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• Is it possible to use SqlGeography with Linq to Sql?

  - by cofiem

  I've been having quite a few problems trying to use Microsoft.SqlServer.Types.SqlGeography. I know full well that support for this in Ling to Sql is not great. I've tried numerous ways, beginning with what would the expected way (Database type of geography, CLR type of SqlGeography). This produces the NotSupportedException, which is widely discussed via blogs. I've then gone down the path of treating the geography column as a varbinary(max), as geography is a UDT stored as binary. This seems to work fine (with some binary reading and writing extension methods). However, I'm now running into a rather obscure issue, which does not seem to have happened to many other people. System.InvalidCastException: Unable to cast object of type 'Microsoft.SqlServer.Types.SqlGeography' to type 'System.Byte[]'. This error is thrown from an ObjectMaterializer when iterating through a query. It seems to only occur when the tables containing geography columns are included in a query implicitly (ie. using the EntityRef<> properties to do joins). System.Data.Linq.SqlClient.ObjectReaderCompiler.ObjectReader`2.MoveNext() My question: If I'm retrieving the geography column as varbinary(max), I might expect the reverse error: can't cast byte[] to SqlGeography. That I would understand. This I don't. I do have some properies on the partial LINQ to SQL classes that hide the binary conversion... could those be the issue? Any help appreciated, and I know there's probably not enough information.

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• Comparison operators not supported for type IList when Paging data in Linq to Sql

  - by Dan

  I can understand what the error is saying - it can't compare a list. Not a problem, other than the fact that I don't know how to not have it compare a list when I want to page through a model with a list as a property. My Model: Event : IEvent int Id string Title // Other stuff.. LazyList<EventDate> Dates // The "problem" property Method which pages the data (truncated): public JsonResult JsonEventList(int skip, int take) { var query = _eventService.GetEvents(); // Do some filtering, then page data.. query = query.Skip(skip).Take(take); return Json(query.ToArray()); } As I said, the above is truncated quite a bit, leaving only the main point of the function: filter, page and return JSON'd data. The exception occurs when I enumerate (.ToArray()). The Event object is really only used to list the common objects of all the event types (Meetings, Birthdays, etc - for example). It still implements IEvent like the other types, so I can't just remove the LazyList<EventDate> Dates' property unless I no longer implementIEvent` Anyway, is there a way to avoid this? I don't really want to compare a LazyList when I page, but I do not know how to resolve this issue. Thank you in advance! :)

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• general learning methodology

  - by momo

  just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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• Problem with Active Record

  - by kshchepelin

  Hello everyone. Lets assume we have a User model. And user can plan some activities. The number of types of activities is about 50. All activities have common properties, such as start_time, end_time, user_id, etc. But each of them has some unique properties. Now we have each activity living in its own table in DB. And thats why we have such terrible sql queries like SELECT * FROM `first_activities_table` WHERE (`first_activity`.`id` IN (17,18)) SELECT * FROM `second_activities_table` WHERE (`second_activity`.`id` = 17) ..... SELECT * FROM `n_activities_table` WHERE (`n_activity`.`id` = 44) About 50 queries. That's terrible. There are different ways to solve this. Choose the activity type with the biggest number of properties, create the table 'Activities' and have STI model. But this way we must name our columns in uncomfortable way and often the record in that table would have some NULL fields. Also STI model, but having columns, common for all of activity types and some blob column with serialized properties. But we have to do some search on activities - there can be a problem. And serialization is quite slow. Please help me dealing with this. Maybe my problem has quite different solution that will fit my needs. Thanks for help.

