Replies
Mar 28, 2011
I've got a GridView on a ASP.Net page. I would like to set the DataSource of the Gridview to a trackable collection of Entity Framework objects. I though the code should look like this:
this.gvMyGridView.DataSource = entity.MyDetailedItems;
this.gvMyGridView.DataBind();
But this doesn't display any data.
I am using self tracking entities and the MyDetailedItems is a navigation property to rows from another table.
View 2 Replies
Feb 28, 2011
I'm trying to have a View where the user can add items in a collection without having to go to a new View (the scenario is a sort of CV site where the user adds info about work experience, skills, etc, and it would seem absurd to go to a new View to add each little thing).
So I have an edit View that shows a number of text boxes for the already added items, and there's an ajax call to go to a method to fetch the collection fresh if the user adds an item.
Here are the methods in question:
[code]....
View 1 Replies
Aug 6, 2010
I'm new to LINQ and EF and I seem to be having trouble working this out.
I have a many-to-many relationship between my Location and Region tables. When adding or editing a Location, my interface allows the user to check any number of related Regions. If they click OK, I need to add any new relationships that were checked, and delete any existing relationships that have been unchecked. My basic code is shown below.
However, this code doesn't work. Lower down, the line location.Regions.Contains(region) returns false even when the location already is related to the region. The issue appears to be because the region is from my populated listbox that was initialized earlier and is no longer part of the current EF context. But if I try and add it, I get an error that there is already a Region with that ID.
It seems like what I want to do is change this line to something like location.Regions.Contains((r) => r.RgnID == region.RgnID) so I'm only testing for a particular ID. But this gives me the error "Cannot convert lambda expression to type 'TrailCalendar.Region' because it is not a delegate type."
I don't understand this error but, either way, I'm not sure how I can test if the relationship already exists without reloading a bunch of data, which I'd like to avoid.
View 1 Replies
Feb 20, 2011
I want to be able to update a model and all its collections of child objects in the same view. I have been referred to these examples: http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx and http://blog.stevensanderson.com/2010/01/28/editing-a-variable-length-list-aspnet-mvc-2-style/ .
For example, I have an object Consultant, that has a collection of "WorkExperiences". All this is in an Entity Framework model. In the view, the simple properties of the Consultant object is no problem, but the collection I cannot get a textbox to show up for. I tried following the examples in the links above, but it doesn't work. The problem is, in those examples the model is just a list (not an object with a child list property). And also, the model again is an EF model. And for some reason that doesn't seem to work as in those examples.
[Code]....
This stuff with the EditorTemplate works fine in Phil Haack's sample project, which I downloaded to try, but here, with the EF model or whatever the problem is, I don't get any textbox at all. The table in the view is just there as a test, because in the table I do get the rows for WorkExperiences, whether I add an empty WorkExperience object or fill out its properties doesn't matter, the rows show up for each object. But again, no textbox...
View 2 Replies
Oct 19, 2010
I am using the Entity Framework for the first time and want to know if the following is possible - I have generated my classes from the DB, and have one called Category.
Obviously it has all my fields in the table (ID, CategoryName, SortOrder etc..) but I want to know if I can add a custom property which is not in the table, but is actually the result of a custom method.
I want to add a new property called 'CategoryURL' which is basically the 'CategoryName' property run through a custom method and returns a hyphenated string.
My initial thought is inheriting from the generated Category class and creating something like this inside?
public string CategoryURL
{
get{ return MyCustomMethod(this.CategoryName) }
}
Is this the correct approach? And will 'this.CategoryName' work as I think it should? Basically the end result is when I return a list of 'Category' I want this to be part of the class so I can use it in my foreach loop.
View 1 Replies
Apr 8, 2010
How to make this method return boolean value, depending on query return. False - nothing, True - data exists. Before i just returned int from uniqueQuote.Count() but does not look like great method.
private bool CheckEnquiryUser(int enquiryId, Guid userId)
{
int selectedEnquiryId = enquiryId;
[code]...
View 3 Replies
May 29, 2010
I need to check if any rows are returned in a QueryString here's what I have so far.not sure what code to put to see if the row count is greater than 1
private void BindDataToGrid()
{
//MessageBoardEntities3 is ThemeableAttribute connection string name
int TID = Convert.ToInt32(Request.QueryString["ThreadID"].ToString()); // if Post ID is int
var context = new MessageBoardEntities3();
gvPosts.DataSource = from p in context.Posts
where p.ThreadID == TID
select new { p.Post1, p.PostID };
gvPosts.DataBind();
lblNoPosts.Text = "No posts found for this thread.";
}
View 1 Replies
May 3, 2010
I developed and entity framework (.edmx) application in 4.0 in that i got all the data of my querying table and its foreign key referenced tables data also. but when i change my project to 3.5 i am unable to get the data of foreign key referenced tables data.
View 2 Replies
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.
View 1 Replies
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.
View 1 Replies
Jun 30, 2010
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?
View 1 Replies
Aug 10, 2010
What is the best way to include repeating content on every page of a website such as a navigation menu?
View 2 Replies
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>();
}................................
View 9 Replies
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.
View 2 Replies
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]....
View 1 Replies
