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  • How cast in c#/.net 3.5 works? for types with '?'

    - by Inez
    This is my code which works public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : (decimal?) null; } and this one doesn't work public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : null; } giving the compilator error: Error 1 Type of conditional expression cannot be determined because there is no implicit conversion between 'decimal' and '' I wonder why? any ideas?

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  • How does cast in C#/.NET 3.5 work for types with '?'

    - by Inez
    This is my code which works public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : (decimal?) null; } and this one doesn't work public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : null; } giving the compiler error: Error 1 Type of conditional expression cannot be determined because there is no implicit conversion between 'decimal' and '<null>' I wonder why? any ideas?

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  • Nonstatic conversion functions; Casting different types, e.g. DirectX vector to OpenGL vector

    - by Markus
    I am currently working on a game "engine" that needs to move values between a 3D engine, a physics engine and a scripting language. Since I need to apply vectors from the physics engine to 3D objects very often and want to be able to control both the 3D, as well as the physics objects through the scripting system, I need a mechanism to convert a vector of one type (e.g. vector3d<float>) to a vector of the other type (e.g. btVector3). Unfortunately I can make no assumptions on how the classes/structs are laid out, so a simple reinterpret_cast probably won't do. So the question is: Is there some sort of 'static'/non-member casting method to achieve basically this: vector3d<float> operator vector3d<float>(btVector3 vector) { // convert and return } btVector3 operator btVector3(vector3d<float> vector) { // convert and return } Right now this won't compile since casting operators need to be member methods. (error C2801: 'operator foo' must be a non-static member)

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  • How do you override operator == when using interfaces instead of actual types?

    - by RickL
    I have some code like this: How should I implement the operator == so that it will be called when the variables are of interface IMyClass? public class MyClass : IMyClass { public static bool operator ==(MyClass a, MyClass b) { if (ReferenceEquals(a, b)) return true; if ((Object)a == null || (Object)b == null) return false; return false; } public static bool operator !=(MyClass a, MyClass b) { return !(a == b); } } class Program { static void Main(string[] args) { IMyClass m1 = new MyClass(); IMyClass m2 = new MyClass(); MyClass m3 = new MyClass(); MyClass m4 = new MyClass(); Console.WriteLine(m1 == m2); // does not go into custom == function. why not? Console.WriteLine(m3 == m4); // DOES go into custom == function } }

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  • How can I use EF in windows forms to insert new data ?

    - by Al0NE
    Hi Maybe it's simple question, but it's my first time with EF + win app so ... I'm building win app with EF by adding edmx as data source then drag and drop the tables to get navigator and binding source .. when I press the add button in the navigator it allows me to enter new data but when I save the context I get NULL data for all fields except the auto increment field ( the ID field ).... What should I do to save many entries ...? DO I have to loop over all the entities in the binding source and add them to the context ?? Thanx in advance Update: I forgot to say that when i use data grid view it adds the items correctly but with "Details" it didn't ..

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  • Double data entry system using Infopath 2007 how to compare 2 infopath documents for differences ?

    - by bugBurger
    How to compare 2 infopath documents craeted using double data entry system for differences ? We have a small project contains few infopath forms. Client is using double data entry system to reduce the errors. We are maintaining entry number in infopath form to seperate each entry. Note: I know we can compare xml data files of 2 documents. (xml data file has field names like field1,field2 and so on..while on form that field1 represent some meaninngful text) But the question is we want to compare it Visually side by side. Any difference should highlight the field.

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  • How can I build a voting system to support multiple types of objects to vote on?

    - by Kyle Hayes
    I'm really looking for something very similar to the way SO is setup where a few different kinds of things can be voted on (questions AND answers). What kind of DB schema, generally, could I use to support voting on many different kinds of objects? Would I have a single Vote table that would have references to other objects in the database? Or do I have to have or should have a separate vote table for each of the objects I would like to vote on.

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  • When encrypting data that is not an even multiple of the block size do I have to send a complete las

    - by WilliamKF
    If I am using a block cipher such as AES which has a block size of 128 bits, what do I do if my data is not an even multiple of 128 bits? I am working with packets of data and do not want to change the size of my packet when encrypting it, yet my data is not an even multiple of 128? Does the AES block cipher allow handling of a final block that is short without changing the size of my message once encrypted?

