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• Normalizing Item Names & Synonyms

  - by RabidFire

  Consider an e-commerce application with multiple stores. Each store owner can edit the item catalog of his store. My current database schema is as follows: item_names: id | name | description | picture | common(BOOL) items: id | item_name_id | picture | price | description | picture item_synonyms: id | item_name_id | name | error(BOOL) Notes: error indicates a wrong spelling (eg. "Ericson"). description and picture of the item_names table are "globals" that can optionally be overridden by "local" description and picture fields of the items table (in case the store owner wants to supply a different picture for an item). common helps separate unique item names ("Jimmy Joe's Cheese Pizza" from "Cheese Pizza") I think the bright side of this schema is: Optimized searching & Handling Synonyms: I can query the item_names & item_synonyms tables using name LIKE %QUERY% and obtain the list of item_name_ids that need to be joined with the items table. (Examples of synonyms: "Sony Ericsson", "Sony Ericson", "X10", "X 10") Autocompletion: Again, a simple query to the item_names table. I can avoid the usage of DISTINCT and it minimizes number of variations ("Sony Ericsson Xperia™ X10", "Sony Ericsson - Xperia X10", "Xperia X10, Sony Ericsson") The down side would be: Overhead: When inserting an item, I query item_names to see if this name already exists. If not, I create a new entry. When deleting an item, I count the number of entries with the same name. If this is the only item with that name, I delete the entry from the item_names table (just to keep things clean; accounts for possible erroneous submissions). And updating is the combination of both. Weird Item Names: Store owners sometimes use sentences like "Harry Potter 1, 2 Books + CDs + Magic Hat". There's something off about having so much overhead to accommodate cases like this. This would perhaps be the prime reason I'm tempted to go for a schema like this: items: id | name | picture | price | description | picture (... with item_names and item_synonyms as utility tables that I could query) Is there a better schema you would suggested? Should item names be normalized for autocomplete? Is this probably what Facebook does for "School", "City" entries? Is the first schema or the second better/optimal for search? Thanks in advance! References: (1) Is normalizing a person's name going too far?, (2) Avoiding DISTINCT

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• Should I add try/catch around when casting on an attribute of JSP implicit object?

  - by Michael Mao

  Hi all: Basically what I mean is like this: List<String[]> routes = (List<String[]>)application.getAttribute("routes"); For the above code, it tries to get an attribute named "routes" from the JSP implicit object - application. But as everyone knows, after this line of code, routes may very well contains a null - which means this application hasn't got an attribute named "routes". Is this "casting on null" good programming practice in Java or not? Basically I try to avoid exceptions such as java.io.InvalidCastException I reckon things like this are more as "heritage" of Java 1.4 when generic types were not introduced to this language. So I guess everything stored in application attributes as Objects (Similar to traditional ArrayList). And when you do "downcast", there might be invalid casts. What would you do in this case? Update: Just found that although in the implicit object application I did store a List of String arrays, when I do this : List<double[]> routes = (List<double[]>)application.getAttribute("routes"); It doesn't produce any error... And I felt not comfortable already... And even with this code: out.print(routes.get(0)); It does print out something strange : [Ljava.lang.String;@18b352f Am I printing a "pointer to String"? I can finally get an exception like this: out.print(routes.get(0)[1]); with error : java.lang.ClassCastException: [Ljava.lang.String; Because it was me to add the application attribute, I know which type should it be cast to. I feel this is not "good enough", what if I forget the exact type? I know there are still some cases where this sort of thing would happen, such as in JSP/Servlet when you do casting on session attributes. Is there a better way to do this? Before you say:"OMG, why you don't use Servlets???", I should justify my reason as this: - because my uni sucks, its server can only work with Servlets generated by JSP, and I don't really want to learn how to fix issues like that. look at my previous question on this , and this is uni homework, so I've got no other choice, forget all about war, WEB-INF,etc, but "code everything directly into JSP" - because the professors do that too. :)

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• How to update NSMutableDictionary. My code doesn't work.

  - by dawatson833

  I've populated an array using. arrSettings = [[NSMutableArray alloc] initWithContentsOfFile:[self settingsPath]]; The file is a plist with the root as an array and then a dictionary with three three keys defined as number. I've also tried setting the keys to string. I display the values in the plist file on a view using. diaper = [[arrSettings objectAtIndex:0] objectForKey:@"Diaper Expenses"]; oil = [[arrSettings objectAtIndex:0] objectForKey:@"Oil Used"]; tree = [[arrSettings objectAtIndex:0] objectForKey:@"Wood Used"]; This code works fine, the values in the dictionary are assigned to the variables and they are displayed. The user can make changes and then press a save button. I use this code to extract the dictionary part of the array so I can update it. The assignment to editDictionary works. I've double checked the key names including case and that is correct. editDictionary = [[NSMutableDictionary alloc] init]; editDictionary = [arrSettings objectAtIndex:0]; NSNumber *myNumber = [NSNumber numberWithFloat:diaperAmount]; [editDictionary setValue:myNumber forKey:@"Diaper Expenses"]; myNumber = [NSNumber numberWithFloat:oilAmount]; [editDictionary setValue:myNumber forKey:@"Oil Used"]; myNumber = [NSNumber numberWithFloat:treeAmount]; [editDictionary setValue:myNumber forKey:@"Wood Used"]; In this example I've used a nsnumber. But I've also tried the xxxAmount field as part of SetValue instead of creating a NSNumber. Neither implementation works. Several strange things happen. Sometimes the first two setvalue statements work, but the last setvalue fails with a EXC_BAD_ACCESS failure. Other times the first setValue fails with the same error. I have no idea why the first two sometimes work. I'm at a loss of what to do next. I've tried several implentations and none of them work. Also, in the debugger how can I display the editDictionary elements. I can see editDictionary, but I don't know how to display the individual elements.

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• Using empty row as default in a ComboBox with Style "DropDownList"?

