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• Get controls ClientID/UniqueID between DetailsView and UpdatePanel

  - by robertpnl

  Hi guys, I like to know how to get the ClientID/UniqueID of a control inside a Detailsview controls EditItemTemplate element and when DetailsViews changing to Edit mode and DetailsView is inside a AJAX UpdatePanel. Without UpdatePanel, during PostBack I can get the ClientID's control, but now with an UpdatePanel. <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional"> <ContentTemplate> <asp:DetailsView ID="DetailsView1" runat="server" DataSourceID="SqlDataSource1" AllowPaging="true" AutoGenerateEditButton="true"> <Fields> <asp:TemplateField> <EditItemTemplate> <asp:CheckBox runat="server" ID="chkboxTest" Text="CHECKBOX" /> </EditItemTemplate> </asp:TemplateField> </Fields> </asp:DetailsView> </ContentTemplate> </asp:UpdatePanel> As you see, the EditItemTemplate contains a Checkbox control. So i'm trying to get the ClientID of this checkbox when Detailsview is changing to the Edit mode. I need this value for handling Javascript. Catching the events ChangingMode/ChangedMode doesn't work; chkbox is null: void DetailsView1_ModeChanged(object sender, EventArgs e) { if (DetailsView1.CurrentMode == DetailsViewMode.Edit) var chkbox = DetailsView1.Rows[0].FindControl("chkxboxTest"); // <== is null } Maybe i'm using the wrong event? Someone can give me a tip about this? Thanks.

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• IEnumerable.Cast not calling cast overload

  - by Martin Neal

  I'm not understanding something about the way .Cast works. I have an explicit (though implicit also fails) cast defined which seems to work when I use it "regularly", but not when I try to use .Cast. Why? Here is some compilable code that demonstrates my problem. public class Class1 { public string prop1 { get; set; } public int prop2 { get; set; } public static explicit operator Class2(Class1 c1) { return new Class2() { prop1 = c1.prop1, prop2 = c1.prop2 }; } } public class Class2 { public string prop1 { get; set; } public int prop2 { get; set; } } void Main() { Class1[] c1 = new Class1[] { new Class1() {prop1 = "asdf",prop2 = 1}}; //works Class2 c2 = (Class2)c1[0]; //doesn't work: Compiles, but throws at run-time //InvalidCastException: Unable to cast object of type 'Class1' to type 'Class2'. Class2 c3 = c1.Cast<Class2>().First(); }

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• How does static code run with multiple threads?

  - by Krisc

  I was reading http://stackoverflow.com/questions/1511798/threading-from-within-a-class-with-static-and-non-static-methods and I am in a similar situation. I have a static method that pulls data from a resource and creates some runtime objects based on the data. static class Worker{ public static MyObject DoWork(string filename){ MyObject mo = new MyObject(); // ... does some work return mo; } } The method takes awhile (in this case it is reading 5-10mb files) and returns an object. I want to take this method and use it in a multiple thread situation so I can read multiple files at once. Design issues / guidelines aside, how would multiple threads access this code? Let's say I have something like this... class ThreadedWorker { public void Run() { Thread t = new Thread(OnRun); t.Start(); } void OnRun() { MyObject mo = Worker.DoWork("somefilename"); mo.WriteToConsole(); } } Does the static method run for each thread, allowing for parallel execution?

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• Any merit to a lazy-ish juxt function?

  - by NielsK

  In answering a question about a function that maps over multiple functions with the same arguments (A: juxt), I came up with a function that basically took the same form as juxt, but used map: (defn could-be-lazy-juxt [& funs] (fn [& args] (map #(apply %1 %2) funs (repeat args)))) => ((juxt inc dec str) 1) [2 0 "1"] => ((could-be-lazy-juxt inc dec str) 1) (2 0 "1") => ((juxt * / -) 6 2) [12 3 4] => ((could-be-lazy-juxt * / -) 6 2) (12 3 4) As posted in the original question, I have little clue about the laziness or performance of it, but timing in the REPL does suggest something lazy-ish is going on. => (time (apply (juxt + -) (range 1 100))) "Elapsed time: 0.097198 msecs" [4950 -4948] => (time (apply (could-be-lazy-juxt + -) (range 1 100))) "Elapsed time: 0.074558 msecs" (4950 -4948) => (time (apply (juxt + -) (range 10000000))) "Elapsed time: 1019.317913 msecs" [49999995000000 -49999995000000] => (time (apply (could-be-lazy-juxt + -) (range 10000000))) "Elapsed time: 0.070332 msecs" (49999995000000 -49999995000000) I'm sure this function is not really that quick (the print of the outcome 'feels' about as long in both). Doing a 'take x' on the function only limits the amount of functions evaluated, which probably is limited in it's applicability, and limiting the other parameters by 'take' should be just as lazy in normal juxt. Is this juxt really lazy ? Would a lazy juxt bring anything useful to the table, for instance as a compositing step between other lazy functions ? What are the performance (mem / cpu / object count / compilation) implications ? Is that why the Clojure juxt implementation is done with a reduce and returns a vector ? Edit: Somehow things can always be done simpler in Clojure. (defn could-be-lazy-juxt [& funs] (fn [& args] (map #(apply % args) funs)))

