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  • How should I provide access to this custom DAL?

    - by Casey
    I'm writing a custom DAL (VB.NET) for an ordering system project. I'd like to explain how it is coded now, and receive some alternate ideas to make coding against the DAL easier/more readable. The DAL is part of an n-tier (not n-layer) application, where each tier is in it's own assembly/DLL. The DAL consists of several classes that have specific behavior. For instance, there is an Order class that is responsible for retrieving and saving orders. Most of the classes have only two methods, a "Get" and a "Save," with multiple overloads for each. These classes are marked as Friend and are only visible to the DAL (which is in it's own assembly). In most cases, the DAL returns what I will call a "Data Object." This object is a class that contains only data and validation, and is located in a common assembly that both the BLL and DAL can read. To provide public access to the DAL, I currently have a static (module) class that has many shared members. A simplified version looks something like this: Public Class DAL Private Sub New End Sub Public Shared Function GetOrder(OrderID as String) as OrderData Dim OrderGetter as New OrderClass Return OrderGetter.GetOrder(OrderID) End Function End Class Friend Class OrderClass Friend Function GetOrder(OrderID as string) as OrderData End Function End Class The BLL would call for an order like this: DAL.GetOrder("123456") As you can imagine, this gets cumbersome very quickly. I'm mainly interested in structuring access to the DAL so that Intellisense is very intuitive. As it stands now, there are too many methods/functions in the DAL class with similar names. One idea I had is to break down the DAL into nested classes: Public Class DAL Private Sub New End Sub Public Class Orders Private Sub New End Sub Public Shared Function Get(OrderID as string) as OrderData End Function End Class End Class So the BLL would call like this: DAL.Orders.Get("12345") This cleans it up a bit, but it leaves a lot of classes that only have references to other classes, which I don't like for some reason. Without resorting to passing DB specific instructions (like where clauses) from BLL to DAL, what is the best or most common practice for providing a single point of access for the DAL?

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  • How sophisticated should be DAL?

    - by Andrew Florko
    Basically, DAL (Data Access Layer) should provide simple CRUD (Create/Read/Update/Delete) methods but I always have a temptation to create more sophisticated methods in order to minimize database access roundtrips from Business Logic Layer. What do you think about following extensions to CRUD (most of them are OK I suppose): Read: GetById, GetByName, GetPaged, GetByFilter... e.t.c. methods Create: GetOrCreate methods (model entity is returned from DB or created if not found and returned), Create(lots-of-relations) instead of Create and multiple AssignTo methods calls Update: Merge methods (entities list are updated, created and deleted in one call) Delete: Delete(bool children) - optional children delete, Cleanup methods Where do you usually implement Entity Cache capabilities? DAL or BLL? (My choice is BLL, but I have seen DAL implementations also) Where is the boundary when you decide: this operation is too specific so I should implement it in Business Logic Layer as DAL multiple calls? I often found insufficient BLL operations that were implemented in dozen database roundtrips because developer was afraid to create a bit more sophisticated DAL. Thank you in advance!

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  • .net, C# Interface between Business Logic and DAL

    - by Joel
    I'm working on a small application from scratch and using it to try to teach myself architecture and design concepts. It's a .NET 3.5, WPF application, and I'm using Sql Compact Edition as my data store. I'm working on the business logic layer, and have just now begun to write the DAL. I'm just using SqlCeComamnds to send over simple queries and SqlCeResultSet to get at the results. I'm starting to design my Insert and Update methods, and here's the issue - I don't know the best way to get the necessary data from the BLL into the DAL. Do I pass in a generic collection? Do I have a massive parameter list with all the data for the database? Do I simply pass in the actual business object (thus tying my DAL to the conrete stuff in the BLL?). I thought about using interfaces - simply passing IBusinessObjectA into the DAL, which provides the simplicity I'm looking for without tying me TOO tightly to current implementations. What do you guys think?

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  • Empty data problem - data layer or DAL?