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• Generic callbacks

  - by bobobobo

  Extends So, I'm trying to learn template metaprogramming better and I figure this is a good exercise for it. I'm trying to write code that can callback a function with any number of arguments I like passed to it. // First function to call int add( int x, int y ) ; // Second function to call double square( double x ) ; // Third func to call void go() ; The callback creation code should look like: // Write a callback object that // will be executed after 42ms for "add" Callback<int, int, int> c1 ; c1.func = add ; c1.args.push_back( 2 ); // these are the 2 args c1.args.push_back( 5 ); // to pass to the "add" function // when it is called Callback<double, double> c2 ; c2.func = square ; c2.args.push_back( 52.2 ) ; What I'm thinking is, using template metaprogramming I want to be able to declare callbacks like, write a struct like this (please keep in mind this is VERY PSEUDOcode) <TEMPLATING ACTION <<ANY NUMBER OF TYPES GO HERE>> > struct Callback { double execTime ; // when to execute TYPE1 (*func)( TYPE2 a, TYPE3 b ) ; void* argList ; // a stored list of arguments // to plug in when it is time to call __func__ } ; So for when called with Callback<int, int, int> c1 ; You would automatically get constructed for you by < HARDCORE TEMPLATING ACTION > a struct like struct Callback { double execTime ; // when to execute int (*func)( int a, int b ) ; void* argList ; // this would still be void*, // but I somehow need to remember // the types of the args.. } ; Any pointers in the right direction to get started on writing this?

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• ASP.Net MVC: Showing the same data using different layouts...

  - by vdh_ant

  Hi guys I'm wanting to create a page that allows the users to select how they would like to view their data - i.e. summary (which supports grouping), grid (which supports grouping), table (which supports grouping), map, time line, xml, json etc. Now each layout would probably have different use a different view model, which inherit from a common base class/view model. The reason being that each layout needs the object structure that it deals with to be different (some need hierarchical others a flatter structure). Each layout would call the same repository method and each layout would support the same functionality, i.e. searching and filtering (hence these controls would be shared between layouts). The main exception to this would be sorting which only grid and table views would need to support. Now my question is given this what do people think is the best approach. Using DisplayFor to handle the rendering of the different types? Also how do I work this with the actions... I would imagine that I would use the one action, and pass in the layout types, but then how does this support the grouping required for the summary, grid and table views. Do i treat each grouping as just a layout type Also how would this work from a URL point of view - what do people think is the template to support this layout functionality Cheers Anthony

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• C# Fun with Generics - Mutual Dependencies

  - by Kenneth Cochran

  As an experiment I'm trying to write a generic MVP framework. I started with: public interface IPresenter<TView> where TView: IView<IPresenter<... { TView View { get; set;} } public interface IView<TPresenter> where TPresenter:IPresenter<IView<... { TPresenter Presenter { get; set; } } Obviously this can't work because the types of TView and TPresenter can't be resolved. You'd be writing Type<Type<... forever. So my next attempt looked like this: public interface IView<T> where T:IPresenter { ... } public interface IView:IView<IPresenter> { } public interface IPresenter<TView> where TView: IView { ... } public interface IPresenter: IPresenter<IView> { ... } This actually compiles and you can even inherit from these interfaces like so: public class MyView : IView, IView<MyPresenter> { ... } public class MyPresenter : IPresenter, IPresenter<MyView> { ... } The problem is in the class definition you have to define any members declared in the generic type twice. Not ideal but it still compiles. The problem's start creeping up when you actually try to access the members of a Presenter from a View or vice versa. You get an Ambiguous reference when you try to compile. Is there any way to avoid this double implementation of a member when you inherit from both interfaces? Is it even possible to resolve two mutually dependent generic types at compile time?

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• Prolog check if

  - by NickLee

  I'm creating a text adventure game on SWI-Prolog and I want to include (some kind of) dialogs. What I have so far is: dialog1(1):- nl,write('blah blah'),nl write('a: this is answer a'),nl, write('b: this is answer b'),nl. a:- write('respond to answer a'),nl. b:- write('respond to answer b'),nl. That's pretty much the first dialog. Now I want to create a second dialog similar to the first one. dialog1(2):- nl,write('blah blah'),nl, write('a: this is answer a'),nl, write('b: this is answer b'),nl. a:- write('respond to answer a'),nl. b:- write('respond to answer b'),nl. How can I check if the dialog is the first or the second one? I want to do that because when the user types a., I need the right answer a to be shown. I thought I could use something like a(1):- write('respond to answer a'),nl. b(1):- write('respond to answer b'),nl. /* and on the second dialog*/ a(2):- write('respond to answer a'),nl. b(2):- write('respond to answer b'),nl. But still, if the user is on dialog 2 and he types a(1),the first answer will appear.