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• Incorrect syntax inserting data into table

  - by SelectDistinct

  I am having some trouble with my update() method. The idea is that the user Provides a recipe name, ingredients, instructions and then selects an image using Filestream. Once the user clicks 'Add Recipe' this will call the update method, however as things stand I am getting an error which is mentioning the contents of the text box: Here is the update() method code: private void updatedata() { // filesteam object to read the image // full length of image to a byte array try { // try to see if the image has a valid path if (imagename != "") { FileStream fs; fs = new FileStream(@imagename, FileMode.Open, FileAccess.Read); // a byte array to read the image byte[] picbyte = new byte[fs.Length]; fs.Read(picbyte, 0, System.Convert.ToInt32(fs.Length)); fs.Close(); //open the database using odp.net and insert the lines string connstr = @"Server=mypcname\SQLEXPRESS;Database=RecipeOrganiser;Trusted_Connection=True"; SqlConnection conn = new SqlConnection(connstr); conn.Open(); string query; query = "insert into Recipes(RecipeName,RecipeImage,RecipeIngredients,RecipeInstructions) values (" + textBox1.Text + "," + " @pic" + "," + textBox2.Text + "," + textBox3.Text + ")"; SqlParameter picparameter = new SqlParameter(); picparameter.SqlDbType = SqlDbType.Image; picparameter.ParameterName = "pic"; picparameter.Value = picbyte; SqlCommand cmd = new SqlCommand(query, conn); cmd.Parameters.Add(picparameter); cmd.ExecuteNonQuery(); MessageBox.Show("Image successfully saved"); cmd.Dispose(); conn.Close(); conn.Dispose(); Connection(); } } catch (Exception ex) { MessageBox.Show(ex.Message); } } Can anyone see where I have gone wrong with the insert into Recipes query or suggest an alternative approach to this part of the code?

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• Issue while saving image using savefiledialog

  - by user1097772

  I'm using savefiledialog to save an image. Canvas is picturebox and the loaded image is bitmap. When I try to save it the file is created but somehow corrupted. Cause when I try againt load the image or show in different viewer it doesn't work - I mean the saved file is corrupted. There is an method for saving image. private void saveFileDialog1_FileOk(object sender, CancelEventArgs e) { System.IO.FileStream fs = (System.IO.FileStream)saveFileDialog1.OpenFile(); try { switch (saveFileDialog1.FilterIndex) { case 1: canvas.Image.Save(saveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Bmp); break; case 2: canvas.Image.Save(saveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Jpeg); break; case 3: canvas.Image.Save(saveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Png); break; case 4: canvas.Image.Save(saveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Tiff); break; } } catch (Exception ex) { System.Console.WriteLine("Exception " + ex); } I should also mention the property Filter. saveFileDialog1.Filter has value: bmp (*.bmp)|*.bmp|jpeg (*.jpeg)|*.jpeg|png (*.png)|*.png|tiff (*.tiff)|*.tiff

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• Question about decorator pattern and the abstract decorator class?