    - by luckyluke
    I designing the new App now and giving the following question a lot of thought. I consume a lot of data from the warehouse, and the entities have a lot of dictionary based values (currency, country, tax-whatever data) - dimensions. I cannot be assured though that there won't be nulls. So I am thinking: create an empty value in each of teh dictionaries with special keyID - ie. -1 do the ETL (ssis) do the correct stuff and insert -1 where it needs to let the DAL know that -1 is special (Static const whatever thing) don't care in the code to check for nullness of dictionary entries because THEY will always have a value But maybe I should be thinking: import data AS IS let the DAL do the thinking using empty record Pattern still don't care in the code because business layer will have what it needs from DAL. I think is more of a approach thing but maybe i am missing something important here... What do You think? Am i clear? Please don't confuse it with empty record problem. I do use emptyCustomer think all the time and other defaults too.

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  • DAL Layer : EF 4.0 or Normal Data access layer with Stored Procedure

    - by Harryboy
    Hello Experts, Application : I am working on one mid-large size application which will be used as a product, we need to decide on our DAL layer. Application UI is in Silverlight and DAL layer is going to be behind service layer. We are also moving ahead with domain model, so our DB tables and domain classes are not having same structure. So patterns like Data Mapper and Repository will definitely come into picture. I need to design DAL Layer considering below mentioned factors in priority manner Speed of Development with above average performance Maintenance Future support and stability of the technology Performance Limitation : 1) As we need to strictly go ahead with microsoft, we can not use NHibernate or any other ORM except EF 4.0 2) We can use any code generation tool (Should be Open source or very cheap) but it should only generate code in .Net, so there would not be any licensing issue on per copy basis. Questions I read so many articles about EF 4.0, on outset it looks like that it is still lacking in features from NHibernate but it is considerably better then EF 1.0 So, Do you people feel that we should go ahead with EF 4.0 or we should stick to ADO .Net and use any code geneartion tool like code smith or any other you feel best Also i need to answer questions like what time it will take to port application from EF 4.0 to ADO .Net if in future we stuck up with EF 4.0 for some features or we are having serious performance issue. In reverse case if we go ahead and choose ADO .Net then what time it will take to swith to EF 4.0 Lastly..as i was going through the article i found the code only approach (with POCO classes) seems to be best suited for our requirement as switching is really easy from one technology to other. Please share your thoughts on the same and please guide on the above questions

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  • Decoupling into DAL and BLL - my concerns.

    - by novice_man
    Hi, In many posts concerning this topic I come across very simple examples that do not answer my question. Let's say a have a document table and user table. In DAL written in ADO.NET i have a method to retries all documents for some criteria. Now I the UI I have a case where I need to show this list along with the names of the creator. Up to know I have it done with one method in DAL containig JOIN statement. However eveytime I have such a complex method i have to do custom mapping to some object that doesn't mark 1:1 to DB. Should it be put into another layer ? If so then I will have to resing from join query for iteration through results and querying each document author. . . which doen't make sense... (performance) what is the best approach for such scenarios ?

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  • Generate A Simple Read-Only DAL?

