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  • net c# lock statement in data access layer

    - by Pedro Rivera
    I saw a code where they have the data access layer like this: public class CustomerDA{ private static readonly object _sync = new object(); private static readonly CustomerDA _mutex = new CustomerDA(); private CustomerDA(){ } public CustomerDA GetInstance(){ lock(_sync){ return _mutex; } } public DataSet GetCustomers(){ //database SELECT //return a DataSet } public int UpdateCustomer(some parameters){ //update some user } } public class CustomerBO{ public DataSet GetCustomers(){ //some bussiness logic return CustomerDA.GetInstance().GetCustomers(); } } I was using it, but start thinking... "and what if had to build a facebook like application where there are hundreds of thousands of concurrent users? would I be blocking each user from doing his things until the previous user ends his database stuff? and for the Update method, is it useful to LOCK THREADS in the app when database engines already manage concurrency at database server level?" Then I started to think about moving the lock to the GetCustomers and UpdateCustomer methods, but think again: "is it useful at all?"

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  • Which C++ graphics library should I use?

    - by mspoerr
    Hello, I found the following graphics libraries, but I am not sure which one I should use. Maybe there are some more... Graphviz (http://www.graphviz.org/) Boost Graph Library (http://www.boost.org/doc/libs/1_42_0/libs/graph/doc/index.html) Lemon (http://lemon.cs.elte.hu/trac/lemon) igraph (http://igraph.sourceforge.net/introduction.html) What it should do: draw a undirected network map come as header only or static lib for Windows the output format should be user editable Graphviz is the only one I tried so far, but I found no static lib for it, I failed to build it by my own and the documentation could be better. Therefore I looked around and found these other three libs. I would be glad to get some recommendations which lib to choose. Thanks, /mspoerr

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  • Why do I get CA1811 when I call a private method from a public method in C++/CLI?

    - by brickner
    I've recently upgraded my project from Visual Studio 2008 to Visual Studio 2010. By enabling Code Analysis and building on Release, I'm getting warning CA1811: Avoid uncalled private code. I've managed to reduce the code to this: .h file: public ref class Foo { public: virtual System::String^ ToString() override; private: static System::String^ Bar(); }; .cpp file: String^ Foo::ToString() { return Bar(); } String^ Foo::Bar() { return "abc"; } The warning I get: CA1811 : Microsoft.Performance : 'Foo::Bar(void)' appears to have no upstream public or protected callers. It doesn't matter if Bar() is static or not. I've tried to reproduce it in C# but I can't. I can only reproduce it in C++/CLI. Why do I get this warning? Is this a Visual Studio 2010 bug?

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  • How do i return a StringWriter When I cant Clone it?

    - by acidzombie24
    My code looks like the below. Obviously i cant write 'ok' because the object has been disposed. I cant do return sw.Clone() bc clone doesnt exist. If i dont use a using then at any point between = new and return (like iterating and writing to the object as my example doesnt do) can have an exception and thus not disposing the object. Am i to define sw outside of a try block and check if its null then dispose in a catch block? That seems like a bit of excessive work. Is there a better way? is that the only way? static void func1() { using (var sw = func2()) { sw.WriteLine("Ok"); } } static StringWriter func2() { using (var sw = new StringWriter()) { return sw; } }

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  • Convert Stream to IEnumerable. If possible when "keeping laziness"

    - by Binary255
    Hi, I recieve a Stream and need to pass in a IEnumerable to another method. public static void streamPairSwitchCipher(Stream someStream) { ... someStreamAsIEnumerable = ... IEnumerable returned = anotherMethodWhichWantsAnIEnumerable(someStreamAsIEnumerable); ... } One way is to read the entire Stream, convert it to an Array of bytes and pass it in, as Array implements IEnumerable. But it would be much nicer if I could pass in it in such a way that I don't have to read the entire Stream before passing it in. public static IEnumerable<T> anotherMethodWhichWantsAnIEnumerable<T>(IEnumerable<T> p) { ... // Something uninteresting }

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  • HTML5: Can't drag on-the-fly created <div> tag even though draggable='true' Do I need to "BLESS"

    - by Pete Alvin
    After creating a div on the fly with this markup: $('.circuit').prepend("<div class='component' draggable='true'>TRANSISTOR</div>"); It is NOT draggable itself :( Is jQuery prepend() the correct way to create "live" tags in the DOM? Do I need to somehow bless it a different way to make draggable=true really work? How to I wire it up so that on-the-fly divs can be draggable? AFTER NOTE: I added a static div and that is draggable. INTERESTING: I view both the static and dynamic using FireFox F12 Firebug and they are identical. But one is draggable and one is not!!!

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  • Facebook writing on a wall problem - retrieves only null value.