  - by Pesche Helfer

  Hi board I am trying to write a method, that takes a ComboBox, a DataTable and a TextBox as arguments. The purpose of it is to filter the members displayed in the ComboBox according to the TextBox.Text. The DataTable contains the entire list of possible entries that will then be filtered. For filtering, I create a DataView of the DataTable, add a RowFilter and then bind this View to the ComboBox as DataSource. To prevent the user from typing into the ComboBox, I choose the DropDownStyle DropDownList. That’s working fine so far, except that the user should also be able to choose nothing / empty line. In fact, this should be the default member to be displayed (to prevent choosing a wrong member by accident, if the user clicks through the dialog too fast). I tried to solve this problem by adding a new Row to the view. While this works for some cases, the main issue here is that any DataTable can be passed to the method. If the DataTable contains columns that cannot be null and don’t contain a default value, I suppose I will raise an error by adding an empty row. A possibility would be to create a view that contains only the column that is defined as DisplayMember, and the one that is defined as ValueMember. Alas, this can’t be done with a view in C#. I would like to avoid creating a true copy of the DataTable at all cost, since who knows how big it will get with time. Do you have any suggestions how to get around this problem? Instead of a view, could I create an object containing two members and assign the DisplayMember and the ValueMember to these members? Would the members be passed as reference (what I hope) or would true copied be created (in which case it would not be a solution)? Thank you very much for your help! Best regards public static void ComboFilter(ComboBox cb, DataTable dtSource, TextBox filterTextBox) { cb.DropDownStyle = ComboBoxStyle.DropDownList; string displayMember = cb.DisplayMember; DataView filterView = new DataView(dtSource); filterView.AddNew(); filterView.RowFilter = displayMember + " LIKE '%" + filterTextBox.Text + "%'"; cb.DataSource = filterView; }

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• C# Property Access vs Interface Implementation

  - by ehdv

  I'm writing a class to represent a Pivot Collection, the root object recognized by Pivot. A Collection has several attributes, a list of facet categories (each represented by a FacetCategory object) and a list of items (each represented by a PivotItem object). Therefore, an extremely simplified Collection reads: public class Collection { private List<FacetCategory> categories; private List<PivotItem> items; // other attributes } What I'm unsure of is how to properly grant access to those two lists. Because declaration order of both facet categories and items is visible to the user, I can't use sets, but the class also shouldn't allow duplicate categories or items. Furthermore, I'd like to make the Collection object as easy to use as possible. So my choices are: Have Collection implement IList<PivotItem> and have accessor methods for FacetCategory: In this case, one would add an item to Collection foo by writing foo.Add(bar). This works, but since a Collection is equally both kinds of list making it only pass as a list for one type (category or item) seems like a subpar solution. Create nested wrapper classes for List (CategoryList and ItemList). This has the advantage of making a consistent interface but the downside is that these properties would no longer be able to serve as lists (because I need to override the non-virtual Add method I have to implement IList rather than subclass List. Implicit casting wouldn't work because that would return the Add method to its normal behavior. Also, for reasons I can't figure out, IList is missing an AddRange method... public class Collection { private class CategoryList: IList<FacetCategory> { // ... } private readonly CategoryList categories = new CategoryList(); private readonly ItemList items = new ItemList(); public CategoryList FacetCategories { get { return categories; } set { categories.Clear(); categories.AddRange(value); } } public ItemList Items { get { return items; } set { items.Clear(); items.AddRange(value); } } } Finally, the third option is to combine options one and two, so that Collection implements IList<PivotItem> and has a property FacetCategories. Question: Which of these three is most appropriate, and why?

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• .NET: Is there a way to finagle a default namespace in an XPath 1.0 query?

  - by Cheeso

  I'm building a tool that performs xpath 1.0 queries on XHTML documents. The requirement to use a namespace prefix in the query is killing me. The query looks like this: html/body/div[@class='contents']/div[@class='body']/ div[@class='pgdbbyauthor']/h2[a[@name][starts-with(.,'Quick')]]/ following-sibling::ul[1]/li/a (all on one line) ...which is bad enough, except because it's xpath 1.0, I need to use an explicit namespace prefix on each QName, so it looks like this: ns1:html/ns1:body/ns1:div[@class='contents']/ns1:div[@class='body']/ ns1:div[@class='pgdbbyauthor']/ns1:h2[ns1:a[@name][starts-with(.,'Quick')]]/ following-sibling::ns1:ul[1]/ns1:li/ns1:a To set up the query, I do something like this: var xpathDoc = new XPathDocument(new StringReader(theText)); var nav = xpathDoc.CreateNavigator(); var xmlns = new XmlNamespaceManager(nav.NameTable); foreach (string prefix in xmlNamespaces.Keys) xmlns.AddNamespace(prefix, xmlNamespaces[prefix]); XPathNodeIterator selection = nav.Select(xpathExpression, xmlns); But what I want is for the xpathExpression to use the implicit default namespace. Is there a way for me to transform the unadorned xpath expression, after it's been written, to inject a namespace prefix for each element name in the query? I'm thinking, anything between two slashes, I could inject a prefix there. Excepting of course axis names like "parent::" and "preceding-sibling::" . And wildcards. That's what I mean by "finagle a default namespace". Is this hack gonna work? Addendum Here's what I mean. suppose I have an xpath expression, and before passing it to nav.Select(), I transform it. Something like this: string FixupWithDefaultNamespace(string expr) { string s = expr; s = Regex.Replace(s, "^(?!::)([^/:]+)(?=/)", "ns1:$1"); // beginning s = Regex.Replace(s, "/([^/:]+)(?=/)", "/ns1:$1"); // stanza s = Regex.Replace(s, "::([A-Za-z][^/:*]*)(?=/)", "::ns1:$1"); // axis specifier s = Regex.Replace(s, "\\[([A-Za-z][^/:*\\(]*)(?=[\\[\\]])", "[ns1:$1"); // predicate s = Regex.Replace(s, "/([A-Za-z][^/:]*)(?!<::)$", "/ns1:$1"); // end s = Regex.Replace(s, "^([A-Za-z][^/:]*)$", "ns1:$1"); // edge case s = Regex.Replace(s, "([-A-Za-z]+)\\(([^/:\\.,\\)]+)(?=[,\\)])", "$1(ns1:$2"); // xpath functions return s; } This actually works for simple cases I tried. To use the example from above - if the input is the first xpath expression, the output I get is the 2nd one, with all the ns1 prefixes. The real question is, is it hopeless to expect this Regex.Replace approach to work, as the xpath expressions get more complicated?

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• Passing objects to a UITypeEditor

  - by Kath

  I am currently hoping to use a PropertyGrid to allow users to edit some of my classes, however I've hit a wall with passing objects to the UITypeEditor(s) they use. When the user presses the drop down I want to show a listbox of already loaded textures to choose from, if they want to use a texture the application hasn't loaded yet they can click a button to choose one from a file dialog. In case I make no sense here a mock of the form: . My problem: To fill the listbox I need access to the class that manages the list of resources from the UITypeEditor. Now I've solved this problem for my own classes by giving them a reference on creation to their managing object. In the UITypeEditor I then use that reference to access what I need. However I can't do this for classes I haven't written, such as the XNA Texture2D class. Here are what the classes I'm using look like: class StaticGeometryChunk { // Geometry data to draw with. Contains a reference to its managing // class for use in its UITypeEditor. public GeometryData { get; set; } .... } class Material { // These are XNA classes. I can't just add a reference to its managing // class (I think?). public Texture2D Texture1 { get; set; } public Texture2D Texture2 { get; set; } .... } I've been looking at my options and they seem to be: Make the managing classes static. I don't really want to do this. There are several managing classes as each resource is loaded differently. There are also classes that need to be created before these and are passed in. Make the managing classes singletons. I don't really want to do this either. It seems like a quick and dirty way to "hide" the problem instead of "solve" it. I also might want the option of having several managing classes in the future which the singletons eliminate. Create a wrapper class which holds the reference to a managing class and its target (such as the XNA Texture2D). This is currently what I'm thinking of doing. Its would be quite simple and quick to do but something about it nags me but I don't know what. Any thoughts on the above or other methods to pass what I need into the UITypeEditor? Thank you for reading.