    - by David
    I've been looking around for a simple solution to this, trying my best to lean towards something like NHibernate, but so far everything I've found seems to be trying to solve a slightly different problem. Here's what I'm looking at in my current project: We have an IBM iSeries database as a primary repository for a third party software suite used for our core business (a financial institution). Part of what my team does is write applications that report on or key off of a lot of this data in some way. In the past, we've been manually creating ADO .NET connections (we're using .NET 3.5 and Visual Studio 2008, by the way) and manually writing queries, etc. Moving forward, I'd like to simplify the process of getting data from there for the development team. Rather than creating connections and queries and all that each time, I'd much rather a developer be able to simply do something like this: var something = (from t in TableName select t); And, ideally, they'd just get some IQueryable or IEnumerable of generated entities. This would be done inside a new domain core that I'm building where these entities would live and the applications would interface with it through a request/response service layer. A few things to note are: The entities that correspond to the database tables should be generated once and we'd prefer to manually keep them updated over time. That is, if columns/tables are added to the database then we shouldn't have to do anything. (If some are deleted, of course, it will break, but that's fine.) But if we need to use a new column, we should be able to just add it to the necessary class(es) without having to re-gen the whole thing. The whole thing should be SELECT-only. We're not doing a full DAL here because we don't want to be able to break anything in the database (even accidentally). We don't need any kind of mapping between our domain objects and the generated entity types. The domain barely covers a fraction of the data that's in there, most of it we'll never need, and we would rather just create re-usable maps manually over time. I already have a logical separation for the DAL where my "repository" classes return domain objects, I'm just looking for a better alternative to manual ADO to be used inside the repository classes. Any suggestions? It seems like what I'm doing is just enough outside the normal demand for DAL/ORM tools/tutorials online that I haven't been able to find anything. Or maybe I'm just overlooking something obvious?

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  • C# Design How to Elegantly wrap a DAL class

    - by guazz
    I have an application which uses MyGeneration's dOODads ORM to generate it's Data Access Layer. dOODad works by generating a persistance class for each table in the database. It works like so: // Load and Save Employees emps = new Employees(); if(emps.LoadByPrimaryKey(42)) { emps.LastName = "Just Got Married"; emps.Save(); } // Add a new record Employees emps = new Employees(); emps.AddNew(); emps.FirstName = "Mr."; emps.LastName = "dOOdad"; emps.Save(); // After save the identity column is already here for me. int i = emps.EmployeeID; // Dynamic Query - All Employees with 'A' in thier last name Employees emps = new Employees(); emps.Where.LastName.Value = "%A%"; emps.Where.LastName.Operator = WhereParameter.Operand.Like; emps.Query.Load(); For the above example(i.e. Employees DAL object) I would like to know what is the best method/technique to abstract some of the implementation details on my classes. I don't believe that an Employee class should have Employees(the DAL) specifics in its methods - or perhaps this is acceptable? Is it possible to implement some form of repository pattern? Bear in mind that this is a high volume, perfomacne critical application. Thanks, j

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  • How to use bll, dal and model?

    - by bruno
    Dear all, In my company I must use a Bll, Dal and model layer for creating applications with a database. I've learned at school that every databasetable should be an object in my model. so I create the whole model of my database. Also I've learned that for every table (or model object) there should be a DAO created into the DAL. So I do this to. Now i'm stuck with the BLL classes. I can write a BLLclass for each DAO/ModelObject or I can write a BLLclass that combine some (logic) DAO's... Or i can write just one Bllclass that will manage everything. (this last one I'm sure it aint the best way..) What is the best practice to handle this Bll 'problem'? And a second question. If a bll is in need of tablecontent from an other table where it aint responsible for, whats the best way to get the content? Go ask on the responsible BLL or go directly to the DAO? I'm struggling with these questions the last 2 months, and i don't know what is the best way to handle it.

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  • PHP 5: What DAL are you using?

    - by overthetop
    hello I'm new to PHP and I recently started learning Zend Framework. What DAL are you using? Do you think that Zend_Db_* can do the magic? I need it mainly for MySql db. Does it have any limitations and can I use it in big project without any problems because I don't want to go the wrong way. 10x

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  • DAL, Session, Cache architecture

    - by subt13
    I'm attempting to create Data Access Layer for my web application. Currently, all datatables are stored in the session. When I am finished the DAL will populate and return datatables. Is it a good idea to store the returned datatables in the session? A distributed/shared cache? Or just ping the database each time? Note: generally the number of rows in the datatable will be small < 2000. Thanks

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  • DAL without web2py

    - by Jay
    I am using web2py to power my web site. I decided to use the web2py DAL for a long running program that runs behind the site. This program does not seem to update its data or the database (sometimes). from gluon.sql import * from gluon.sql import SQLDB from locdb import * # contains # db = SQLDB("mysql://user/pw@localhost/mydb", pool_size=10) # db.define_table('orders', Field('status', 'integer'), Field('item', 'string'), # migrate='orders.table') orderid = 20 # there is row with id == 20 in table orders #when I do db(db.orders.id==orderid).update(status=6703) db.commit() It does not update the database, and a select on orders with this id, shows the correct data. In some circumstances a "db.rollback()" after a commit seems to help. Very strange to say the least. Have you seen this, more importantly do you know the solution? Jay

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  • Adeus ano bom – bem vindo, melhor ainda.