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• Multiple queries using same datacontext throws SqlException

  - by Raj

  I've search control with which I'm trying to implement search as user types something. I'm using Linq to SQL to fire queries against the database. Though it works fine usually, when user types the queries really fast some random SqlException is thrown. These are the two different error message I stumbled across recently: A severe error occurred on the current command. The results, if any, should be discarded. Invalid attempt to call Read when reader is closed. Edit: Included code DataContextFactory class: public DataContextFactory(IConnectionStringFactory connectionStringFactory) { this.dataContext = new RegionDataContext(connectionStringFactory.ConnectionString); } public DataContext Context { get { return this.dataContext; } } public void SaveAll() { this.dataContext.SubmitChanges(); } Registering IDataContextFactory with Unity // Get connection string from Application.Current settings ConnectionInfo connectionInfo = Application.Current.Properties["ConnectionInfo"] as ConnectionInfo; // Register ConnectionStringFactory with Unity container as a Singleton this.container.RegisterType<IConnectionStringFactory, ConnectionStringFactory>(new ContainerControlledLifetimeManager(), new InjectionConstructor(connectionInfo.ConnectionString)); // Register DataContextFactory with Unity container this.container.RegisterType<IDataContextFactory, DataContextFactory>(); Connection string: Data Source=.\SQLEXPRESS2008;User Instance=true;Integrated Security=true;AttachDbFilename=C:\client.mdf;MultipleActiveResultSets=true; Using datacontext from a repository class: // IDataContextFactory dependency is injected by Unity public CompanyRepository(IDataContextFactory dataContextFactory) { this.dataContextFactory = dataContextFactory; } // return List<T> of companies var results = this.dataContextFactory.Context.GetTable<CompanyEntity>() .Join(this.dataContextFactory.Context.GetTable<RegionEntity>(), c => c.regioncode, r => r.regioncode, (c, r) => new { c = c, r = r }) .Where(t => t.c.summary_region != null) .Select(t => new { Id = t.c.compcode, Company = t.c.compname, Region = t.r.regionname }).ToList(); What is the work around?

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• WCF code generation for large/complex schema (HR-XML/OAGIS) - is there an alternative?

  - by Sasha Borodin

  Hello, and thank you for reading. I am implementing a WCF Service based on a predefined specification (HR-XML 3.0). As such, I am starting with the schema, and working my way back to code. There are a number of large Schema documents (which import yet more Schema documents) related to my implementation, provided by this specification. I am able to generate code using xsd.exe, by supplying the "main" and "supporting" xsd files as arguments. But there are several issues, and I am wondering if this is the right approach. there are litterally hundreds of classes - the code file is half a meg in size duplicate classes (ex. Type, Type1 - which both represent the same type) there are classes declared as inheriting from a base class, but that base class is not generated/defined I understand that there are limitations to the types of Schema supported by svcutil.exe/xsd.exe when targeting the DataContractSerializer and even XmlSerializer. My question is two-fold: Are code generation "issues" fairly common when dealing with larger, modular xsd files? Has anyone had success with generating data contracts from OAGIS or HR-XML schema? Given the above issues, are there better approaches to this task, avoiding generating code and working with concrete objects? Does it make better sence to read and compose a SOAP message directly, while still taking advantage of the rest of the WCF framework? I understand that I am loosing the convenience of working with .NET objects, and the framekwork-provided (de)serialization; given these losses, would it still be advantageous to base my Service on WCF? Is there some "middle ground" between working with .NET types and pure XML? Thank you very much! -Sasha Borodin DFWHC.org

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• Question about cloning in Java

  - by devoured elysium

  In Effective Java, the author states that: If a class implements Cloneable, Object's clone method returns a field-by-field copy of the object; otherwise it throws CloneNotSupportedException. What I'd like to know is what he means with field-by-field copy. Does it mean that if the class has X bytes in memory, it will just copy that piece of memory? If yes, then can I assume all value types of the original class will be copied to the new object? class Point { private int x; private int y; @Override public Point clone() { return (Point)super.clone(); } } If what Object.clone() does is a field by field copy of the Point class, I'd say that I wouldn't need to explicitly copy fields x and y, being that the code shown above will be more than enough to make a clone of the Point class. That is, the following bit of code is redundant: @Override public Point clone() { Point newObj = (Point)super.clone(); newObj.x = this.x; //redundant newObj.y = this.y; //redundant } Am I right? I know references of the cloned object will point automatically to where the original object's references pointed to, I'm just not sure what happens specifically with value types. If anyone could state clearly what Object.clone()'s algorithm specification is (in easy language) that'd be great. Thanks

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• What design pattern shall I use in this question?