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• Error implementing Dynamic Tab with ListView within each Tab - Tabs don't show up

  - by Jon

  I am trying to create a dyanmic tab application that has tabs on the left for each type of Food (e.g. Pasta, Dairy, etc. including those dynamically defined by user) and for each tab, have a listview connected to a SQLite database that updates. This is in the onCreate method: setContentView(R.layout.foodCabinet_layout); dbHelper = new FoodStorageDBHelper(this); dbHelper.open(); Cursor foodTypes = dbHelper.getAllFoodTypes(); ArrayList<String> typeOfFood = new ArrayList<String>(); typeOfFoods.add(foodTypes.getString(1)); while(foodTypes.moveToNext()){ typeOfFoods.add(foodTypes.getString(1)); } final TabHost tbh = (TabHost)findViewById(R.id.food_tabhost_cabinet); tbh.setup(); for(final String s : typeOfFood){ TabSpec nts = tbh.newTabSpec(s); nts.setIndicator(s.replace('_', ' ')); nts.setContent(new TabHost.TabContentFactory(){ public View createTabContent(String tag) { ListView foodCabinetLV = new ListView(FoodCabinet.this); Cursor mCursor = dbHelper.getAllFoodsWithType(s); // Create an array to specify the fields we want to display in the list (only TITLE) String[] from = new String[]{FoodStorageDBHelper.KEY_NAME, FoodStorageDBHelper.KEY_YEAR,FoodStorageDBHelper.KEY_RANK}; // and an array of the fields we want to bind those fields to (in this case just text1) int[] to = new int[]{R.id.childname,R.id.childyear,R.id.childrank}; // Now create a simple cursor adapter and set it to display SimpleCursorAdapter notes = new SimpleCursorAdapter(FoodCabinet.this, R.layout.food_row, mCursor, from, to); foodCabinetLV.setAdapter(notes); startManagingCursor(mCursor); foodCabinetLV.setOnItemClickListener( new AdapterView.OnItemClickListener() { public void onItemClick(AdapterView arg0, View arg1, int arg2, long arg3) { Intent i = new Intent(); i.setClass(arg0.getContext(), EditFoodDialog.class); i.putExtra(FoodStorageDBHelper.KEY_ROWID, Long.toString(arg3)); startActivityForResult(i, LoadFoodOrganizer.ACTIVITY_EDIT); } }); return foodCabinetLV; } }); } For some reason, it doesn't show anything... it's a blank screen. Any help would be very much appreciated. Let me know! Thanks! Jon

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• How to efficently build an interpreter (lexer+parser) in C?

  - by Rizo

  I'm trying to make a meta-language for writing markup code (such as xml and html) wich can be directly embedded into C/C++ code. Here is a simple sample written in this language, I call it WDI (Web Development Interface): /* * Simple wdi/html sample source code */ #include <mySite> string name = "myName"; string toCapital(string str); html { head { title { mySiteTitle; } link(rel="stylesheet", href="style.css"); } body(id="default") { // Page content wrapper div(id="wrapper", class="some_class") { h1 { "Hello, " + toCapital(name) + "!"; } // Lists post ul(id="post_list") { for(post in posts) { li { a(href=post.getID()) { post.tilte; } } } } } } } Basically it is a C source with a user-friendly interface for html. As you can see the traditional tag-based style is substituted by C-like, with blocks delimited by curly braces. I need to build an interpreter to translate this code to html and posteriorly insert it into C, so that it can be compiled. The C part stays intact. Inside the wdi source it is not necessary to use prints, every return statement will be used for output (in printf function). The program's output will be clean html code. So, for example a heading 1 tag would be transformed like this: h1 { "Hello, " + toCapital(name) + "!"; } // would become: printf("<h1>Hello, %s!</h1>", toCapital(name)); My main goal is to create an interpreter to translate wdi source to html like this: tag(attributes) {content} = <tag attributes>content</tag> Secondly, html code returned by the interpreter has to be inserted into C code with printfs. Variables and functions that occur inside wdi should also be sorted in order to use them as printf parameters (the case of toCapital(name) in sample source). I am searching for efficient (I want to create a fast parser) way to create a lexer and parser for wdi. Already tried flex and bison, but as I am not sure if they are the best tools. Are there any good alternatives? What is the best way to create such an interpreter? Can you advise some brief literature on this issue?

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• asp.net mvc & jquery dialog: What approach do I take to add items to a dropdownlist/select list with

  - by Mark Redman

  Hi, I am new to MVC and have a grasp of the basic model, but still doing everything with postbacks etc. One aspect of the UI I want to build is to have a drop-down-list of items with a button to add an item to the database and refresh the list. Achieving this with WebForms was straight forward as everything was wrapped in UpdatePanels, but what is the best approach to achieve this using MVC? Part of the markup for the list and button look like this: <table> <tr> <td><%=Html.DropDownList("JobTitleSelectList", Model.JobTitleSelectList, "(select job title)", new { @class = "data-entry-field" })%></td> <td>&nbsp;</td> <td><a id="AddJobTitleDialogLink" href="javascript: addJobTitleDialog();" title="Add Job Title"><img id="AddJobTitleButtonImage" src="/Content/Images/Icons/16x16/PlusGrey.png" border="0" /></a></td> </tr> </table> The Dialog is a standard jquery Ui dialog, looks like this: <div id="SingleTextEntryDialog" style="display:none"> <table> <tr> <td>Name:</td> <td><input id="SingleTextEntryDialogText" type="text" size="25" /></td> </tr> </table> </div> I am guessing I need to put this into a UserControl / PartialView (are they the same thing?) Also with the strongly typed View how do I pass the Model or just the SelectList Property to the UserControl or is this not the case? Nor sure if there should be form in the dialog div? or how that is going to postback via ajax. Some examples show a lot of ajax code in the page something like: $.ajax({...}); I assume doing this using jquery is more code than asp.net webforms, but there is just more code to see doing a "View Source" on a page? Your comments appreciated.