    - by anobre
    Olá pessoal! Este ano de 2010 foi realmente muito bom. A NBR cresceu consideravelmente, eu tive algumas mudanças no meu trabalho, me casei, comprei um apartamento e tudo mais. Definitivamente, este ano ficará marcado para sempre. Fiz diversos amigos, dentro da comunidade Microsoft também. O melhor ainda é que as perspectivas para 2011 são ainda mais positivas. E pelo que estou vendo, este sentimento é comum a muitos amigos por aí, o que me deixa mais feliz ainda. Sem mais, desejo a todos um feliz ano de 2011, que muitos objetivos e conquistas sejam alcançados. Indepentende de tecnologias, linguagens ou religiões, que cada um faça o seu melhor, para garantir o melhor a sua volta. Espero que todos sigam duas palavras: MUDANÇAS e EMPREENDEDORISMO. Um forte abraço a todos e até ano que vem!

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  • DAL Exception handling in a MVP application

    - by Chathuranga
    In a MVP win forms application I'm handling exceptions as follows in DAL. Since the user messaging is not a responsibility of DAL, I want to move it in to my Presentation class. Could you show me a standard way to do that? public bool InsertAccount(IBankAccount ba) { string selectStatement = @"IF NOT EXISTS (SELECT ac_no FROM BankAccount WHERE ac_no=@ac_no) BEGIN INSERT INTO BankAccount ..."; using (SqlConnection sqlConnection = new SqlConnection(db.ConnectionString)) { using (SqlCommand sqlCommand = new SqlCommand(selectStatement, sqlConnection)) { try { sqlConnection.Open(); sqlCommand.Parameters.Add("@ac_no", SqlDbType.Char).Value = ba.AccountNumber; // // sqlCommand.ExecuteNonQuery(); return true; } catch (Exception e) { MessageBox.Show(("Error: " + e.Message)); } if (sqlConnection.State == System.Data.ConnectionState.Open) sqlConnection.Close(); return false; } } }

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  • .NET DAL and arhitecture

    - by Parhs
    I have seen lots of articles but none really help me. That is because I want to use dapper as a DAL. Should I create repositories with special functions? Like getStaffActive()? If I use repositories I can implement with dapper-extension a generic crud I have no idea how to handle database connection. Where to open the connection? If I do this at every function then how am I supposed to use transaction scope? Somehow the repositories I work with should share a connection in order transaction to work. But how to do this? Openning connection in BLL? If I use queries and execute them directly then still the same thing.

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  • project with 2 types of interfaces performing different jobs, should they use the same BLL and DAL?

    - by user2080257
    i am working on a project that has two interface (web and desktop), they are not performing the same tasks but they use the same BLL and DAL, the web part using 100% of the BLL and DAL, while the desktop only needs to know about 20% of the BLL and DAL. do you think it is a good idea to let the desktop use the same BLL and DAL as the web, which consequently will lead to ditributing thos BLL and DAL with the desktop application? or you think i'd better create new BLL and DAL projects just to serve the desktop app? but in this case i will fall in the trap of maintaining two copies of the same code!

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  • .NET How would I build a DAL to meet my requirments?