  - by iyad al aqel

  To be frank, this is a homework question, so I'll tell you my opinion. Can you let me know my mistakes rather than giving me the solution? This is the question : Assume a restaurant that only offers the following two types of meals: (a) a full meal and (b)an economic meal. The full meal consists of the following food items and is served in the following order: 1. Appetizer 2. Drink 3. Main dish 4. Dessert Meanwhile the economic meal consists of the following food items and is served in the following order: 1. Drink 2. Main dish Identify the most appropriate design pattern that can be used to allow a customer to only order using one of the two types of meals provided and that the meal components must be served in the given order. I'm confused between the Factory and the Iterator and using them both together. Using the factory Pattern we can create the two meals full and economic and provide the user with with a base object class that will decide upon. But how can we enforce the ordering of the elements, I thought of using the iterator along that will iterate through the the composite of the two created factories sort of speak. What do you think?

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• Do COM Dll References Require Manual Disposal? If so, How?

  - by Drew

  I have written some code in VB that verifies that a particular port in the Windows Firewall is open, and opens one otherwise. The code uses references to three COM DLLs. I wrote a WindowsFirewall class, which Imports the primary namespace defined by the DLLs. Within members of the WindowsFirewall class I construct some of the types defined by the DLLs referenced. The following code isn't the entire class, but demonstrates what I am doing. Imports NetFwTypeLib Public Class WindowsFirewall Public Shared Function IsFirewallEnabled as Boolean Dim icfMgr As INetFwMgr icfMgr = CType(System.Activator.CreateInstance(Type.GetTypeFromProgID("HNetCfg.FwMgr")), INetFwMgr) Dim profile As INetFwProfile profile = icfMgr.LocalPolicy.CurrentProfile Dim fIsFirewallEnabled as Boolean fIsFirewallEnabled = profile.FirewallEnabled return fIsFirewallEnabled End Function End Class I do not reference COM DLLs very often. I have read that unmanaged code may not be cleaned up by the garbage collector and I would like to know how to make sure that I have not introduced any memory leaks. Please tell me (a) if I have introduced a memory leak, and (b) how I may clean it up. (My theory is that the icfMgr and profile objects do allocate memory that remains unreleased until after the application closes. I am hopeful that setting their references equal to nothing will mark them for garbage collection, since I can find no other way to dispose of them. Neither one implements IDisposable, and neither contains a Finalize method. I suspect they may not even be relevant here, and that both of those methods of releasing memory only apply to .Net types.)

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• Can I specify default value?

  - by atch

  Why is it that for user defined types when creating an array of objects every element of this array is initialized with default ctor but when I create built-in type this isn't the case? And second question: is it possible to specify default value to be used while initialize? Something like this (not valid): char* p = new char[size]('\0'); And another question in this topic while I'm with arrays. I suppose that when creating an array of user defined type and knowing the fact that every elem. of this array will be initialized with default value firstly why? If arrays for built in types do not initialize their elems. with their dflts why do they do it for UDT, and secondly: is there a way to switch it off/avoid/circumvent somehow? It seems like bit of a waste if I for example have created an array with size 10000 and then 10000 times dflt ctor will be invoked and I will (later on) overwrite this values anyway. I think that behaviour should be consistent, so either every type of array should be initialized or none. And I think that the behaviour for built-in arrays is more appropriate.

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• Conditionally Summing the same Column multiple times in a single select statement?