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• SQL/Schema comparison and upgrade

  - by Workshop Alex

  I have a simple situation. A large organisation is using several different versions of some (desktop) application and each version has it's own database structure. There are about 200 offices and each office will have it's own version, which can be one of 7 different ones. The company wants to upgrade all applications to the latest versions, which will be version 8. The problem is that they don't have a separate database for each version. Nor do they have a separate database for each office. They have one single database which is handled by a dedicated server, thus keeping things like management and backups easier. Every office has it's own database schema and within the schema there's the whole database structure for their specific application version. As a result, I'm dealing with 200 different schema's which need to be upgraded, each with 7 possible versions. Fortunately, every schema knows the proper version so checking the version isn't difficult. But my problem is that I need to create upgrade scripts which can upgrade from version 1 to version 2 to version 3 to etc... Basically, all schema's need to be bumped up one version until they're all version 8. Writing the code that will do this is no problem. the challenge is how to create the upgrade script from one version to the other? Preferably with some automated tool. I've examined RedGate's SQL Compare and Altova's DatabaseSpy but they're not practical. Altova is way too slow. RedGate requires too much processing afterwards, since the generated SQL Script still has a few errors and it refers to the schema name. Furthermore, the code needs to become part of a stored procedure and the code generated by RedGate doesn't really fit inside a single procedure. (Plus, it's doing too much transaction-handling, while I need everything within a single transaction. I have been considering using another SQL Comparison tool but it seems to me that my case is just too different from what standard tools can deliver. So I'm going to write my own comparison tool. To do this, I'll be using ADOX with Delphi to read the catalogues for every schema version in the database, then use this to write the SQL Statements that will need to upgrade these schema's to their next version. (Comparing 1 with 2, 2 with 3, 3 with 4, etc.) I'm not unfamiliar with generating SQL-Script-Generators so I don't expect too many problems. And I'll only be upgrading the table structures, not any of the other database objects. So, does anyone have some good tips and tricks to apply when doing this kind of comparisons? Things to be aware of? Practical tips to increase speed?

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• Java program has errors, 80 lines of code

  - by user2961687

  I have a problem with a program. It contains a lot of errors in Eclipse. Sorry for my english and thank you in advance. Here is the task: I. Declare a class that contains private fields Jam: String taste, double weight Create constructors containing variables as parameters: (String taste, double weight), (double weight), (String taste). Parameters constructors should initialize class fields. In case the constructor does not provide the necessary parameter, it must be assumed that the field taste must have the value "No Name" and weight - 100.0. Introduce the use of all constructors creating objects that represent three kinds of jams. Note: it must be assumed that the only constructor with two parameters can be assigned to fields of the class. Declare a class Jar that contains the field Jam jam, a dedicated constructor initiating all declared fields and methods: open close isItOpen Next, create an object of class Jar and fill it with the selected type of jam, operations repeat for all the kinds of jams. This is my code this far: public class App { public static void main(String[] args) { Jam strawberry = new Jam("strawberry", 20.45); Jam raspberry = new Jam(40.50); Jam peach = new Jam("peach"); Jar jar_1 = new Jar(); Jar jar_2 = new Jar(); Jar jar_3 = new Jar(); jar_1.open(); jar_1.fillIn(strawberry); jar_2.fillIn(peach); jar_3.fillIn(raspberry); } } class Jam { String taste; double weight; public Jam(String taste, double weight) { this.taste = taste; this.weight = weight; } public Jam(double weight) { this.taste = "No name"; this.weight = weight; } public Jam(String taste) { this.taste = taste; this.weight = 100.0; } } class Jar { public Jam Jam = new Jam(); private String state_jar; public Jar() { Jam.weight = 0; Jam.taste = ""; state_jar = "closed"; } public static String open() { state_jar = open; return state_jar; } public static String close() { state_jar = "closed"; return state_jar; } public static boolean isItOpen() { return state_jar; } public void fillIn(Jam jam) { if (isItOpen == false) open(); this.Jam.weight = jam.weight; this.Jam.taste = jam.taste; this.Jam.close(); } }

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• Windows splash screen using GDI+

  - by Luther

  The eventual aim of this is to have a splash screen in windows that uses transparency but that's not what I'm stuck on at the moment. In order to create a transparent window, I'm first trying to composite the splash screen and text on an off screen buffer using GDI+. At the moment I'm just trying to composite the buffer and display it in response to a 'WM_PAINT' message. This isn't working out at the moment; all I see is a black window. I imagine I've misunderstood something with regards to setting up render targets in GDI+ and then rendering them (I'm trying to render the screen using straight forward GDI blit) Anyway, here's the code so far: //my window initialisation code void MyWindow::create_hwnd(HINSTANCE instance, const SIZE &dim) { DWORD ex_style = WS_EX_LAYERED ; //eventually I'll be making use of this layerd flag m_hwnd = CreateWindowEx( ex_style, szFloatingWindowClass , L"", WS_POPUP , 0, 0, dim.cx, dim.cy, null, null, instance, null); SetWindowLongPtr(m_hwnd ,0, (__int3264)(LONG_PTR)this); m_display_dc = GetDC(NULL); //This was sanity check test code - just loading a standard HBITMAP and displaying it in WM_PAINT. It worked fine //HANDLE handle= LoadImage(NULL , L"c:\\test_image2.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE); m_gdip_offscreen_bm = new Gdiplus::Bitmap(dim.cx, dim.cy); m_gdi_dc = Gdiplus::Graphics::FromImage(m_gdip_offscreen_bm);//new Gdiplus::Graphics(m_splash_dc );//window_dc ;m_splash_dc //this draws the conents of my splash screen - this works if I create a GDI+ context for the window, rather than for an offscreen bitmap. //For all I know, it might actually be working but when I try to display the contents on screen, it shows a black image draw_all(); //this is just to show that drawing something simple on the offscreen bit map seems to have no effect Gdiplus::Pen pen(Gdiplus::Color(255, 0, 0, 255)); m_gdi_dc->DrawLine(&pen, 0,0,100,100); DWORD last_error = GetLastError(); //returns '0' at this stage } And here's the snipit that handles the WM_PAINT message: ---8<----------------------- //Paint message snippit case WM_PAINT: { BITMAP bm; PAINTSTRUCT ps; HDC hdc = BeginPaint(vg->m_hwnd, &ps); //get the HWNDs DC HDC hdcMem = vg->m_gdi_dc->GetHDC(); //get the HDC from our offscreen GDI+ object unsigned int width = vg->m_gdip_offscreen_bm->GetWidth(); //width and height seem fine at this point unsigned int height = vg->m_gdip_offscreen_bm->GetHeight(); BitBlt(hdc, 0, 0, width, height, hdcMem, 0, 0, SRCCOPY); //this blits a black rectangle DWORD last_error = GetLastError(); //this was '0' vg->m_gdi_dc->ReleaseHDC(hdcMem); EndPaint(vg->m_hwnd, &ps); //end paint return 1; } ---8<----------------------- My apologies for the long post. Does anybody know what I'm not quite understanding regarding how you write to an offscreen buffer using GDI+ (or GDI for that matter)and then display this on screen? Thank you for reading.