    - by Viral
    hi all friends, I am making a game application in that I want to pass my score on wall of face book. I've completed all the things (the log in and message passing part) but when I passes the score via global variable, I am getting only null as a value and not the score that I want. Is there any way to pass data or string to Face book and write on a wall? My code is (void)viewDidLoad { static NSString* kApiKey = @"be60415be308e2b44c0ac1db83fe486b"; static NSString* kApiSecret = @"4f880c7e100321f808c41b1d3c813dfa"; _session = [[FBSession sessionForApplication:kApiKey secret:kApiSecret delegate:self] retain]; score = [NSString stringWithFormat:@"%@",appDelegate.myTextView]; [_session resume]; [super viewDidLoad]; } whre score is NSString and myTextView is NSString in other viewcontrollerfile, And appDelegate is global variable. Any help?? thanks in advance.

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  • Chaning coding style due to Android GC performance, how far is too far?

    - by Benju
    I keep hearing that Android applications should try to limit the number of objects created in order to reduce the workload on the garbage collector. It makes sense that you may not want to created massive numbers of objects to track on a limited memory footprint, for example on a traditional server application created 100,000 objects within a few seconds would not be unheard of. The problem is how far should I take this? I've seen tons of examples of Android applications relying on static state in order supposedly "speed things up". Does increasing the number of instances that need to be garbage collected from dozens to hundreds really make that big of a difference? I can imagine changing my coding style to now created hundreds of thousands of objects like you might have on a full-blown Java-EE server but relying on a bunch of static state to (supposedly) reduce the number of objects to be garbage collected seems odd. How much is it really necessary to change your coding style in order to create performance Android apps?

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  • Override bits of a CSS class while inline?

    - by larryq
    I have an html img that is being styled by a CSS class. I would like to override the width and height values used in that class under some circumstances. I'm building this img tag using something called a TagBuilder class, provided by Microsoft for the .Net system, which allows developers to assign attributes to an html element. In this case a CSS class has been assigned to the img tag, and I can assign width and height attributes individually, but they're not taking precedence over the values set in the CSS class. My tag looks like this currently: <img alt="my link" class="static" height="240" id="StaticImage" src="http://imageserver.com/myImage.jpg" width="240"> The static CSS class has width and height values of 300 each, and as you can see I'm trying to override them with 240. It's not working in this instance but can I do it without a second CSS class?

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  • Why is javac 1.5 running so slowly compared with the Eclipse compiler?

    - by Simon Nickerson
    I have a Java Maven project with about 800 source files (some generated by javacc/JTB) which is taking a good 25 minutes to compile with javac. When I changed my pom.xml over to use the Eclipse compiler, it takes about 30 seconds to compile. Any suggestions as to why javac (1.5) is running so slowly? (I don't want to switch over to the Eclipse compiler permanently, as the plugin for Maven seems more than a little buggy.) I have a test case which easily reproduces the problem. The following code generates a number of source files in the default package. If you try to compile ImplementingClass.java with javac, it will seem to pause for an inordinately long time. import java.io.File; import java.io.FileNotFoundException; import java.io.PrintStream; public class CodeGenerator { private final static String PATH = System.getProperty("java.io.tmpdir"); private final static int NUM_TYPES = 1000; public static void main(String[] args) throws FileNotFoundException { PrintStream interfacePs = new PrintStream(PATH + File.separator + "Interface.java"); PrintStream abstractClassPs = new PrintStream(PATH + File.separator + "AbstractClass.java"); PrintStream implementingClassPs = new PrintStream(PATH + File.separator + "ImplementingClass.java"); interfacePs.println("public interface Interface<T> {"); abstractClassPs.println("public abstract class AbstractClass<T> implements Interface<T> {"); implementingClassPs.println("public class ImplementingClass extends AbstractClass<Object> {"); for (int i=0; i<NUM_TYPES; i++) { String nodeName = "Node" + i; PrintStream nodePs = new PrintStream(PATH + File.separator + nodeName + ".java"); nodePs.printf("public class %s { }\n", nodeName); nodePs.close(); interfacePs.printf("void visit(%s node, T obj);%n", nodeName); abstractClassPs.printf("public void visit(%s node, T obj) { System.out.println(obj.toString()); }%n", nodeName); } interfacePs.println("}"); abstractClassPs.println("}"); implementingClassPs.println("}"); interfacePs.close(); abstractClassPs.close(); implementingClassPs.close(); } }

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  • How To Get Type Info Without Using Generics?

