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  • Type-safe generic data structures in plain-old C?

    - by Bradford Larsen
    I have done far more C++ programming than "plain old C" programming. One thing I sorely miss when programming in plain C is type-safe generic data structures, which are provided in C++ via templates. For sake of concreteness, consider a generic singly linked list. In C++, it is a simple matter to define your own template class, and then instantiate it for the types you need. In C, I can think of a few ways of implementing a generic singly linked list: Write the linked list type(s) and supporting procedures once, using void pointers to go around the type system. Write preprocessor macros taking the necessary type names, etc, to generate a type-specific version of the data structure and supporting procedures. Use a more sophisticated, stand-alone tool to generate the code for the types you need. I don't like option 1, as it is subverts the type system, and would likely have worse performance than a specialized type-specific implementation. Using a uniform representation of the data structure for all types, and casting to/from void pointers, so far as I can see, necessitates an indirection that would be avoided by an implementation specialized for the element type. Option 2 doesn't require any extra tools, but it feels somewhat clunky, and could give bad compiler errors when used improperly. Option 3 could give better compiler error messages than option 2, as the specialized data structure code would reside in expanded form that could be opened in an editor and inspected by the programmer (as opposed to code generated by preprocessor macros). However, this option is the most heavyweight, a sort of "poor-man's templates". I have used this approach before, using a simple sed script to specialize a "templated" version of some C code. I would like to program my future "low-level" projects in C rather than C++, but have been frightened by the thought of rewriting common data structures for each specific type. What experience do people have with this issue? Are there good libraries of generic data structures and algorithms in C that do not go with Option 1 (i.e. casting to and from void pointers, which sacrifices type safety and adds a level of indirection)?

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  • Wait window in a windows application

    - by Vinodtiru
    I basically need to show a wait window to the user. For this i have put two seperate window forms in the application. the first form is the main form with a button. The second one is a empty one with just a label text. On click of the button in Form1 i do the below Form2 f = new Form2(); f.Show(); Thread.Sleep(2000); f.Close(); My idea here is to show the wait window to the user for 2 second. But when i do this the Form 2 is not completely loaded because of which the label in it is blank. Please let me know your inputs on this.

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  • Not all Code Paths return a Value Issue

    - by jorame
    I have this peace of code in a class(DataBase) and I'm getting "Not all Paths return a Value". Any help will be really appreciated. public static DataSet DELETE_PDT(String rowid) { SqlConnection con = new SqlConnection(); SqlCommand cmd = new SqlCommand("sp_DELETE_PDT", con); cmd.CommandType = CommandType.StoredProcedure; cmd.Parameters.Add("@rowid", SqlDbType.Int).Value = rowid; con.ConnectionString = ConfigurationManager.ConnectionStrings["WMS"].ConnectionString; try { con.Open(); cmd.ExecuteNonQuery(); cmd.Dispose(); con.Close(); } catch (Exception ex) { throw new Exception("Error while deleting record. Please contact your System Administrator", ex); } }

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  • Generic Dictionary - Getting Convertion Error

    - by pm_2
    The following code is giving me an error: // GetDirectoryList() returns Dictionary<string, DirectoryInfo> Dictionary<string, DirectoryInfo> myDirectoryList = GetDirectoryList(); // The following line gives a compile error foreach (Dictionary<string, DirectoryInfo> eachItem in myDirectoryList) The error it gives is as follows: Cannot convert type 'System.Collections.Generic.KeyValuePair<string,System.IO.DirectoryInfo>' to 'System.Collections.Generic.Dictionary<string,System.IO.DirectoryInfo>’ My question is: why is it trying to perform this conversion? Can I not use a foreach loop on this type of object?

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  • Html.ActionLink in a button

    - by Pomster
    I Am trying to connect to a method in my controller, with a button. I can connect though this link: @Html.ActionLink("Print", "Print", new { id = Model.SalesContractId}) But i Don't want a link, i want my button on my dialog to do it. I have tried the following: $('#btnDialogPrint').click(function () { location.href = '<%= Url.Action("Print", "Print", new { id = Model.SalesContractId}) %>'; }); But it just redirect me to a page that say bad request. namespace Contract.Controllers { public class ContractController : Controller { CompassEntities db = new CompassEntities(); public ActionResult Print(int id) { return View(""); // This can be removed and Print code may be added } Don't worry about the code inside i will get to that once i get inside this method. Could i maybe attach a link here? <input type="button" value="Print" id="btnDialogPrint" />

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  • How to override [Authorize] attribute in the MVC Web API?