  - by es11

  This question was asked already here, but rather than answering the specific question, descriptions of how the decorator pattern works were given instead. I'd like to ask it again because the answer is not immediately evident to me just by reading how the decorator pattern works (I've read the wikipedia article and the section in the book Head First Design Patterns). Basically, I want to know why an abstract decorator class must be created which implements (or extends) some interface (or abstract class). Why can't all the new "decorated classes" simply implement (or extend) the base abstract object themselves (instead of extending the abstract decorator class)? To make this more concrete I'll use the example from the design patterns book dealing with coffee beverages: There is an abstract component class called Beverage Simple beverage types such as HouseBlend simply extend Beverage To decorate beverage, an abstract CondimentDecorator class is created which extends Beverage and has an instance of Beverage Say we want to add a "milk" condiment, a class Milk is created which extends CondimentDecorator I'd like to understand why we needed the CondimentDecorator class and why the class Milk couldn't have simply extended the Beverage class itself and been passed an instance of Beverage in its constructor. Hopefully this is clear...if not I'd simply like to know why is the abstract decorator class necessary for this pattern? Thanks. Edit: I tried to implement this, omitting the abstract decorator class, and it seems to still work. Is this abstract class present in all descriptions of this pattern simply because it provides a standard interface for all of the new decorated classes?

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• Designing DAOs around a JSON API for iPhone Development

  - by Bob Spryn

  So I've been trying to design a clean way of grabbing data for my models in iPhone land. All the data for my application is coming from JSON API's. So right now when a VC needs some models, it does the JSON call itself (asynch) and when it receives the data, it builds the models. It works, but I'm trying to think of a cleaner method whereby the DAO's retrieve the information for me and return the models, all in an async manner. My initial thought is build a protocol for my DAOs, such that the VC would instantiate a DAO and make itself the delegate. When you requested data [DAOinstance getAllUsers] the DAO would do all the network request stuff, and then when it had the data, it would call a method on its delegate (the VC) to pass the data. So I think that's a cool solution, but realized that if I needed to use the same DAO for different purposes in the same VC, my delegate method would have to branch logic depending on which DAO instance initiated the request. So my second thought was to be able to pass 'handler' selectors to the DAO object a la typical javascript patterns. So instead of an official protocol, I would say something like [DAOinstance getAllUsersWithSelector:"TheHandlerFunctionOnMyVC:"] Then when the DAO completed its network activities, it would call the passed selector on the VC, and pass the data back. So am I headed in the wrong direction entirely here? Seems like maybe an ok way to go. Any pointers or articles on designing this kind of data layer would be sweet. Thanks! Bob

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• Remove Empty Attributes from XML

  - by er4z0r

  Hi, I have a buggy xml that contains empty attributes and I have a parser that coughs on empty attributes. I have no control over the generation of the xml nor over the parser that coughs on empty attrs. So what I want to do is a pre-processing step that simply removes all empty attributes. I have managed to find the empty attribus, but now I don't know how to remove them: XPathFactory xpf = XPathFactory.newInstance(); XPath xpath = xpf.newXPath(); XPathExpression expr = xpath.compile("//@*"); Object result = expr.evaluate(d, XPathConstants.NODESET); if (result != null) { NodeList nodes = (NodeList) result; for(int node=0;node<nodes.getLength();node++) { Node n = nodes.item(node); if(isEmpty(n.getTextContent())) { this.log.warn("Found empty attribute declaration "+n.toString()); NamedNodeMap parentAttrs = n.getParentNode().getAttributes(); parentAttrs.removeNamedItem(n.getNodeName()); } } } This code gives me a NPE when accessing n.getParentNode().getAttributes(). But how can I remove the empty attribute from an element, when I cannot access the element?

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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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• How to implement a download for dynamic files in asp.net with masterpages

  - by Tim

  Hello, the title says it all. I have seen some similar questions on SO like this or this, but either i have overlooked something or my requirement is different, neither works. My situation is following: i have a Masterpage one of its contentpage is called MasterData.aspx MasterData has an asp.net ajax tabcontainer control with one usercontrol in every tabpanel these usercontrols(f.e. MD_Customer.ascx)hold the main content(like a normal page) they all have GridViews in it and i want to provide an Excel-Export-Button What i've tried is is to use an iframe like here. But the function that adds the iframe to the document gets never called and therefore i never see the save-as-dialog. Maybe this is caused by using a MasterPage. Does somebody has an idea on how to provide a button in an UpdatePanel that causes an async postback, so that i can generate a CSV dynamically in codebehind and write it to the response? Thank you in advance. aspx-markup: <asp:UpdatePanel ID="UpdGridInfo" runat="server" > <ContentTemplate> <asp:Label ID="LblInfo" Font-Underline="false" runat="server" CssClass="content" ></asp:Label>&nbsp;&nbsp; <asp:ImageButton ToolTip="export to Excel" style="vertical-align:bottom" ID="BtnExcelExport" ImageUrl="~/images/excel2007logo.png" runat="server" /> </ContentTemplate> </asp:UpdatePanel> and the BtnExportExcel codebehind handler(of course it cannot work to write the csv to the response of this page): Private Sub BtnExcelExport_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles BtnExcelExport.Click Dim csv As String = tableToCsv(DirectCast(Me.GridSource, DataTable)) Response.AddHeader("Content-disposition", "attachment; filename=RuleConfigurationFile.csv") Response.ContentType = "application/octet-stream" Response.Write(csv) Response.End() End Sub