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  • How to have an excel addin read rows from a worksheet until no more data?

    - by user169867
    I've started writing a Com addin for Excel 2003 using C#. I'm looking for a code example showing how to read in cell data from the active worksheet. I've seen that you can write code like this: Excel.Range firstCell = ws.get_Range("A1", Type.Missing); Excel.Range lastCell = ws.get_Range("A10", Type.Missing); Excel.Range worksheetCells = ws.get_Range(firstCell, lastCell); to grab a range of cells. What I could use help with is how to read the cell data when you don't know how many rows of data there are. I may be able to determine the starting row that the data will be begin at, but there will be an unkown number of rows of data to read. Could someone provide me w/ an example of how to read rows from the worksheet until you come across a row of empty cells? Also does anyone know how to grab the range of cells the user has selected? Any help would be greatly appreciated. This seems like a powerful dev tool, but I'm having trouble finding detailed documentation to help me learn it :)

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  • Django Problem - trying to access data entered into a form and feed it through a different page

    - by John Hoke
    OK, so let me give you an overview first. I have this site and in it there is a form section. When you access that section you can view or start a new project. Each project has 3-5 different forms. My problem is that I don't want viewers to have to go through all 3-5 pages to see the relevant information they need. Instead I want to give each project a main page where all the essential data entered into the forms is shown as non-editable data. I hope this makes sense. So I need to find a way to access all that data from the different forms for each project and to feed that data into the new page I'll be calling "Main". Each project will have a separate main page for itself. I'm pretty much clueless as to how I should do this, so any help at all would be appreciated. Thanks

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  • How can I improve my select query for storing large versioned data sets?

    - by Jason Francis
    At work, we build large multi-page web applications, consisting mostly of radio and check boxes. The primary purpose of each application is to gather data, but as users return to a page they have previously visited, we report back to them their previous responses. Worst-case scenario, we might have up to 900 distinct variables and around 1.5 million users. For several reasons, it makes sense to use an insert-only approach to storing the data (as opposed to update-in-place) so that we can capture historical data about repeated interactions with variables. The net result is that we might have several responses per user per variable. Our table to collect the responses looks something like this: CREATE TABLE [dbo].[results]( [id] [bigint] IDENTITY(1,1) NOT NULL, [userid] [int] NULL, [variable] [varchar](8) NULL, [value] [tinyint] NULL, [submitted] [smalldatetime] NULL) Where id serves as the primary key. Virtually every request results in a series of insert statements (one per variable submitted), and then we run a select to produce previous responses for the next page (something like this): SELECT t.id, t.variable, t.value FROM results t WITH (NOLOCK) WHERE t.userid = '2111846' AND (t.variable='internat' OR t.variable='veteran' OR t.variable='athlete') AND t.id IN (SELECT MAX(id) AS id FROM results WITH (NOLOCK) WHERE userid = '2111846' AND (t.variable='internat' OR t.variable='veteran' OR t.variable='athlete') GROUP BY variable) Which, in this case, would return the most recent responses for the variables "internat", "veteran", and "athlete" for user 2111846. We have followed the advice of the database tuning tools in indexing the tables, and against our data, this is the best-performing version of the select query that we have been able to come up with. Even so, there seems to be significant performance degradation as the table approaches 1 million records (and we might have about 150x that). We have a fairly-elegant solution in place for sharding the data across multiple tables which has been working quite well, but I am open for any advice about how I might construct a better version of the select query. We use this structure frequently for storing lots of independent data points, and we like the benefits it provides. So the question is, how can I improve the performance of the select query? I assume the nested select statement is a bad idea, but I have yet to find an alternative that performs as well. Thanks in advance. NB: Since we emphasize creating over reading in this case, and since we never update in place, there doesn't seem to be any penalty (and some advantage) for using the NOLOCK directive in this case.

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  • Open generic interface types of open implementation don't equal interface type?