    - by NullReference
    I have a MVC Web Api Controller that uses the [Authorize] attribute at the class level. This makes all of the api methods require authorization but I'd like to create an attribute called [ApiPublic] that overrides the [Authorize] attribute. There is a similar technique described here for normal MVC controllers. I tried creating an AuthorizeAttribute based of the System.Web.Http.AuthorizeAttribute but none of the overridden events are called if I put it on a api method that has the [Authorize] at the class level. Anyone have an idea how to override the authorize for the web api? [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)] public class ApiPublicAttribute : AuthorizeAttribute { protected override void HandleUnauthorizedRequest(System.Web.Http.Controllers.HttpActionContext actionContext) { base.HandleUnauthorizedRequest(actionContext); } public override void OnAuthorization(System.Web.Http.Controllers.HttpActionContext actionContext) { base.OnAuthorization(actionContext); } protected override bool IsAuthorized(System.Web.Http.Controllers.HttpActionContext actionContext) { return true; } }

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  • Bind web user control property in markup

    - by Ian Levy
    I'm sure it's elementary but I can't figure it out. This does not work - the the binding expression is passed as string to the control: {<uc:usercontrol runtat="server" message='<%#Me.protectedVariable%>'/>} The code behind include a Page.Databind() call in page_load. But this does work: <uc:usercontrol runat="server" id="usercontrol1"/> And in code behind page_load: usercontrol1.message = Me.protectedVariable Do I have to bind from the code-behind? Is this a page life cycle issue?

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  • Validation is not working

    - by Joby Kurian
    hi...I have one asp content page.Its contain many controls like dropdownlist,textbox etc.All controls are inside a div tag.I gave required field validator for all my drop down list.i have one SAVE button that reside inside another div tag.I gave SAVE button cause validation true.But my problem is that, the validator is not working and the page.Isvalid property is true.What is the problem with my code?

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  • scala 2.8 CanBuildFrom

    - by oxbow_lakes
    Following on from another question I asked, I wanted to understand a bit more about the Scala method TraversableLike[A].map whose signature is as follows: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That Notice a few things about this method: it takes a function turning each A in the traversable into a B it returns That and takes an implicit argument of type CanBuildFrom[Repr, B, That] I can call this as follows: > val s: Set[Int] = List("Paris", "London").map(_.length) s: Set[Int] Set(5,6) What I cannot quite grasp is how the fact that That is bound to B (i.e. it is some collection of B's) is being enforced by the compiler. The type parameters look to be independent in both the signature above and in the signature of the trait CanBuildFrom itself: trait CanBuildFrom[-From, -Elem, +To] How is the scala compiler ensuring that That cannot be forced into something which does not make sense? > val s: Set[String] = List("Paris", "London").map(_.length) //will not compile EDIT - this question of course boils down to: How does the compiler decide what implicit CanBuildFrom objects are in scope for the call?

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  • Passing the Class<T> in java of a generic list?

    - by Rob Stevenson-Leggett
    I have a method for reading JSON from a service, I'm using Gson to do my serialization and have written the following method using type parameters. public T getDeserializedJSON(Class<T> aClass,String url) { Reader r = getJSONDataAsReader(url); Gson gson = new Gson(); return gson.fromJson(r, aClass); } I'm consuming json which returns just an array of a type e.g. [ { "prop":"value" } { "prop":"value" } ] I have a java class which maps to this object let's call it MyClass. However to use my method I need to do this: RestClient<ArrayList<MyClass>> restClient = new RestClient<ArrayList<MyClass>>(); ArrayList<MyClass> results = restClient.getDeserializedJSON(ArrayList<MyClass>.class, url); However, I can't figure out the syntax to do it. Passing just ArrayList.class doesn't work. So is there a way I can get rid of the Class parameter or how do I get the class of the ArrayList of MyClass?