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• ASP.NET ListView, custom DataSources, and editing items

  - by Andrew Shepherd

  The MSDN walkthroughs provide a number of examples where you can drag a DataSource from the toolbox, run through some simple configuration steps, then drag a ListView onto the screen, point it at the DataSource, and hey - you've got full table editing. Now I'm trying to write my own DataSource class (a class that implements System.Web.UI.IDataSource) and my own DataSourceView class. I now assign an instance of this custom DataSource class to the ListView.DataSource propery. The display of all the items is working well. However, updating, inserting and deleting just is not working. I'm overriding every function I can in my DataSourceView class, and they just aren't being called. This is such a huge topic, I'll focus this question on one simple example: When you press the "Edit" button (the button inside the ItemTemplate with a CommandName of "Edit", you expect the ItemTemplate to be replaced by an EditItemTemplate. This did not happen. The only way I could get it to happen was to handle the onitemediting event. protected void _listViewPublicHolidays_ItemEditing(object sender, ListViewEditEventArgs e) { _listViewPublicHolidays.EditIndex = e.NewEditIndex; _listViewPublicHolidays.DataBind(); } This is hardly a problem, but how come I had to do it at all? In the MSDN walkthroughs where I attach a ListView to a LinqDataSource, this code doesn't have to be written. Can someone who's been here before hazard a guess as to what would be different or missing in my custom datasource?

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• DataReader already open when using LINQ

  - by Jamie Dixon

  I've got a static class containing a static field which makes reference to a wrapper object of a DataContext. The DataContext is basically generated by Visual Studio when we created a dbml file & contains methods for each of the stored procedures we have in the DB. Our class basically has a bunch of static methods that fire off each of these stored proc methods & then returns an array based on a LINQ query. Example: public static TwoFieldBarData[] GetAgesReportData(string pct) { return DataContext .BreakdownOfUsersByAge(Constants.USER_MEDICAL_PROFILE_KEY, pct) .Select(x => new TwoFieldBarData(x.DisplayName, x.LeftValue, x.RightValue, x.TotalCount)) .ToArray(); } Every now and then, we get the following error: There is already an open DataReader associated with this Command which must be closed firs This is happening intermittently and I'm curious as to what is going on. My guess is that when there's some lag between one method executing and the next one firing, it's locking up the DataContext and throwing the error. Could this be a case for wrapping each of the DataContext LINQ calls in a lock(){} to obtain exclusivity to that type and ensure other requests are queued?

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• A bit confused about OOP and PHP.

  - by Pirkka

  Hello I have programmed with procedural style a lot before and in these few months I have decided to go OOP. Im a bit confused about OOP and PHP. Lets say I have Categories table and Pages table in my database. I would like to do a page-class and a category-class. Lets say I would have a page that showed information about the category and there would be a list of pages that belong to the category. How would I implement that in OOP way? I have thought that the category class would have a property (array) that would contain all the pages that it has. Well then comes the part that I`m confused about. Should I have a method that would get all the pages with correct categoryID from the database and should I instantiate all the rows as an Page-object? Or should I have a setPages-method in the Category-class and getAllPages-method in the Pages-class and with that method I would set all the pages to the Category-class. Huh Im lost. :D