  - by btollett

  I have a single table that shows employee deployments, for various types of deployment, in a given location for each month: ID | Location_ID | Date | NumEmployees | DeploymentType_ID As an example, a few records might be: 1 | L1 | 12/2010 | 7 | 1 (=Permanent) 2 | L1 | 12/2010 | 2 | 2 (=Temp) 3 | L1 | 12/2010 | 1 | 3 (=Support) 4 | L1 | 01/2011 | 4 | 1 5 | L1 | 01/2011 | 2 | 2 6 | L1 | 01/2011 | 1 | 3 7 | L2 | 12/2010 | 6 | 1 8 | L2 | 01/2011 | 6 | 1 9 | L2 | 12/2010 | 3 | 2 What I need to do is sum the various types of people by date, such that the results look something like this: Date | Total Perm | Total Temp | Total Supp 12/2010 | 13 | 5 | 1 01/2011 | 10 | 2 | 1 Currently, I've created a separate query for each deployment type that looks like this: SELECT Date, SUM(NumEmployees) AS "Total Permanent" FROM tblDeployment WHERE DeploymentType_ID=1 GROUP BY Date; We'll call that query qSumPermDeployments. Then, I'm using a couple of joins to combine the queries: SELECT qSumPermDeployments.Date, qSumPermDeployments.["Total Permanent"] AS "Permanent" qSumTempDeployments.["Total Temp"] AS "Temp" qSumSupportDeployments.["Total Support"] AS Support FROM (qSumPermDeployments LEFT JOIN qSumTempDeployments ON qSumPermDeployments.Date = qSumTempDeployments.Date) LEFT JOIN qSumSupportDeployments ON qSumPermDeployments.Date = qSumSupportDeployments.Date; Note that I'm currently constructing that final query under the assumption that a location will only have temp or support employees if they also have permanent employees. Thus, I can create the joins using the permanent employee results as the base table. Given all of the data I currently have, that assumption holds up, but ideally I'd like to move away from that assumption. So finally, my question. Is there a way to simplify this down to a single query or is it best to separate it out into multiple queries - if for no other reason that readability.

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• How can you pre-define a variable that will contain an anonymous type?

  - by HitLikeAHammer

  In the simplified example below I want to define result before it is assinged. The linq queries below return lists of anonymous types. result will come out of the linq queries as an IEnumerable<'a but I can't define it that way at the top of the method. Is what I am trying to do possible (in .NET 4)? bool large = true; var result = new IEnumerable(); //This is wrong List<int> numbers = new int[]{1,2,3,4,5,6,7,8,9,10}.ToList<int>(); if (large) { result = from n in numbers where n > 5 select new { value = n }; } else { result = from n in numbers where n < 5 select new { value = n }; } foreach (var num in result) { Console.WriteLine(num.value); } EDIT: To be clear I know that I do not need anonymous types in the example above. It is just to illustrate my question with a small, simple example.

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• Redirecting to frontpage after 404 error in PHP

  - by Saif Bechan

  I have a php web page that now uses custom error pages when a page is not found. The custom error pages are included in PHP. So when somebody types in an URL that does not exists I just include an error page, and the error page starts with: <?php header("HTTP/1.1 404 Not> Found"); ?> This also tells crawlers that the page does not exist. Now I have set up a new system. When a user types a wrong url, the user is sent back to the frontpage and a message is displayed on the frontpage. I redirect to the frontpage like this: header('Location:' . __TINY_URL . '/'); Now the problem is PHP just sends back a 200 code, page found. How can I mix these two to create a 404 code on the frontpage. And is this overall a nice way of presenting and error page.

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• How to setup relationships in contact Database

  - by Walt

  I am currently embarking on a new venture to learn PHP and MySQL. I have done some simple databases in the past using Access, but this one is to be a web-centric database for tracking a myriad of data including contacts and project information. I will need to link the various tables in various relationships, and I am not sure the best way to do that. Since I am just starting out with PHP/MySQL I am researching online sources for learning as much as possible. If anyone has recommendations on books or websites, I would appreciate it. In setting up my tables, one major area that I am concerned with is contacts. I will have a variety of contacts that include: employees, clients, vendors, subcontractors, etc.. and a single contact can be multiple types and each type would have various additional fields that pertain to them. My thought was to have one contacts table that links to other tables for the various contact types. I'm not sure which field type or setup of table options are best... Thoughts? This scenario will likely play out in other areas of the database as well for projects and products. Any pointers/direction would be appreciated. WES

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• Applying fine-grained security to an existing application

  - by Mark

  I've inherited a reasonably large and complex ASP.NET MVC3 web application using EF Code First on SQL Server. It uses ASP.NET Membership roles with database authentication. The controller actions are secured with attributes derived from AuthorizeAttribute that map roles to actions. There are extension methods for the finer points, such as showing a particular widget to particular roles. This is works great and I have a good understanding of the current security model. I've been asked to provide finer grained security at the data level. For example a 'Customer' user can only see data (throughout the database) associated with themselves and not other Customers. The problem is that 'Customer' is only 1 of 5 different types with their own specific restrictions (each of the 9 roles is one of these 5 types). The best thing I can think of is to go through all the data repositories and extend each and every LINQ statements/query with a filter for every user type. Even if I had time for that it doesn't seem like the most elegant way. Any suggestions? I really don't know where to start with this so anything could be helpful. Many thanks.