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  • Two references to the same domain/entity model

    - by Sbossb
    Problem I want to save the attributes of a model that have changed when a user edits them. Here's what I want to do ... Retrieve edited view model Get domain model and map back updated value Call the update method on repository Get the "old" domain model and compare values of the fields Store the changed values (in JSON) into a table However I am having trouble with step number 4. It seems that the Entity Framework doesn't want to hit the database again to get the model with the old values. It just returns the same entity I have. Attempted Solutions I have tried using the Find() and the SingleOrDefault() methods, but they just return the model I currently have. Example Code private string ArchiveChanges(T updatedEntity) { //Here is the problem! //oldEntity is the same as updatedEntity T oldEntity = DbSet.SingleOrDefault(x => x.ID == updatedEntity.ID); Dictionary<string, object> changed = new Dictionary<string, object>(); foreach (var propertyInfo in typeof(T).GetProperties()) { var property = typeof(T).GetProperty(propertyInfo.Name); //Get the old value and the new value from the models var newValue = property.GetValue(updatedEntity, null); var oldValue = property.GetValue(oldEntity, null); //Check to see if the values are equal if (!object.Equals(newValue, oldValue)) { //Values have changed ... log it changed.Add(propertyInfo.Name, newValue); } } var ser = new System.Web.Script.Serialization.JavaScriptSerializer(); return ser.Serialize(changed); } public override void Update(T entityToUpdate) { //Do something with this string json = ArchiveChanges(entityToUpdate); entityToUpdate.AuditInfo.Updated = DateTime.Now; entityToUpdate.AuditInfo.UpdatedBy = Thread.CurrentPrincipal.Identity.Name; base.Update(entityToUpdate); }

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  • PropertyInfo.GetValue() - how do you index into a generic parameter using reflection in C#?

    - by flesh
    This (shortened) code.. for (int i = 0; i < count; i++) { object obj = propertyInfo.GetValue(Tcurrent, new object[] { i }); } .. is throwing a 'TargetParameterCountException : Parameter count mismatch' exception. The underlying type of 'propertyInfo' is a Collection of some T. 'count' is the number of items in the collection. I need to iterate through the collection and perform an operation on obj. Advice appreciated.

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  • Get derived class type from a base's class static method

    - by Marco Bettiolo
    Hi, i would like to get the type of the derived class from a static method of its base class. How can this be accomplished? Thanks! class BaseClass { static void Ping () { Type t = this.GetType(); // should be DerivedClass, but it is not possible with a static method } } class DerivedClass : BaseClass {} // somewhere in the code DerivedClass.Ping();

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  • How to reduce this IF-Else ladder in c#

    - by Rohit
    This is the IF -Else ladder which I have created to focus first visible control on my form.According to the requirement any control can be hidden on the form.So i had to find first visible control and focus it. if (ddlTranscriptionMethod.Visible) { ddlTranscriptionMethod.Focus(); } else if (ddlSpeechRecognition.Visible) { ddlSpeechRecognition.Focus(); } else if (!SliderControl1.SliderDisable) { SliderControl1.Focus(); } else if (ddlESignature.Visible) { ddlESignature.Focus(); } else { if (tblDistributionMethods.Visible) { if (chkViaFax.Visible) { chkViaFax.Focus(); } else if (chkViaInterface.Visible) { chkViaInterface.Focus(); } else if (chkViaPrint.Visible) { chkViaPrint.Focus(); } else { chkViaSelfService.Focus(); } } } Is there any other way of doing this. I thought using LINQ will hog the performance as i have to tranverse the whole page collection. I am deep on page which has masterpages.Please suggest.

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  • Can I pass a non-generic type where a generic type is expected?

    - by Water Cooler v2
    I want to define a set of classes that collect and persist data. I want to call them either on-demand basis, or in a chain-of-responsibility fashion, as the caller pleases. To support the chaining, I have declared my interface like so: interface IDataManager<T, K> { T GetData(K args); void WriteData(Stream stream); void WriteData(T data, Stream stream); IDataCollectionPolicy Policy; IDataManager<T, K> NextDataManager; } But the T's and K's for each concrete types will be different. If I give it like this: IDataManager<T, K> NextDataManager; I assume that the calling code will only be able to chain types that have the same T's and K's. Is there a way I can have it chain any type of IDataManager? One thing that occurs to me is to have IDataManager inherit from a non-generic IDataManager like so: interface IDataManager { } interface IDataManager<T, K>: IDataManager { T GetData(K args); void WriteData(Stream stream); void WriteData(T data, Stream stream); IDataCollectionPolicy Policy; IDataManager NextDataManager; } Is this going to work?