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• c++ queue template

  - by Dalton Conley

  ALright, pardon my messy code please. Below is my queue class. #include <iostream> using namespace std; #ifndef QUEUE #define QUEUE /*---------------------------------------------------------------------------- Student Class # Methods # Student() // default constructor Student(string, int) // constructor display() // out puts a student # Data Members # Name // string name Id // int id ----------------------------------------------------------------------------*/ class Student { public: Student() { } Student(string iname, int iid) { name = iname; id = iid; } void display(ostream &out) const { out << "Student Name: " << name << "\tStudent Id: " << id << "\tAddress: " << this << endl; } private: string name; int id; }; // define a typedef of a pointer to a student. typedef Student * StudentPointer; template <typename T> class Queue { public: /*------------------------------------------------------------------------ Queue Default Constructor Preconditions: none Postconditions: assigns default values for front and back to 0 description: constructs a default empty Queue. ------------------------------------------------------------------------*/ Queue() : myFront(0), myBack(0) {} /*------------------------------------------------------------------------ Copy Constructor Preconditions: requres a reference to a value for which you are copying Postconditions: assigns a copy to the parent Queue. description: Copys a queue and assigns it to the parent Queue. ------------------------------------------------------------------------*/ Queue(const T & q) { myFront = myBack = 0; if(!q.empty()) { // copy the first node myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } /*------------------------------------------------------------------------ Destructor Preconditions: none Postconditions: deallocates the dynamic memory for the Queue description: deletes the memory stored for a Queue. ------------------------------------------------------------------------*/ ~Queue() { NodePointer prev = myFront, ptr; while(prev != NULL) { ptr = prev->next; delete prev; prev = ptr; } } /*------------------------------------------------------------------------ Empty() Preconditions: none Postconditions: returns a boolean value. description: returns true/false based on if the queue is empty or full. ------------------------------------------------------------------------*/ bool empty() const { return (myFront == NULL); } /*------------------------------------------------------------------------ Enqueue Preconditions: requires a constant reference Postconditions: allocates memory and appends a value at the end of a queue description: ------------------------------------------------------------------------*/ void enqueue(const T & value) { NodePointer newNodePtr = new Node(value); if(empty()) { myFront = myBack = newNodePtr; newNodePtr->next = NULL; } else { myBack->next = newNodePtr; myBack = newNodePtr; newNodePtr->next = NULL; } } /*------------------------------------------------------------------------ Display Preconditions: requires a reference of type ostream Postconditions: returns the ostream value (for chaining) description: outputs the contents of a queue. ------------------------------------------------------------------------*/ void display(ostream & out) const { NodePointer ptr; ptr = myFront; while(ptr != NULL) { out << ptr->data << " "; ptr = ptr->next; } out << endl; } /*------------------------------------------------------------------------ Front Preconditions: none Postconditions: returns a value of type T description: returns the first value in the parent Queue. ------------------------------------------------------------------------*/ T front() const { if ( !empty() ) return (myFront->data); else { cerr << "*** Queue is empty -- returning garbage value ***\n"; T * temp = new(T); T garbage = * temp; delete temp; return garbage; } } /*------------------------------------------------------------------------ Dequeue Preconditions: none Postconditions: removes the first value in a queue ------------------------------------------------------------------------*/ void dequeue() { if ( !empty() ) { NodePointer ptr = myFront; myFront = myFront->next; delete ptr; if(myFront == NULL) myBack = NULL; } else { cerr << "*** Queue is empty -- " "can't remove a value ***\n"; exit(1); } } /*------------------------------------------------------------------------ pverloaded = operator Preconditions: requires a constant reference Postconditions: returns a const type T description: this allows assigning of queues to queues ------------------------------------------------------------------------*/ Queue<T> & operator=(const T &q) { // make sure we arent reassigning ourself // e.g. thisQueue = thisQueue. if(this != &q) { this->~Queue(); if(q.empty()) { myFront = myBack = NULL; } else { myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } return *this; } private: class Node { public: T data; Node * next; Node(T value, Node * first = 0) : data(value), next(first) {} }; typedef Node * NodePointer; NodePointer myFront, myBack, queueSize; }; /*------------------------------------------------------------------------ join Preconditions: requires 2 queue values Postconditions: appends queue2 to the end of queue1 description: this function joins 2 queues into 1. ------------------------------------------------------------------------*/ template <typename T> Queue<T> join(Queue<T> q1, Queue<T> q2) { Queue<T> q1Copy(q1), q2Copy(q2); Queue<T> jQueue; while(!q1Copy.empty()) { jQueue.enqueue(q1Copy.front()); q1Copy.dequeue(); } while(!q2Copy.empty()) { jQueue.enqueue(q2Copy.front()); q2Copy.dequeue(); } cout << jQueue << endl; return jQueue; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a Queue of type T Postconditions: returns the ostream (for chaining) description: this function is overloaded for outputing a queue with << ----------------------------------------------------------------------------*/ template <typename T> ostream & operator<<(ostream &out, Queue<T> &s) { s.display(out); return out; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of type Student Postconditions: none description: this function is overloaded for outputing an object of type Student. ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, Student &s) { s.display(out); } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of a pointer to a Student object. Postconditions: none description: this function is overloaded for outputing pointers to Students ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, StudentPointer &s) { s->display(out); } #endif Now I'm having some issues with it. For one, when I add 0 to a queue and then I output the queue like so.. Queue<double> qdub; qdub.enqueue(0); cout << qdub << endl; That works, it will output 0. But for example, if I modify that queue in any way.. like.. assign it to a different queue.. Queue<double> qdub1; Queue<double> qdub2; qdub1.enqueue(0; qdub2 = qdub1; cout << qdub2 << endl; It will give me weird values for 0 like.. 7.86914e-316. Help on this would be much appreciated!