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• Pass Linq Expression to a function

  - by Kushan Hasithe Fernando

  I want to pass a property list of a class to a function. with in the function based on property list I'm going to generate a query. As exactly same functionality in Linq Select method. Here I'm gonna implement this for Ingress Database. As an example, in front end I wanna run a select as this, My Entity Class is like this public class Customer { [System.Data.Linq.Mapping.ColumnAttribute(Name="Id",IsPrimaryKey=true)] public string Id { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Name")] public string Name { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Address")] public string Address { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Email")] public string Email { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Mobile")] public string Mobile { get; set; } } I wanna call a Select function like this, var result = dataAccessService.Select<Customer>(C=>C.Name,C.Address); then,using result I can get the Name and Address properties' values. I think my Select function should looks like this, ( *I think this should done using Linq Expression. But im not sure what are the input parameter and return type. * ) Class DataAccessService { // I'm not sure about this return type and input types, generic types. public TResult Select<TSource,TResult>(Expression<Func<TSource,TResult>> selector) { // Here using the property list, // I can get the ColumnAttribute name value and I can generate a select query. } } This is a attempt to create a functionality like in Linq. But im not an expert in Linq Expressions. There is a project call DbLinq from MIT, but its a big project and still i couldn't grab anything helpful from that. Can someone please help me to start this, or can someone link me some useful resources to read about this.

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• Using an ORM with a database that has no defined relationships?

  - by Ahmad

  Consider a database(MSSQL 2005) that consists of 100+ tables which have primary keys defined to a certain degree. There are 'relationships' between tables, however these are not enforced with foreign key constraints. Consider the following simplified example of typical types of tables I am dealing with. The are clear relations between the User and City and Province tables. However, they key issues is the inconsistent data types in the tables and naming conventions. User: UserRowId [int] PK Name [varchar(50)] CityId [smallint] ProvinceRowId [bigint] City: CityRowId [bigint] PK CityDescription [varchar(100)] Province: ProvinceId [int] PK ProvinceDesc [varchar(50)] I am considering a rewrite of the application (in ASP.net MVC) that uses this data source as is similar in design to MVC storefront. However I am going through a proof of concept phase and this is one of the stumbling blocks I have come across. What are my options in terms of ORM choice that can be easily used and why? Should I even be considering an ORM? (The reason I ask this is that most explanations and tutorials all work with relatively cleanly designed existing databases, or newly created ones when compared to mine. I am thus having a very hard time trying to find a way forward with this problem) There is a huge amount of existing SQL queries, would a datamappper(eg IBatis.net) be more suitable since we could easily modify them to work and reuse the investment already made? I have found this question on SO which indicates to me that an ORM can be used - however I get the impression that this a question of mapping? Note: at the moment, the object model is not clearly defined as it was non-existent. The existing system pretty much did almost everything in SQL or consisted of overly complicated, and numerous queries to complete fucntionality. I am pretty much a noob and have zero experience around ORMs and MVC - so this an awesome learning curve I am on.

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• Encapsulating user input of data for a class (C++)

  - by Dr. Monkey

  For an assignment I've made a simple C++ program that uses a superclass (Student) and two subclasses (CourseStudent and ResearchStudent) to store a list of students and print out their details, with different details shown for the two different types of students (using overriding of the display() method from Student). My question is about how the program collects input from the user of things like the student name, ID number, unit and fee information (for a course student) and research information (for research students): My implementation has the prompting for user input and the collecting of that input handled within the classes themselves. The reasoning behind this was that each class knows what kind of input it needs, so it makes sense to me to have it know how to ask for it (given an ostream through which to ask and an istream to collect the input from). My lecturer says that the prompting and input should all be handled in the main program, which seems to me somewhat messier, and would make it trickier to extend the program to handle different types of students. I am considering, as a compromise, to make a helper class that handles the prompting and collection of user input for each type of Student, which could then be called on by the main program. The advantage of this would be that the student classes don't have as much in them (so they're cleaner), but also they can be bundled with the helper classes if the input functionality is required. This also means more classes of Student could be added without having to make major changes to the main program, as long as helper classes are provided for these new classes. Also the helper class could be swapped for an alternative language version without having to make any changes to the class itself. What are the major advantages and disadvantages of the three different options for user input (fully encapsulated, helper class or in the main program)?