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  • Why does this Razor syntax gives compilation errors?

    - by dotnetN00b
    I either get a "you need a ; here" or a "best overloaded match has invalid arguments" errors. <tbody> <tr> @for (int i = 0; i < startDay; ++i) { @:<td><span></span><span></span></td> } @for (int j = startDay; j < ((numberOfDays + startDay) - 1); ++j) { <td> <span>@startCount</span> <br /> <span> @{ var todaysEvents = Model.ToList().FindAll(d => d.CalDate.Day == j); foreach(HTMLMVCCalendar.Models.CalendarModel eventsToday in todaysEvents) { foreach(HTMLMVCCalendar.Models.EventModel eventToday in eventsToday.CalEvents) { @eventToday.DayCode.ToString // error here @:<br /> @eventToday.Subject // error here @:<br /> @eventToday.EventDesc //error here } @:<br /> } } </span> </td> if ((j + 1) % 7 == 0) { @:</tr><tr> } @++startCount; } </tr> </tbody>

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  • C++ Generic List Assignment

    - by S73417H
    I've clearly been stuck in Java land for too long... Is it possible to do the C++ equivalent of the following Java code: // Method List<Bar> getBars() { return new LinkedList<Bar>(); } // Assignment statement. List<Foo> stuff = getBars(); Where Foo is a sub-class of Bar. So in C++.... std::list<Bar> & getBars() { std::list<Bar> bars; return bars; } std::list<Foo> stuff = getBars(); Hope that makes sense....

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  • Modern way to validate POST-data in MVC 2

    - by zerkms
    There are a lot of articles devoted to working with data in MVC, and nothing about MVC 2. So my question is: what is the proper way to handle POST-query and validate it. Assume we have 2 actions. Both of them operates over the same entity, but each action has it's own separated set of object properties that should be bound in automatic manner. For example: Action "A" should bind only "Name" property of object, taken from POST-request Action "B" should bind only "Date" property of object, taken from POST-request As far as I understand - we cannot use Bind attribute in this case. So - what are the best practices in MVC2 to handle POST-data and probably validate it.

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  • Using AJAX to return SelectList selected value

    - by Adventure
    At risk of asking the obvious... I need to use AJax.ActionLink to send the current value of a SelectList back to my controller. How do I do that? Below is part of my current View. I need to replace "15" with the current value of the SelectList. <% If Model.ShoppingListNames IsNot Nothing Then%> <%: Html.DropDownList("ShoppingListNames", Model.ShoppingListNames)%> <%: Ajax.ActionLink("Add to List", "AdjustMaterials", "Docs", New With {.userDocId = 15, .prodId = Model.ID, .quantity = 1}, New AjaxOptions With {.OnSuccess = "handleUpdate"})%> <% End If%>

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  • Custom librairies with Razor with the release version of MVC 3

    - by Maxim
    So I'm developing an in-house library for MVC 3 and I want to add it to my project. I added it to my web.config. I added the assembly and added it to the pages - namespaces section and... no. Doesn't work. I tried recompiling, etc... but Razor doesn't like it at all. It's not an intellisense problem... the site can't run if I use my defined namespace. The only way that I made it work was by using the following statements: @using Sample.Helpers I don't want to use it in the pages. I want to be able to deploy it to many projects and adding it to the web.config is definitely the way to go. Anyone ran into this problem?

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  • Do I always need to rebuild the project containing references to sub project's dll, if sub projects

    - by Puneet Dudeja
    I have a solution containing 4 class library projects and one "web site" project. The web site project contains references to the 3 class library projects, whenever I make changes in any of the class library projects, the only option I see is to rebuild the web site which takes a lot of time. Is there any option that I can only update the dll references and the changes are reflected in the web site project ?

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  • How to use unlinked result of linq?

    - by user46503
    Hello, for example I'm trying to get the data from database like: using (ExplorerDataContext context = new ExplorerDataContext()) { ObjectQuery<Store> stores = context.Store; ObjectQuery<ProductPrice> productPrice = context.ProductPrice; ObjectQuery<Product> products = context.Product; res = from store in stores join pp in productPrice on store equals pp.Store join prod in products on pp.Product equals prod select store; } After this code I cannot transfer the result to some another method because the context doesn't exist more. How could I get the unlinked result independent on the context? Thanks

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