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• SQL Server CTE referred in self joins slow

  - by Kharlos Dominguez

  Hello, I have written a table-valued UDF that starts by a CTE to return a subset of the rows from a large table. There are several joins in the CTE. A couple of inner and one left join to other tables, which don't contain a lot of rows. The CTE has a where clause that returns the rows within a date range, in order to return only the rows needed. I'm then referencing this CTE in 4 self left joins, in order to build subtotals using different criterias. The query is quite complex but here is a simplified pseudo-version of it WITH DataCTE as ( SELECT [columns] FROM table INNER JOIN table2 ON [...] INNER JOIN table3 ON [...] LEFT JOIN table3 ON [...] ) SELECT [aggregates_columns of each subset] FROM DataCTE Main LEFT JOIN DataCTE BananasSubset ON [...] AND Product = 'Bananas' AND Quality = 100 LEFT JOIN DataCTE DamagedBananasSubset ON [...] AND Product = 'Bananas' AND Quality < 20 LEFT JOIN DataCTE MangosSubset ON [...] GROUP BY [ I have the feeling that SQL Server gets confused and calls the CTE for each self join, which seems confirmed by looking at the execution plan, although I confess not being an expert at reading those. I would have assumed SQL Server to be smart enough to only perform the data retrieval from the CTE only once, rather than do it several times. I have tried the same approach but rather than using a CTE to get the subset of the data, I used the same select query as in the CTE, but made it output to a temp table instead. The version referring the CTE version takes 40 seconds. The version referring the temp table takes between 1 and 2 seconds. Why isn't SQL Server smart enough to keep the CTE results in memory? I like CTEs, especially in this case as my UDF is a table-valued one, so it allowed me to keep everything in a single statement. To use a temp table, I would need to write a multi-statement table valued UDF, which I find a slightly less elegant solution. Did some of you had this kind of performance issues with CTE, and if so, how did you get them sorted? Thanks, Kharlos

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• VBA Excel - Workbook_SheetChange

  - by user2947014

  Hopefully this question hasn't already been asked, I tried searching for an answer and couldn't find anything. This is probably a simple question, but I am writing my first macro in excel and am having a problem that I can't find out a solution to. I wrote a couple of macros that basically sum up columns dynamically (so that the number of rows can change and the formula moves down automatically) based on a value in another column of the same row, and I call those macros from the event Workbook_SheetChange. The problem I'm having is, I change a cell's value from my macro to display the result of the sum, and this then calls Workbook_SheetChange again, which I do not want. Right now it works, but I can trace it and see that Workbook_SheetChange is being called multiple times. This is preventing me from adding other cell changes to the macros, because then it results in an infinite loop. I want the macros to run every time a change is made to the sheet, but I don't see any way around allowing the macros to change a cell's value, so I don't know what to do. I will paste my code below, in case it is helpful. Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range) Dim Row As Long Dim Col As Long Row = Target.Row Col = Target.Column If Col <> 7 Then Range("G" & Row).Select Selection.Formula = "=IF(F" & Row & "=""Win"",E" & Row & ",IF(F" & Row & "=""Loss"",-D" & Row & ",0))" Target.Select End If Call SumRiskColumn End Sub Private Sub Workbook_SheetCalculate(ByVal Sh As Object) Call SumOutcomeColumn End Sub Sub SumOutcomeColumn() Dim N As Long N = Cells(Rows.Count, "A").End(xlUp).Row Cells(N + 1, "G").Formula = "=SUM(G2:G" & N & ")" End Sub Sub SumRiskColumn() Dim N As Long N = Cells(Rows.Count, "A").End(xlUp).Row Dim CurrTotalRisk As Long CurrTotalRisk = 0 For i = 2 To N If IsEmpty(ActiveSheet.Cells(i, 6)) And Not IsEmpty(ActiveSheet.Cells(i, 1)) And Not IsEmpty(ActiveSheet.Cells(i, 2)) And Not IsEmpty(ActiveSheet.Cells(i, 3)) Then CurrTotalRisk = CurrTotalRisk + ActiveSheet.Cells(i, 4).Value End If Next i Cells(N + 1, "D").Value = CurrTotalRisk End Sub Thank you for any help you can give me! I really appreciate it.

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• approximating log10[x^k0 + k1]

  - by Yale Zhang

  Greetings. I'm trying to approximate the function Log10[x^k0 + k1], where .21 < k0 < 21, 0 < k1 < ~2000, and x is integer < 2^14. k0 & k1 are constant. For practical purposes, you can assume k0 = 2.12, k1 = 2660. The desired accuracy is 5*10^-4 relative error. This function is virtually identical to Log[x], except near 0, where it differs a lot. I already have came up with a SIMD implementation that is ~1.15x faster than a simple lookup table, but would like to improve it if possible, which I think is very hard due to lack of efficient instructions. My SIMD implementation uses 16bit fixed point arithmetic to evaluate a 3rd degree polynomial (I use least squares fit). The polynomial uses different coefficients for different input ranges. There are 8 ranges, and range i spans (64)2^i to (64)2^(i + 1). The rational behind this is the derivatives of Log[x] drop rapidly with x, meaning a polynomial will fit it more accurately since polynomials are an exact fit for functions that have a derivative of 0 beyond a certain order. SIMD table lookups are done very efficiently with a single _mm_shuffle_epi8(). I use SSE's float to int conversion to get the exponent and significand used for the fixed point approximation. I also software pipelined the loop to get ~1.25x speedup, so further code optimizations are probably unlikely. What I'm asking is if there's a more efficient approximation at a higher level? For example: Can this function be decomposed into functions with a limited domain like log2((2^x) * significand) = x + log2(significand) hence eliminating the need to deal with different ranges (table lookups). The main problem I think is adding the k1 term kills all those nice log properties that we know and love, making it not possible. Or is it? Iterative method? don't think so because the Newton method for log[x] is already a complicated expression Exploiting locality of neighboring pixels? - if the range of the 8 inputs fall in the same approximation range, then I can look up a single coefficient, instead of looking up separate coefficients for each element. Thus, I can use this as a fast common case, and use a slower, general code path when it isn't. But for my data, the range needs to be ~2000 before this property hold 70% of the time, which doesn't seem to make this method competitive. Please, give me some opinion, especially if you're an applied mathematician, even if you say it can't be done. Thanks.