    - by George Mauer
    Here's a test that should, in my opinion be passing but is not. [TestMethod] public void can_get_open_generic_interface_off_of_implementor() { typeof(OpenGenericWithOpenService<>).GetInterfaces().First() .ShouldEqual(typeof(IGenericService<>)); } public interface IGenericService<T> { } public class OpenGenericWithOpenService<T> : IGenericService<T> { } Why does this not pass? Given Type t = typeof(OpenGenericWithOpenService<>) how do I get typeof(IGenericService<)? I'm generally curious, but if you're wondering what I'm doing, I'm writing a Structuremap convention that forwards all interfaces implemented by a class to the implementation (as a singleton).

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  • How could I use AJAX to create a Json data source .txt file?

    - by Adam
    I'm creating a form that collects standard information about customers. When the user hits save, I would like to create a .txt file that would be used to later retrieve all of the data collected from customers. I'm using DataTables which is a jQuery plugin to display the data. The .txt file would be formatted to be saved as such: { "aaData": [ ["client 1 name","address","city","state","zip"], ["client 2 name","address","city","state","zip"], ["client 3 name","address","city","state","zip"], ... ["client x name","address","city","state","zip"] ] } Where "aaData": is used by DataTables. This is going to part of an iPhone app, so the data source has to be very small and not reliant on a constant connection to a server, so, essentially, a client-side data source. The .txt file has to also be updated when edited and saved, and then replaced every time it is downloaded.

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  • Implicit constructor available for all types derived from Base excepted the current type?

    - by Vincent
    The following code sum up my problem : template<class Parameter> class Base {}; template<class Parameter1, class Parameter2, class Parameter> class Derived1 : public Base<Parameter> { }; template<class Parameter1, class Parameter2, class Parameter> class Derived2 : public Base<Parameter> { public : // Copy constructor Derived2(const Derived2& x); // An EXPLICIT constructor that does a special conversion for a Derived2 // with other template parameters template<class OtherParameter1, class OtherParameter2, class OtherParameter> explicit Derived2( const Derived2<OtherParameter1, OtherParameter2, OtherParameter>& x ); // Now the problem : I want an IMPLICIT constructor that will work for every // type derived from Base EXCEPT // Derived2<OtherParameter1, OtherParameter2, OtherParameter> template<class Type, class = typename std::enable_if</* SOMETHING */>::type> Derived2(const Type& x); }; How to restrict an implicit constructor to all classes derived from the parent class excepted the current class whatever its template parameters, considering that I already have an explicit constructor as in the example code ? EDIT : For the implicit constructor from Base, I can obviously write : template<class OtherParameter> Derived2(const Base<OtherParameter>& x); But in that case, do I have the guaranty that the compiler will not use this constructor as an implicit constructor for Derived2<OtherParameter1, OtherParameter2, OtherParameter> ? EDIT2: Here I have a test : (LWS here : http://liveworkspace.org/code/cd423fb44fb4c97bc3b843732d837abc) #include <iostream> template<typename Type> class Base {}; template<typename Type> class Other : public Base<Type> {}; template<typename Type> class Derived : public Base<Type> { public: Derived() {std::cout<<"empty"<<std::endl;} Derived(const Derived<Type>& x) {std::cout<<"copy"<<std::endl;} template<typename OtherType> explicit Derived(const Derived<OtherType>& x) {std::cout<<"explicit"<<std::endl;} template<typename OtherType> Derived(const Base<OtherType>& x) {std::cout<<"implicit"<<std::endl;} }; int main() { Other<int> other0; Other<double> other1; std::cout<<"1 = "; Derived<int> dint1; // <- empty std::cout<<"2 = "; Derived<int> dint2; // <- empty std::cout<<"3 = "; Derived<double> ddouble; // <- empty std::cout<<"4 = "; Derived<double> ddouble1(ddouble); // <- copy std::cout<<"5 = "; Derived<double> ddouble2(dint1); // <- explicit std::cout<<"6 = "; ddouble = other0; // <- implicit std::cout<<"7 = "; ddouble = other1; // <- implicit std::cout<<"8 = "; ddouble = ddouble2; // <- nothing (normal : default assignment) std::cout<<"\n9 = "; ddouble = Derived<double>(dint1); // <- explicit std::cout<<"10 = "; ddouble = dint2; // <- implicit : WHY ?!?! return 0; } The last line worry me. Is it ok with the C++ standard ? Is it a bug of g++ ?