    - by Jonno
    Assuming that I must deploy an asp.net app over the following 3 servers: 1) DB - not public 2) 'middle' - not public 3) Web server - public I am not allowed to connect from the web server to the DB directly. I must pass through 'middle' - this is purely to slow down an attacker if they breached the web server. All db access is via stored procedures. No table access. I simply want to provide the web server with a ado dataset (I know many will dislike this, but this is the requirement). Using asmx web services - it works, but XML serialisation is slow and it's an extra set of code to maintain and deploy. Using a ssh/vpn tunnel so that the one connects to the db 'via' the middle server, seems to remove any possible benefit of maintaining 'middle'. Using WCF binary/tcp removes the XML problem, but still there is extra code. Is there an approach that provides the ease of ssh/vpn, but the potential benefit of having the dal on the middle server? Many thanks.

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  • Should I return IEnumerable<T> or IQueryable<T> from my DAL?

    - by Gary '-'
    I know this could be opinion, but I'm looking for best practices. As I understand, IQueryable implements IEnumerable, so in my DAL, I currently have method signatures like the following: IEnumerable<Product> GetProducts(); IEnumerable<Product> GetProductsByCategory(int cateogoryId); Product GetProduct(int productId); Should I be using IQueryable here? What are the pros and cons of either approach? Note that I am planning on using the Repository pattern so I will have a class like so: public class ProductRepository { DBDataContext db = new DBDataContext(<!-- connection string -->); public IEnumerable<Product> GetProductsNew(int daysOld) { return db.GetProducts() .Where(p => p.AddedDateTime > DateTime.Now.AddDays(-daysOld )); } } Should I change my IEnumerable<T> to IQueryable<T>? What advantages/disadvantages are there to one or the other?

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  • Writing a Data Access Layer (DAL) for SQL Server

    In this tip, I am going to show you how you can create a Data Access Layer (to store, retrieve and manage data in relational database) in ADO .NET. I will show how you can make it data provider independent, so that you don't have to re-write your data access layer if the data storage source changes and also you can reuse it in other applications that you develop. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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  • Is a Multi-DAL Approach the way to go here?

    - by Krisc
    Working on the data access / model layer in this little MVC2 project and trying to think things out to future projects. I have a database with some basic tables and I have classes in the model layer that represent them. I obviously need something to connect the two. The easiest is to provide some sort of 'provider' that can run operations on the database and return objects. But this is for a website that would potentially be used "a lot" (I know, very general) so I want to cache results from the data layer and keep the cache updated as new data is generated. This question deals with how best to approach this problem of dual DALS. One that returns cached data when possible and goes to the data layer when there is a cache miss. But more importantly, how to integrate the core provider (thing that goes into database) with the caching layer so that it too can rely on cached objects rather than creating new ones. Right now I have the following interfaces: IDataProvider is used to reach the database. It doesn't concern itself with the meaning of the objects it produces, but simply the way to produce them. interface IDataProvider{ // Select, Update, Create, et cetera access IEnumerable<Entry> GetEntries(); Entry GetEntryById(int id); } IDataManager is a layer that sits on top of the IDataProvider layer and manages the cache interface IDataManager : IDataProvider{ void ClearCache(); } Note that in practice the IDataManager implementation will have useful helper functions to add objects to their related cache stores. (In the future I may define other functions on the interface) I guess what I am looking for is the best way to approach a loop back from the IDataProvider implementations so that they can access the cache. Or a different approach entirely may be in order? I am not very interested in 3rd party products at the moment as I am interested in the design of these things much more than this specific implementation. Edit: I realize the title may be a bit misleading. I apologize for that... not sure what to call this question.

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  • Should DAL always return business objects in MVP