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• How do you create a MANIFEST.MF that's available when you're testing and running from a jar in produ

  - by warvair

  I've spent far too much time trying to figure this out. This should be the simplest thing and everyone who distributes Java applications in jars must have to deal with it. I just want to know the proper way to add versioning to my Java app so that I can access the version information when I'm testing, e.g. debugging in Eclipse and running from a jar. Here's what I have in my build.xml: <target name="jar" depends = "compile"> <property name="version.num" value="1.0.0"/> <buildnumber file="build.num"/> <tstamp> <format property="TODAY" pattern="yyyy-MM-dd HH:mm:ss" /> </tstamp> <manifest file="${build}/META-INF/MANIFEST.MF"> <attribute name="Built-By" value="${user.name}" /> <attribute name="Built-Date" value="${TODAY}" /> <attribute name="Implementation-Title" value="MyApp" /> <attribute name="Implementation-Vendor" value="MyCompany" /> <attribute name="Implementation-Version" value="${version.num}-b${build.number}"/> </manifest> <jar destfile="${build}/myapp.jar" basedir="${build}" excludes="*.jar" /> </target> This creates /META-INF/MANIFEST.MF and I can read the values when I'm debugging in Eclipse thusly: public MyClass() { try { InputStream stream = getClass().getResourceAsStream("/META-INF/MANIFEST.MF"); Manifest manifest = new Manifest(stream); Attributes attributes = manifest.getMainAttributes(); String implementationTitle = attributes.getValue("Implementation-Title"); String implementationVersion = attributes.getValue("Implementation-Version"); String builtDate = attributes.getValue("Built-Date"); String builtBy = attributes.getValue("Built-By"); } catch (IOException e) { logger.error("Couldn't read manifest."); } } But, when I create the jar file, it loads the manifest of another jar (presumably the first jar loaded by the application - in my case, activation.jar). Also, the following code doesn't work either although all the proper values are in the manifest file. Package thisPackage = getClass().getPackage(); String implementationVersion = thisPackage.getImplementationVersion(); Any ideas?

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• Slow MySQL query....only sometimes

  - by Shane N

  I have a query that's used in a reporting system of ours that sometimes runs quicker than a second, and other times takes 1 to 10 minutes to run. Here's the entry from the slow query log: # Query_time: 543 Lock_time: 0 Rows_sent: 0 Rows_examined: 124948974 use statsdb; SELECT count(distinct Visits.visitorid) as 'uniques' FROM Visits,Visitors WHERE Visits.visitorid=Visitors.visitorid and candidateid in (32) and visittime>=1275721200 and visittime<=1275807599 and (omit=0 or omit>=1275807599) AND Visitors.segmentid=9 AND Visits.visitorid NOT IN (SELECT Visits.visitorid FROM Visits,Visitors WHERE Visits.visitorid=Visitors.visitorid and candidateid in (32) and visittime<1275721200 and (omit=0 or omit>=1275807599) AND Visitors.segmentid=9); It's basically counting unique visitors, and it's doing that by counting the visitors for today and then substracting those that have been here before. If you know of a better way to do this, let me know. I just don't understand why sometimes it can be so quick, and other times takes so long - even with the same exact query under the same server load. Here's the EXPLAIN on this query. As you can see it's using the indexes I've set up: id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY Visits range visittime_visitorid,visitorid visittime_visitorid 4 NULL 82500 Using where; Using index 1 PRIMARY Visitors eq_ref PRIMARY,cand_visitor_omit PRIMARY 8 statsdb.Visits.visitorid 1 Using where 2 DEPENDENT SUBQUERY Visits ref visittime_visitorid,visitorid visitorid 8 func 1 Using where 2 DEPENDENT SUBQUERY Visitors eq_ref PRIMARY,cand_visitor_omit PRIMARY 8 statsdb.Visits.visitorid 1 Using where I tried to optimize the query a few weeks ago and came up with a variation that consistently took about 2 seconds, but in practice it ended up taking more time since 90% of the time the old query returned much quicker. Two seconds per query is too long because we are calling the query up to 50 times per page load, with different time periods. Could the quick behavior be due to the query being saved in the query cache? I tried running 'RESET QUERY CACHE' and 'FLUSH TABLES' between my benchmark tests and I was still getting quick results most of the time. Note: last night while running the query I got an error: Unable to save result set. My initial research shows that may be due to a corrupt table that needs repair. Could this be the reason for the behavior I'm seeing? In case you want server info: Accessing via PHP 4.4.4 MySQL 4.1.22 All tables are InnoDB We run optimize table on all tables weekly The sum of both the tables used in the query is 500 MB MySQL config: key_buffer = 350M max_allowed_packet = 16M thread_stack = 128K sort_buffer = 14M read_buffer = 1M bulk_insert_buffer_size = 400M set-variable = max_connections=150 query_cache_limit = 1048576 query_cache_size = 50777216 query_cache_type = 1 tmp_table_size = 203554432 table_cache = 120 thread_cache_size = 4 wait_timeout = 28800 skip-external-locking innodb_file_per_table innodb_buffer_pool_size = 3512M innodb_log_file_size=100M innodb_log_buffer_size=4M

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• Monitoring UDP socket in glib(mm) eats up CPU time

  - by Gyorgy Szekely

  Hi, I have a GTKmm Windows application (built with MinGW) that receives UDP packets (no sending). The socket is native winsock and I use glibmm IOChannel to connect it to the application main loop. The socket is read with recvfrom. My problem is: this setup eats 25% percent CPU time on a 3GHz workstation. Can somebody tell me why? The application is idle in this case, and if I remove the UDP code, CPU usage drops down to almost zero. As the application has to perform some CPU intensive tasks, I could image better ways to spend that 25% Here are some code excerpts: (sorry for the printf's ;) ) /* bind */ void UDPInterface::bindToPort(unsigned short port) { struct sockaddr_in target; WSADATA wsaData; target.sin_family = AF_INET; target.sin_port = htons(port); target.sin_addr.s_addr = 0; if ( WSAStartup ( 0x0202, &wsaData ) ) { printf("WSAStartup failed!\n"); exit(0); // :) WSACleanup(); } sock = socket( AF_INET, SOCK_DGRAM, 0 ); if (sock == INVALID_SOCKET) { printf("invalid socket!\n"); exit(0); } if (bind(sock,(struct sockaddr*) &target, sizeof(struct sockaddr_in) ) == SOCKET_ERROR) { printf("failed to bind to port!\n"); exit(0); } printf("[UDPInterface::bindToPort] listening on port %i\n", port); } /* read */ bool UDPInterface::UDPEvent(Glib::IOCondition io_condition) { recvfrom(sock, (char*)buf, BUF_SIZE*4, 0, NULL, NULL); /* process packet... */ } /* glibmm connect */ Glib::RefPtr channel = Glib::IOChannel::create_from_win32_socket(udp.sock); Glib::signal_io().connect( sigc::mem_fun(udp, &UDPInterface::UDPEvent), channel, Glib::IO_IN ); I've read here in some other question, and also in glib docs (g_io_channel_win32_new_socket()) that the socket is put into nonblocking mode, and it's "a side-effect of the implementation and unavoidable". Does this explain the CPU effect, it's not clear to me? Whether or not I use glib to access the socket or call recvfrom() directly doesn't seem to make much difference, since CPU is used up before any packet arrives and the read handler gets invoked. Also glibmm docs state that it's ok to call recvfrom() even if the socket is polled (Glib::IOChannel::create_from_win32_socket()) I've tried compiling the program with -pg and created a per function cpu usage report with gprof. This wasn't usefull because the time is not spent in my program, but in some external glib/glibmm dll.