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• Boost's "cstdint" Usage

  - by patt0h

  Boost's C99 stdint implementation is awfully handy. One thing bugs me, though. They dump all of their typedefs into the boost namespace. This leaves me with three choices when using this facility: Use "using namespace boost" Use "using boost::[u]<type><width>_t" Explicitly refer to the target type with the boost:: prefix; e.g., boost::uint32_t foo = 0; Option ? 1 kind of defeats the point of namespaces. Even if used within local scope (e.g., within a function), things like function arguments still have to be prefixed like option ? 3. Option ? 2 is better, but there are a bunch of these types, so it can get noisy. Option ? 3 adds an extreme level of noise; the boost:: prefix is often = to the length of the type in question. My question is: What would be the most elegant way to bring all of these types into the global namespace? Should I just write a wrapper around boost/cstdint.hpp that utilizes option ? 2 and be done with it? Also, wrapping the header like so didn't work on VC++ 10 (problems with standard library headers): namespace Foo { #include <boost/cstdint.hpp> using namespace boost; } using namespace Foo; Even if it did work, I guess it would cause ambiguity problems with the ::boost namespace.

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• C two functions in one with casts

  - by Favolas

  I have two functions that do the exact same thing but in two different types of struct and this two types of struct are very similar. Imagine I have this two structs. typedef struct nodeOne{ Date *date; struct nodeOne *next; struct nodeOne *prev; }NodeOne; typedef struct nodeTwo{ Date *date; struct nodeTwo *next; struct nodeTwo *prev; }NodeTwo; Since my function to destroy each of the list is almost the same (Just the type of the arguments are different) I would like to make just one function to make the two thins. I have this two functions void destroyListOne(NodeOne **head, NodeOne **tail){ NodeOne *aux; while (*head != NULL){ aux = *head; *head = (*head)->next; free(aux); } *tail = NULL; } and this one: void destroyListTwo(NodeTwo **head, NodeTwo **tail){ NodeTwo *aux; while (*head != NULL){ aux = *head; *head = (*head)->next; free(aux); } *tail = NULL; } Since they are very similar I thought making something like this: void destroyList(void **ini, void **end, int listType){ if (listType == 0) { NodeOne *aux; NodeOne head = (NodeOne) ini; NodeOne tail = (NodeOne) ed; } else { NodeTwo *aux; NodeTwo head = (NodeTwo) ini; NodeTwo tail = (NodeTwo) ed; } while (*head != NULL){ aux = *head; *head = (*head)->next; free(aux); } *tail = NULL; } As you may now this is not working but I want to know if this is possible to achieve. I must maintain both of the structs as they are.

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• How do actually castings work at the CLR level?

  - by devoured elysium

  When doing an upcast or downcast, what does really happen behind the scenes? I had the idea that when doing something as: string myString = "abc"; object myObject = myString; string myStringBack = (string)myObject; the cast in the last line would have as only purpose tell the compiler we are safe we are not doing anything wrong. So, I had the idea that actually no casting code would be embedded in the code itself. It seems I was wrong: .maxstack 1 .locals init ( [0] string myString, [1] object myObject, [2] string myStringBack) L_0000: nop L_0001: ldstr "abc" L_0006: stloc.0 L_0007: ldloc.0 L_0008: stloc.1 L_0009: ldloc.1 L_000a: castclass string L_000f: stloc.2 L_0010: ret Why does the CLR need something like castclass string? There are two possible implementations for a downcast: You require a castclass something. When you get to the line of code that does an castclass, the CLR tries to make the cast. But then, what would happen had I ommited the castclass string line and tried to run the code? You don't require a castclass. As all reference types have a similar internal structure, if you try to use a string on an Form instance, it will throw an exception of wrong usage (because it detects a Form is not a string or any of its subtypes). Also, is the following statamente from C# 4.0 in a Nutshell correct? Upcasting and downcasting between compatible reference types performs reference conversions: a new reference is created that points to the same object. Does it really create a new reference? I thought it'd be the same reference, only stored in a different type of variable. Thanks

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