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• Plotting an Arc in Discrete Steps

  - by phobos51594

  Good afternoon, Background My question relates to the plotting of an arbitrary arc in space using discrete steps. It is unique, however, in that I am not drawing to a canvas in the typical sense. The firmware I am designing is for a gcode interpreter for a CNC mill that will translate commands into stepper motor movements. Now, I have already found a similar question on this very site, but the methodology suggested (Bresenham's Algorithm) appears to be incompatable for moving an object in space, as it only relies on the calculation of one octant of a circle which is then mirrored about the remaining axes of symmetry. Furthermore, the prescribed method of calculation an arc between two arbitrary angles relies on trigonometry (I am implementing on a microcontroller and would like to avoid costly trig functions, if possible) and simply not taking the steps that are out of the range. Finally, the algorithm only is designed to work in one rotational direction (e.g. counterclockwise). Question So, on to the actual question: Does anyone know of a general-purpose algorithm that can be used to "draw" an arbitrary arc in discrete steps while still giving respect to angular direction (CW / CCW)? The final implementation will be done in C, but the language for the purpose of the question is irrelevant. Thank you in advance. References S.O post on drawing a simple circle using Bresenham's Algorithm: "Drawing" an arc in discrete x-y steps Wiki page describing Bresenham's Algorithm for a circle http://en.wikipedia.org/wiki/Midpoint_circle_algorithm Gcode instructions to be implemented (see. G2 and G3) http://linuxcnc.org/docs/html/gcode.html

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• Are there pitfalls to using static class/event as an application message bus

  - by Doug Clutter

  I have a static generic class that helps me move events around with very little overhead: public static class MessageBus<T> where T : EventArgs { public static event EventHandler<T> MessageReceived; public static void SendMessage(object sender, T message) { if (MessageReceived != null) MessageReceived(sender, message); } } To create a system-wide message bus, I simply need to define an EventArgs class to pass around any arbitrary bits of information: class MyEventArgs : EventArgs { public string Message { get; set; } } Anywhere I'm interested in this event, I just wire up a handler: MessageBus<MyEventArgs>.MessageReceived += (s,e) => DoSomething(); Likewise, triggering the event is just as easy: MessageBus<MyEventArgs>.SendMessage(this, new MyEventArgs() {Message="hi mom"}); Using MessageBus and a custom EventArgs class lets me have an application wide message sink for a specific type of message. This comes in handy when you have several forms that, for example, display customer information and maybe a couple forms that update that information. None of the forms know about each other and none of them need to be wired to a static "super class". I have a couple questions: fxCop complains about using static methods with generics, but this is exactly what I'm after here. I want there to be exactly one MessageBus for each type of message handled. Using a static with a generic saves me from writing all the code that would maintain the list of MessageBus objects. Are the listening objects being kept "alive" via the MessageReceived event? For instance, perhaps I have this code in a Form.Load event: MessageBus<CustomerChangedEventArgs>.MessageReceived += (s,e) => DoReload(); When the Form is Closed, is the Form being retained in memory because MessageReceived has a reference to its DoReload method? Should I be removing the reference when the form closes: MessageBus<CustomerChangedEventArgs>.MessageReceived -= (s,e) => DoReload();

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• Convert date to string upon saving a doctrine record