    - by Chathuranga
    In Model View Presenter (MVP) pattern, it is said that our DAL always should returns business models. But let's say if I want to get just a number from database like the last ClientID (the latest clients ID) which is a string, should my DAL method returns a ClientInfo object which has about 10 other fields as well like ClientName, Address etc.? If I want to get a list of business objects from my DAL, is it acceptable to do it as follows or better to get a DataTable from DAL and then in the applications BLL, converts it a List? public List<Employee> GetNewEmployees() { string selectStatement = "SELECT Employee.Emp_ID, Employee.Initials + ' ' + Employee.Surname AS Name,..."; using (SqlConnection sqlConnection = new SqlConnection(db.GetConnectionString)) { using (SqlCommand sqlCommand = new SqlCommand(selectStatement, sqlConnection)) { sqlConnection.Open(); using (SqlDataReader dataReader = sqlCommand.ExecuteReader()) { List<Employee> list = new List<Employee>(); while (dataReader.Read()) { list.Add ( new EpfEtfMaster { EmployeeID = (int) dataReader ["emp_id"], EmployeeName = (string) dataReader ["Name"], AppointmentDate = (DateTime) dataReader["appointment_date"], }); } return list; } } } }

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  • Return type from DAL class (Sql ce, Linq to Sql)

    - by bretddog
    Hi, Using VS2008 and Sql CE 3.5, and preferably Linq to Sql. I'm learning database, and unsure about DAL methods return types and how/where to map the data over to my business objects: I don't want direct UI binding. A business object class UserData, and a class UserDataList (Inherits List(Of UserData)), is represented in the database by the table "Users". I use SQL Compact and run SqlMetal which creates dbml/designer.vb file. This gives me a class with a TableAttribute: <Table()> _ Partial Public Class Users I'm unsure how to use this class. Should my business object know about this class, such that the DAL can return the type Users, or List(Of Users) ? So for example the "UserDataService Class" is a part of the DAL, and would have for example the functions GetAll and GetById. Will this be correct : ? Public Class UserDataService Public Function GetAll() As List(Of Users) Dim ctx As New MyDB(connection) Dim q As List(Of Users) = From n In ctx.Users Select n Return q End Function Public Function GetById(ByVal id As Integer) As Users Dim ctx As New MyDB(connection) Dim q As Users = (From n In ctx.Users Where n.UserID = id Select n).Single Return q End Function And then, would I perhaps have a method, say in the UserDataList class, like: Public Class UserDataList Inherits List(Of UserData) Public Sub LoadFromDatabase() Me.clear() Dim database as New UserDataService dim users as List(Of Users) users = database.GetAll() For each u in users dim newUser as new UserData newUser.Id = u.Id newUser.Name = u.Name Me.Add(newUser) Next End Sub End Class Is this a sensible approach? Would appreciate any suggestions/alternatives, as this is my first attempt on a database DAL. cheers!

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  • Sync Framework, Local Database Cache, and my DAL

    - by Refracted Paladin
    I am creating a WPF app that needs to allow users to work in a temporary disconnected state and I plan to use a Local Database Cache. My question's are about my data access layer. Do you typically create the whole DAL to point at the Cache or both and create a switching mechanism? Is Entity's a good way to go for my DAL against the Cache? I am used to L2S but my understanding is that I can't use that against SQLCE, correct? Thanks! PS: Any good resources out there for using Sync, Linq, and WPF? Tutorials, videos, etc?

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  • Sync Framework,LINQ, and my DAL

    - by Refracted Paladin
    I am creating a WPF app that needs to allow users to work in a temporary disconnected state and I plan to use a Local Database Cache. My question's are about my data access layer. Do you typically create the whole DAL to point at the Cache or both and create a switching mechanism? Is Entity's a good way to go for my DAL against the Cache? I am used to L2S but my understanding is that I can't use that against SQLCE, correct? Thanks! PS: Any good resources out there for using Sync, Linq, and WPF ALL TOGETHER? Tutorials, videos, etc?

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  • Proper way to structure a Sync Framework DAL

    - by Refracted Paladin
    I am creating a WPF app that needs to allow users to work in a temporary disconnected state and I plan to use a Local Database Cache. My question's are about my data access layer. Do you typically create the whole DAL to point at the Cache or both and create a switching mechanism? Is Entity's a good way to go for my DAL against the Cache? I am used to L2S but my understanding is that I can't use that against SQLCE, correct? Thanks! PS: Any good resources out there for using Sync, Linq, and WPF ALL TOGETHER? Tutorials, videos, etc?

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