I use entity-framework in my project i want to define and object that the user entry data
And finally insert the all data which user entry in database
But i need an object that hold the data before final insert(like dataset)
please advise me
I think it might be best that you have a further read of the entity framework. There are many examples, articles, threads, etc regarding EF4 and it's predecessors that should help you along your way.
To address what I think you mean by your question, you can take a look at using repository patterns. There are many variations, but here's a link to get you started:
http://blogs.microsoft.co.il/blogs/gilf/archive/2010/01/20/using-repository-pattern-with-entity-framework.aspx
I hope that helps.
Related
I'm very new to Core Data and I have two questions:
I want that all of my Patient entities have property bed which is a value of type bed... Can I create an entity for that too and connect always one patient with one bed?
I wondered if I can do something like every Patient has a property doctors, and that would be a array of doctors "[doctor]". How could I make this.
Thanks, hope you know what I mean, it would be great If someone knows how to do that.
Okay Larme and Joakim Danielson answers my question as comments under my post :)
Their comments:
Yes. The key word you are missing is "relations". You want relationship between your entities. Be it one to one, one to many, many to many. –
Find an online tutorial on learning and using Core Data, many of them handles entity relationships as well –
maybe on of you can help my with a little problem im dealing with right now.
I have a simple form with: Loginname, Loginpassword, Name, Firstname, Age. Now i want to save these information in two different tables. Users and UserInfo.
I have a model "user" that holds the login information. Now i want to save the additional data in the other database-table.
The user information is always linked to the normal user.
My thinking was, to store all the information in one big "user model" and upon $model->save() storing the data in the relating tables.
Especially when using the model in different modules it would be helpful to do all the magic in the model and not the controller.
Thanks in advance!
I think what you want todo is create a model mapper for handling your users data that will reference both your table models.
There is a good example here:
Multiple Tables for a single Model using Zend_Model_Mappers and Zend_Db_Table_Abstract
I have a requirement to only save data to a table in a database (I don't need to read it)
If the record already exists I want to update it otherwise I will add it.
It usually exists.
My entity context might already hold the object .. if it does I want to find it and use it again without causing it to refresh from the database when I 'find' it
i.e. The context holds a collection of entities (rows of a database) I want to find an entity in the collection and only want the context to go to the database if entity is not in the collection. I don't care about the current values of the entity .. I just want to update them.
Hope this is clear ..... thanks
I may not be quite seeing the question, but I believe your looking for some sort of caching mechanism, I know for work we use devForces IdeaBlade which does the trick, however I believe you can create a simple caching mechanism custom to you needs.
Link
The bits on caching will be helpful, if this doesnt help tell me and I can dig a little deeper.
I believe you need to use GetObjectByKey() instead of using an ObjectQuery I believe an ObjectQuery always hits the backend datastore whatever it may be.
More Info here http://msdn.microsoft.com/en-us/library/system.data.objects.objectcontext.getobjectbykey.aspx
I'm working on my first app using Core Data and I need to assign a type (with an associated name attribute) to a couple of entities.
Below is my object model so far.
The room and item types will be updated from time to time over the network.
Is this the best way to implement this using Core Data? Thanks :)
Edit: To try to explain better: for example, rooms may be Bedrooms, Kitchens etc. Items can be Aircon, Security Camera etc. The only difference between the different room and item types is the name text. The list of valid name texts will be updated so I don't want to hard code it in the app. Also, the user can create multiple rooms and items of the same type, which is why they are numbered (roomNumber,itemNumber)
improved Core Data Model Image http://img42.imageshack.us/img42/8458/picture6c.png
Nick, try and avoid the temptation of thinking of Core Data as a database. Design your model from the point of view looking at using the objects in your code.
i.e. your relationship properties are collections (or singluars) of the related thing.. you should rename the relationship JobLocation.JobLocationToRoom as just JobLocation.rooms
And yes, using Core Data will be quite straight forward, but it's hard to give you a definitive answer with such a vague question.
Perhaps my question wasn't clear, but I found the answer in the Apple iPhoneCoreDataRecipes demo code
The relationship I wanted to model is similar to Recipe -> RecipeType.
In addition to the other answers, you don't need to model separate ID attributes. Core Data managed objects automatically have managed object IDs that are handled for you entirely behind-the-scenes by the framework.
I'm working with a large hierarchical data set in sql server - modelled using the standard "EntityID, ParentID" kind of approach. There are about 25,000 nodes in the whole tree.
I often need to access subtrees of the tree, and then access related data that hangs off the nodes of the subtree. I built a data access layer a few years ago based on table-valued functions, using recursive queries to fetch an arbitrary subtree, given the root node of the subtree.
I'm thinking of using Entity Framework, but I can't see how to query hierarchical data like
this. AFAIK there is no recursive querying in Linq, and I can't expose a TVF in my entity data model.
Is the only solution to keep using stored procs? Has anyone else solved this?
Clarification: By 25,000 nodes in the tree I'm referring to the size of the hierarchical dataset, not to anything to do with objects or the Entity Framework.
It may the best to use a pattern called "Nested Set", which allows you to get an arbitrary subtree within one query. This is especially useful if the nodes aren't manipulated very often: Managing hierarchical data in MySQL.
In a perfect world the entity framework would provide possibilities to save and query data using this data pattern.
Everything IS possible with Entity Framework but you have to hack and slash your way in to it. The database I am currently working against has too many "holder tables" since Points for instance is shared with both teams and users. Both users and teams can also have a blog.
When you say 25 000 nodes do you mean navigational properties? If so I think it could be tricky to get the data access in place. It's not hard to navigate, search etc with entity framework but I tend to model on paper then create the database based on how I want to navigate while using entity framework. Sounds like you don't have that option.
Thanks for these suggestions.
I'm beginning to realise that the answer is to remodel the data in the database - either along the lines of nested sets as Georg suggests, or maybe a transitive closure table, which I've just come across.
That way, I'm hoping to get two key benefits:
a) faster querying aginst arbitrary subtrees
b) a data model which no longer requires recursive querying - so perhaps bringing it within easy reach of the Entity Framework!
It's always amazing how so often the right answer to a difficult problem is not to answer it, but to do something else instead!