  - by takteek

  Hi, I'm trying to migrate one of my PHP projects to Doctrine. I've never used it before so there are a few things I don't understand. In my current code, I have a class similar to this: class ScheduleItem { private Date start; //A PEAR Date object. private Date end; public function getStart() { return $this-start; } public function setStart($val) { $this-start = $val; } public function getEnd() { return $this-end; } public function setEnd($val) { $this-end= $val; } } I have a ScheduleItemDAO class with methods like save(), getByID(), etc. When loading from and saving to the database, the DAO class converts the Date objects to and from strings so they can be stored in a timestamp field. In my attempt to move to Doctrine, I created a new class like this: class ScheduleItem extends Doctrine_Record { public function setTableDefinition() { $this-hasColumn('start', 'timestamp'); $this-hasColumn('end', 'timestamp'); } } I had hoped I would be able to use Date objects for the start and end times, and have them converted to strings when they are saved to the database. How can I accomplish this?

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• Detecting one point's location compared to two other points.

  - by WizardOfOdds

  Hi all, you can check my profile, this is not homework. I've got an interesting little problem to solve in a very real software and I'm looking for an easy way to solve it. I've got two fixed points on screen (they're fixed, but I don't know beforehand their position) that are not at the same location. These two fixed points form an imaginary line. Now I've got a third point that is "on one side" of that line (it cannot be on the line). The user can grab the point (the user actually grab an object, whose I track by its center, which is the point I'm interested in) and drag it. But it cannot "cross" the imaginary line. What is the easiest way to detect if the user is crossing the imaginary line? Example: a c / / (c cannot be dragged here) / b Or: c b -------------- a (c cannot be dragged here) So what is an easy to detect if c is staying on the correct "side" of the line (I draw segments here, but it really can be thought of as a line). One way to detect this is to take the destination point d and see if segment (c,d) intersects with line (a,b), but isn't there an easier way? Can't I just do some 2D dot-product magic here and have basically a one or two liner solving my issue?

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• Semantically linking to code snippets

  - by Tim

  What's the most simple and semantic way of presenting code snippets in HTML? Possible XHTML syntax <a href="code_sample.php" type="text/x-php"> Example of widget creation </a> Example of linked file (code_sample.php): // Create a new widget $widget = new widget(); Pros: Semantically uses title to describe the source code being referenced Up to the client to render snippet Having very many custom server-side implementations tells me it should be standardized Browsers can have plug-ins for copy+paste, download, etc Seems to me this is where it belongs (not in Javascript) Degradation: non-compliant browsers receive a link to the associated content Cons: Not semantic enough? Seems wrong to replace hyperlinks with source code for presentation <object> might be better, but wouldn't degrade as nicely. Background I'm trying to create a "personal" XHTML standard for storing notes (wow, this is probably among the nerdiest things I've said). Since notes are just "scratch" it needs to be very lightweight. SO's markdown is very lightweight but not semantic enough for my needs. Plus, now I'm just curious. What's the most ideal syntax for linking to client-rendered code-snippets?

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• Jquery click bindings are not working correctly when binding multiple copies

  - by KallDrexx

  I seem to have an issue when creating copies of a template and tying the .click() method to them properly. Take the following javascript for example: var list; // Loop through all of the objects var topics = data.objects; for (x = 0; x < objects.length; x++) { // Clone the object list item template var item = $("#object_item_list_template").clone(); // Setup the click action and inner text for the link tag in the template var objectVal = objects[x].Value; item.find('a').click(function () { ShowObject(objectVal.valueOf(), 'T'); }).html(objects[x].Text); // add the html to the list if (list == undefined) list = item; else list.append(item.contents()); } // Prepend the topics to the topic list $("#object_list").empty().append(list.contents()); The problem I am seeing with this is that no matter which item the user clicks on in the #object_list, ShowObject() is called with the last value of objectVal. So for example, if the 3rd item's <a> is clicked, ShowObject(5,'T'); is called even though objects[2].Value is successfully being seen as 2. How can I get this to work? The main purpose of this code is to take a variable number of items gotten from a JSON AJAX request, make copies of the item template, and insert those copies into the correct spot on the html page. I decided to do it this way so that I can keep all my HTML in one spot for when I need to change the layout or design of the page, and not have to hunt for the html code in the javascript.