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  • How to filter using a dropdown in Knockout

    - by user517406
    I have just started using Knockout and I want to filter my data that I am displaying in my UI by selecting an item from a dropdown. I have got so far, but I cannot get the selected value from my dropdown yet, and then after that I need to actually filter the data displayed based upon that value. Here is my code so far : @model Models.Fixture @{ ViewBag.Title = "Fixtures"; Layout = "~/Areas/Development/Views/Shared/_Layout.cshtml"; } @Scripts.Render("~/bundles/jqueryval") <script type="text/javascript" src="@Url.Content("~/Scripts/knockout-2.1.0.js")"></script> <script type="text/javascript"> function FixturesViewModel() { var self = this; var baseUri = '@ViewBag.ApiUrl'; self.fixtures = ko.observableArray(); self.teams = ko.observableArray(); self.update = function (fixture) { $.ajax({ type: "PUT", url: baseUri + '/' + fixture.Id, data: fixture }); }; self.sortByAwayTeamScore = function () { this.fixtures.sort(function(a, b) { return a.AwayTeamScore < b.AwayTeamScore ? -1 : 1; }); }; self.select = function (team) { }; $.getJSON("/api/fixture", self.fixtures); $.getJSON("/api/team", self.teams); } $(document).ready(function () { ko.applyBindings(new FixturesViewModel()); }); </script> <div class="content"> <div> <table><tr><td><select data-bind="options: teams, optionsText: 'TeamName', optionsCaption: 'Select...', optionsValue: 'TeamId', click: $root.select"> </select></td></tr></table> <table class="details ui-widget-content"> <thead> <tr><td>FixtureId</td><td>Season</td><td>Week</td><td>AwayTeam</td><td><a id="header" data-bind='click: sortByAwayTeamScore'>AwayTeamScore</a></td><td>HomeTeam</td><td>HomeTeamScore</td></tr> </thead> <tbody data-bind="foreach: fixtures"> <tr> <td><span data-bind="text: $data.Id"></span></td> <td><span data-bind="text: $data.Season"></span></td> <td><span data-bind="text: $data.Week"></span></td> <td><span data-bind="text: $data.AwayTeamName"></span></td> <td><input type="text" data-bind="value: $data.AwayTeamScore"/></td> <td><span data-bind="text: $data.HomeTeamName"></span></td> <td><input type="text" data-bind="value: $data.HomeTeamScore"/></td> <td><input type="button" value="Update" data-bind="click: $root.update"/></td> </tr> </tbody> </table> </div> </div> Can anybody please advise on this?

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  • Sql Server Compact Edition 3.5: Does the data persist in the database file?

    - by jerbersoft
    Hi guys, I have this question in which I have a SQL Server Compact Edition database for a desktop application. I am completely new to Sql Server Compact Edition. The question is, does the data inserted in the database persist even if the application is shut down or restarted? Coz I cant seem to find my data when using Sql Server Management Studio to manage the database. Am I missing anything/something? EDIT: Is SQL Server Compact Edition used for caching local data only? We cant use it like what we normally do on Sql Server Express for example managing data using Sql Server Management Studio?

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  • MIN array function non zeros only

    - by user1717622
    I have been trying to get this array function to output (non-zero) minimum values in the 'FINAL DATA' AE column. Can you see a structural error in this formula? =IF($C$4="All EMEA", MIN(IF('FINAL DATA'!$2:$AE$250000<>0, ('FINAL DATA'!$J$2:$J$250000=$C$4)*('FINAL DATA'!$E$2:$E$250000=$E$4)*( 'FINAL DATA'!$AE$2:$AE$250000))), MIN(IF('FINAL DATA'!$AE$2:$AE$250000<>0, ('FINAL DATA'!$K$2:$K$250000=$C$4)*('FINAL DATA'!$E$2:$E$250000=$E$4)*( 'FINAL DATA'!$AE$2:$AE$250000))) )

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