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• Implementing Skip List in C++

  - by trikker

  [SOLVED] So I decided to try and create a sorted doubly linked skip list... I'm pretty sure I have a good grasp of how it works. When you insert x the program searches the base list for the appropriate place to put x (since it is sorted), (conceptually) flips a coin, and if the "coin" lands on a then that element is added to the list above it(or a new list is created with element in it), linked to the element below it, and the coin is flipped again, etc. If the "coin" lands on b at anytime then the insertion is over. You must also have a -infinite stored in every list as the starting point so that it isn't possible to insert a value that is less than the starting point (meaning that it could never be found.) To search for x, you start at the "top-left" (highest list lowest value) and "move right" to the next element. If the value is less than x than you continue to the next element, etc. until you have "gone too far" and the value is greater than x. In this case you go back to the last element and move down a level, continuing this chain until you either find x or x is never found. To delete x you simply search x and delete it every time it comes up in the lists. For now, I'm simply going to make a skip list that stores numbers. I don't think there is anything in the STL that can assist me, so I will need to create a class List that holds an integer value and has member functions, search, delete, and insert. The problem I'm having is dealing with links. I'm pretty sure I could create a class to handle the "horizontal" links with a pointer to the previous element and the element in front, but I'm not sure how to deal with the "vertical" links (point to corresponding element in other list?) If any of my logic is flawed please tell me, but my main questions are: How to deal with vertical links and whether my link idea is correct Now that I read my class List idea I'm thinking that a List should hold a vector of integers rather than a single integer. In fact I'm pretty positive, but would just like some validation. I'm assuming the coin flip would simply call int function where rand()%2 returns a value of 0 or 1 and if it's 0 then a the value "levels up" and if it's 0 then the insert is over. Is this incorrect? How to store a value similar to -infinite? Edit: I've started writing some code and am considering how to handle the List constructor....I'm guessing that on its construction, the "-infinite" value should be stored in the vectorname[0] element and I can just call insert on it after its creation to put the x in the appropriate place.

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• Few doubts regarding Bitmaps , Images & `using` blocks

  - by imageWorker

  I caught up in this problem. http://stackoverflow.com/questions/2559826/garbage-collector-not-doing-its-job-memory-consumption-1-5gb-outofmemory-exc I feel that there is something wrong in my understanding. Please clarify these things. Destructor & IDisposable.Dispose are two methods for freeing resources that are not not under the control of .NET. Which means, everything except memory. right? using blocks are just better way of calling IDisposable.Dispose() method of an object. This is the main code I'm referring to. class someclass { static someMethod(Bitmap img) { Bitmap bmp = new Bitmap(img); //statement1 // some code here and return } } here is class I'm using for testing: class someotherClass { public static voide Main() { foreach (string imagePath in imagePathsArray) { using (Bitmap img1 = new Bitmap(imagePath)) { someclass.someMethod(img1); // does some more processing on `img1` } } } } Is there any memory leak with statement1? Question1: If each image size is say 10MB. Then does this bmp object occupy atleast 10MB? What I mean is, will it make completely new copy of entire image? or just refer to it? Question2:should I or should I not put the statement1 in using block? My Argument: We should not. Because using is not for freeing memory but for freeing the resources (file handle in this case). If I use it in using block. It closes file handle here encapsulated by this bmp object. It means we are also closing filehandle for the caller's img1 object. Which is not correct? As of the memory leak. No there is no scope of memory leak here. Because reference bmp is destroyed when this method is returned. Which leaves memory it refered without any pointer. So, its garbage collected. Am I right? Edit: class someclass { static Bitmap someMethod(Bitmap img) { Bitmap bmp = new Bitmap(img); //can I use `using` block on this enclosing `return bmp`; ??? // do some processing on bmp here return bmp; } }

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• Asp.net MVC jquery-ajax dont render html

  - by Troublesum

  Hi, Im trying to use jqeury ajax with MVC i can get it to post back to the action i want and it returns the ViewData objects with updated Data but never renders the HTML. I have i View which contains some MVC User Controls and i want them to update on a timer. Here is my View Markup <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/PageWithSummaryViewAndTabs.Master" Inherits="System.Web.Mvc.ViewPage" %> <asp:Content ID="FullCaseTitle" ContentPlaceHolderID="TitleContent" runat="server"> </asp:Content> <asp:Content ID="FullCaseContent" ContentPlaceHolderID="MainContent" runat="server"> <script type="text/javascript"> window.setInterval(test, 5000); function test() { jQuery.get("/PatientCase/RefreshEPRF", function(response) { }); } </script> <div id="loadingDiv" style="display:none">Updating</div> <input id="refreshPatientCaseIndexButton" type="submit" visible="true" title="refresh" value="Refresh" /> <h2>Full Case</h2> <div id="EPRFContent"> <%Html.RenderPartial(@"~/Views/PatientCase/SectionEPRF.ascx"); %> <%Html.RenderPartial(@"~/Views/PatientCase/SectionDrugs.ascx"); %> </div> <div id="ImageContent"> <%Html.RenderPartial(@"~/Views/PatientCase/SectionImagery.ascx"); % On postback i call a Action Called RefreshEPRF which loads just the required user controls again <%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <%Html.RenderPartial(@"~/Views/PatientCase/SectionEPRF.ascx"); %> <%Html.RenderPartial(@"~/Views/PatientCase/SectionDrugs.ascx"); %> And finaly the marpup in the control <table id="detailstable"> <tr><td id="detailslablecolumn">Patient Name : </td><td> <% foreach (var item in (List<STS_Lite.Models.PatinetCase.EPRFItem>)ViewData["EPRF"]) { if (item.datumItemId == 46) { if (item.Stroke) { %> <img src="/PatientCaseIndex/InkImageData/GetInkImage/<%=ViewData["PatientCaseId"]%>/<%=ViewData["TemplateInstanceId"]%>/<%=item.TemplateItemId %>" /> <% } else {%> <%=item.Value.ToString()%> <%} break; } } %></td></tr><table> When i step through this code the ViewData in the user control has the new updated values but the page comes back with no new values. I have tried the jquery.get and ajax but with no luck. Any help would be great thanks

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• How would you implement this "WorkerChain" functionality in .NET?