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• First test of a Windows Phone application

  - by Maurizio Reginelli

  I downloaded the Microsoft Visual Studio 2010 Express for Windows Phone and I wrote a simple application to make a first test of the emulator. In this application I have only a button with the property Content binded to a string called ButtonText and with the property Background binded to a SolidColorBrush named FillColor. I handled the Click event with this code: void MyButton_Click(object sender, RoutedEventArgs e) { if (toggle == true) { ButtonText = "Blue"; FillColor = new SolidColorBrush(Colors.Blue); } else { ButtonText = "Red"; FillColor = new SolidColorBrush(Colors.Red); } toggle = !toggle; } Unfortunately this doesn't work. While the Content of the Button changes each time the button is pressed, I cannot say the same for the Background which remains at the same color. Could you tell me what is wrong? Thank you. I also post the XAML: <Grid x:Name="ContentGrid" Grid.Row="1"> <Button Name="MyButton" Width="300" Height="300" Content="{Binding Path=ButtonText}" Background="{Binding Path=FillColor}" /> </Grid>

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• Why can't I pass self as a named argument to an instance method in Python?

  - by Joseph Garvin

  This works: >>> def bar(x, y): ... print x, y ... >>> bar(y=3, x=1) 1 3 And this works: >>> class foo(object): ... def bar(self, x, y): ... print x, y ... >>> z = foo() >>> z.bar(y=3, x=1) 1 3 And even this works: >>> foo.bar(z, y=3, x=1) 1 3 But why doesn't this work? >>> foo.bar(self=z, y=3, x=1) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unbound method bar() must be called with foo instance as first argument (got nothing instead) This makes metaprogramming more difficult, because it requires special case handling. I'm curious if it's somehow necessary by Python's semantics or just an artifact of implementation.

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• JAXB, how to marshal without a namespace

  - by Alvin

  I have a fairly large repetitive XML to create using JAXB. Storing the whole object in the memory then do the marshaling takes too much memory. Essentially, my XML looks like this: <Store> <item /> <item /> <item /> ..... </Store> Currently my solution to the problem is to "hard code" the root tag to an output stream, and marshal each of the repetitive element one by one: aOutputStream.write("<?xml version="1.0"?>") aOutputStream.write("<Store>") foreach items as item aMarshaller.marshall(item, aOutputStream) end aOutputStream.write("</Store>") aOutputStream.close() Somehow the JAXB generate the XML like this <Store xmlns="http://stackoverflow.com"> <item xmlns="http://stackoverflow.com"/> <item xmlns="http://stackoverflow.com"/> <item xmlns="http://stackoverflow.com"/> ..... </Store> Although this is a valid XML, but it just look ugly, so I'm wonder is there any way to tell the marshaller not to put namespace for the item elements? Or is there better way to use JAXB to serialize to XML chunk by chunk?

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• ExpertPDF and Caching of URLs

  - by Josh

  We are using ExpertPDF to take URLs and turn them into PDFs. Everything we do is through memory, so we build up the request and then read the stream into ExpertPDF and then write the bits to file. All the files we have been requesting so far are just plain HTML documents. Our designers update CSS files or change the HTML and rerequest the documents as PDFs, but often times, things are getting cached. Take, for example, if I rename the only CSS file and view the HTML page through a web browser, the page looks broke because the CSS doesn't exist. But if I request that page through the PDF Generator, it still looks ok, which means somewhere the CSS is cached. Here's the relevant PDF creation code: // Create a request HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url); request.UserAgent = "IE 8.0"; request.ContentType = "application/x-www-form-urlencoded"; request.Method = "GET"; // Send the request HttpWebResponse resp = (HttpWebResponse)request.GetResponse(); if (resp.IsFromCache) { System.Web.HttpContext.Current.Trace.Write("FROM THE CACHE!!!"); } else { System.Web.HttpContext.Current.Trace.Write("not from cache"); } // Read the response pdf.SavePdfFromHtmlStream(resp.GetResponseStream(), System.Text.Encoding.UTF8, "Output.pdf"); When I check the trace file, nothing is being loaded from cache. I checked the IIS log file and found a 200 response coming from the request, even after a file had been updated (I would expect a 302). We've tried putting the No-Cache attribute on all HTML pages, but still no luck. I even turned off all caching at the IIS level. Is there anything in ExpertPDF that might be caching somewhere or something I can do to the request object to do a hard refresh of all resources? UPDATE I put ?foo at the end of my style href links and this updates the CSS everytime. Is there a setting someplace that can prevent stylesheets from being cached so I don't have to do this inelegant solution?

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