  - by Dan Tao

  Sorry for the vague question title -- not sure how to encapsulate what I'm asking below succinctly. (If someone with editing privileges can think of a more descriptive title, feel free to change it.) The behavior I need is this. I am envisioning a worker class that accepts a single delegate task in its constructor (for simplicity, I would make it immutable -- no more tasks can be added after instantiation). I'll call this task T. The class should have a simple method, something like GetToWork, that will exhibit this behavior: If the worker is not currently running T, then it will start doing so right now. If the worker is currently running T, then once it is finished, it will start T again immediately. GetToWork can be called any number of times while the worker is running T; the simple rule is that, during any execution of T, if GetToWork was called at least once, T will run again upon completion (and then if GetToWork is called while T is running that time, it will repeat itself again, etc.). Now, this is pretty straightforward with a boolean switch. But this class needs to be thread-safe, by which I mean, steps 1 and 2 above need to comprise atomic operations (at least I think they do). There is an added layer of complexity. I have need of a "worker chain" class that will consist of many of these workers linked together. As soon as the first worker completes, it essentially calls GetToWork on the worker after it; meanwhile, if its own GetToWork has been called, it restarts itself as well. Logically calling GetToWork on the chain is essentially the same as calling GetToWork on the first worker in the chain (I would fully intend that the chain's workers not be publicly accessible). One way to imagine how this hypothetical "worker chain" would behave is by comparing it to a team in a relay race. Suppose there are four runners, W1 through W4, and let the chain be called C. If I call C.StartWork(), what should happen is this: If W1 is at his starting point (i.e., doing nothing), he will start running towards W2. If W1 is already running towards W2 (i.e., executing his task), then once he reaches W2, he will signal to W2 to get started, immediately return to his starting point and, since StartWork has been called, start running towards W2 again. When W1 reaches W2's starting point, he'll immediately return to his own starting point. If W2 is just sitting around, he'll start running immediately towards W3. If W2 is already off running towards W3, then W2 will simply go again once he's reached W3 and returned to his starting point. The above is probably a little convoluted and written out poorly. But hopefully you get the basic idea. Obviously, these workers will be running on their own threads. Also, I guess it's possible this functionality already exists somewhere? If that's the case, definitely let me know!

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• Reading column header and column values of a data table using LAMBDA(C#3.0)

  - by Newbie

  Consider the folowing where I am reading the data table values and writing to a text file using (StreamWriter sw = new StreamWriter(@"C:\testwrite.txt",true)) { DataPreparation().AsEnumerable().ToList().ForEach(i => { string col1 = i[0].ToString(); string col2 = i[1].ToString(); string col3 = i[2].ToString(); string col4 = i[3].ToString(); sw.WriteLine( col1 + "\t" + col2 + "\t" + col3 + "\t" + col4 + Environment.NewLine ); }); } The data preparation function is as under private static DataTable DataPreparation() { DataTable dt = new DataTable(); dt.Columns.Add("Col1", typeof(string)); dt.Columns.Add("Col2", typeof(int)); dt.Columns.Add("Col3", typeof(DateTime)); dt.Columns.Add("Col4", typeof(bool)); for (int i = 0; i < 10; i++) { dt.Rows.Add("String" + i.ToString(), i, DateTime.Now.Date, (i % 2 == 0) ? true : false); } return dt; } It is working fine. Now in the above described program, it is known to me the Number of columns and the column headers. How to achieve the same in case when the column headers and number of columns are not known at compile time using the lambda expression? I have already done that which is as under public static void WriteToTxt(string directory, string FileName, DataTable outData, string delimiter) { FileStream fs = null; StreamWriter streamWriter = null; using (fs = new FileStream(directory + "\\" + FileName + ".txt", FileMode.Append, FileAccess.Write)) { try { streamWriter = new StreamWriter(fs); streamWriter.BaseStream.Seek(0, SeekOrigin.End); streamWriter.WriteLine(); DataTableReader datatableReader = outData.CreateDataReader(); for (int header = 0; header < datatableReader.FieldCount; header++) { streamWriter.Write(outData.Columns[header].ToString() + delimiter); } streamWriter.WriteLine(); int row = 0; while (datatableReader.Read()) { for (int field = 0; field < datatableReader.FieldCount; field++) { streamWriter.Write(outData.Rows[row][field].ToString() + delimiter); } streamWriter.WriteLine(); row++; } } catch (Exception ex) { throw ex; } } } I am using C#3.0 and framework 3.5 Thanks in advance

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• Migrating from hand-written persistence layer to ORM

  - by Sergey Mikhanov

  Hi community, We are currently evaluating options for migrating from hand-written persistence layer to ORM. We have a bunch of legacy persistent objects (~200), that implement simple interface like this: interface JDBC { public long getId(); public void setId(long id); public void retrieve(); public void setDataSource(DataSource ds); } When retrieve() is called, object populates itself by issuing handwritten SQL queries to the connection provided using the ID it received in the setter (this usually is the only parameter to the query). It manages its statements, result sets, etc itself. Some of the objects have special flavors of retrive() method, like retrieveByName(), in this case a different SQL is issued. Queries could be quite complex, we often join several tables to populate the sets representing relations to other objects, sometimes join queries are issued on-demand in the specific getter (lazy loading). So basically, we have implemented most of the ORM's functionality manually. The reason for that was performance. We have very strong requirements for speed, and back in 2005 (when this code was written) performance tests has shown that none of mainstream ORMs were that fast as hand-written SQL. The problems we are facing now that make us think of ORM are: Most of the paths in this code are well-tested and are stable. However, some rarely-used code is prone to result set and connection leaks that are very hard to detect We are currently squeezing some additional performance by adding caching to our persistence layer and it's a huge pain to maintain the cached objects manually in this setup Support of this code when DB schema changes is a big problem. I am looking for an advice on what could be the best alternative for us. As far as I know, ORMs has advanced in last 5 years, so it might be that now there's one that offers an acceptable performance. As I see this issue, we need to address those points: Find some way to reuse at least some of the written SQL to express mappings Have the possibility to issue native SQL queries without the necessity to manually decompose their results (i.e. avoid manual rs.getInt(42) as they are very sensitive to schema changes) Add a non-intrusive caching layer Keep the performance figures. Is there any ORM framework you could recommend with regards to that?

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