    - by DaveDev
    Hi Guys I have an object obj that is passed into a helper method. public static MyTagGenerateTag<T>(this HtmlHelper htmlHelper, T obj /*, ... */) { Type t = typeof(T); foreach (PropertyInfo prop in t.GetProperties()) { object propValue = prop.GetValue(obj, null); string stringValue = propValue.ToString(); dictionary.Add(prop.Name, stringValue); } // implement GenerateTag } I've been told this is not a correct use of generics. Can somebody tell me if I can achieve the same result without specifying a generic type? If so, how? I would probably change the signature so it'd be like: public static MyTag GenerateTag(this HtmlHelper htmlHelper, object obj /*, ... */) { Type t = typeof(obj); // implement GenerateTag } but Type t = typeof(obj); is impossible. Any suggestions? Thanks Dave

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  • A simple Python extension in C

    - by celil
    I am trying to create a simple python extension module. I compiled the following code into a transit.so dynamic module #include <python2.6/Python.h> static PyObject* _print(PyObject* self, PyObject* args) { return Py_BuildValue("i", 10); } static PyMethodDef TransitMethods[] = { {"print", _print, METH_VARARGS, ""}, {NULL, NULL, 0, NULL} }; PyMODINIT_FUNC inittransit(void) { Py_InitModule("transit", TransitMethods); } However, trying to call this from python import transit transit.print() I obtain an error message File "test.py", line 2 transit.print() ^ SyntaxError: invalid syntax What's wrong with my code?

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  • JProgressBar.stringPainted(true); is not working

    - by Mirza Ghalib
    This is a part of my java code, in this code I have written that when I click the button the value of JProgressBar should becomes 0 and stringPainted(); becomes true, but "string painted" is not visible when I click the button, please help. import java.awt.Color; import java.awt.Dimension; import java.awt.FlowLayout; import java.awt.Graphics; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JProgressBar; public class R implements ActionListener { static int y; CustomProgressBar b = new CustomProgressBar(); public static void main(String arg[]) throws Exception { new R(); } public R() throws Exception { JFrame f = new JFrame(); JButton btn = new JButton("Click"); f.setExtendedState(JFrame.MAXIMIZED_BOTH); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.setUndecorated(true); f.setLayout(new FlowLayout()); btn.addActionListener(this); f.add(b); f.add(btn); f.setVisible(true); } class CustomProgressBar extends JProgressBar{ private static final long serialVersionUID = 1L; private boolean isStringToBePainted = false; public CustomProgressBar() { super(JProgressBar.VERTICAL,0,100); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); if(isStringToBePainted ) { Dimension size = CustomProgressBar.this.getSize(); if( CustomProgressBar.this.getPercentComplete()<0.9 ) R.y = (int)( size.height - size.height * CustomProgressBar.this.getPercentComplete() ); String text = getString(); g.setColor(Color.BLACK ); g.drawString(text, 0, R.y); } } @Override public void setStringPainted(boolean b) { isStringToBePainted=b; } } @Override public void actionPerformed(ActionEvent e) { b.setValue(0); b.setStringPainted(true); } }

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  • Problem with virtual mouse click

    - by Alex
    Hi. I have a program that simulates mouse click. Code is something like this: [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)] public static extern void mouse_event(long dwFlags, long dx, long dy, long cButtons, long dwExtraInfo); private const int MOUSEEVENTF_LEFTDOWN = 0x02; private const int MOUSEEVENTF_LEFTUP = 0x04; public static void DoMouseClick(int x, int y) { Cursor.Position = new Point(x, y); mouse_event(MOUSEEVENTF_LEFTDOWN | MOUSEEVENTF_LEFTUP, x, y, 0, 0); } This code works perfectly. For example I call this function every 30 minutes. But if I press WINKEY+L (Windows is locked) only cursor is moved but not press occurs. Any ideas?

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  • How should Application.Run() be called for the main presenter a MVP WinForms app?

    - by Mr Roys
    I'm learning to apply MVP to a simple WinForms app (only one form) in C# and encountered an issue while creating the main presenter in static void Main(). Is it a good idea to expose a View from the Presenter in order to supply it as a parameter to Application.Run()? Currently, I've implemented an approach which allows me to not expose the View as a property of Presenter: static void Main() { IView view = new View(); Model model = new Model(); Presenter presenter = new Presenter(view, model); presenter.Start(); Application.Run(); } The Start and Stop methods in Presenter: public void Start() { view.Start(); } public void Stop() { view.Stop(); } The Start and Stop methods in View (a Windows Form): public void Start() { this.Show(); } public void Stop() { // only way to close a message loop called // via Application.Run(); without a Form parameter Application.Exit(); } The Application.Exit() call seems like an inelegant way to close the Form (and the application). The other alternative would be to expose the View as a public property of the Presenter in order to call Application.Run() with a Form parameter. static void Main() { IView view = new View(); Model model = new Model(); Presenter presenter = new Presenter(view, model); Application.Run(presenter.View); } The Start and Stop methods in Presenter remain the same. An additional property is added to return the View as a Form: public void Start() { view.Start(); } public void Stop() { view.Stop(); } // New property to return view as a Form for Application.Run(Form form); public System.Windows.Form View { get { return view as Form(); } } The Start and Stop methods in View (a Windows Form) would then be written as below: public void Start() { this.Show(); } public void Stop() { this.Close(); } Could anyone suggest which is the better approach and why? Or there even better ways to resolve this issue?

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  • Inheritance domain classes in Grails

    - by Tomáš
    Hi gurus how can I get Collection of specific Class? I use inheriance: On Planet live Human. Humans are dividing to Men and Women. class Planet{ String name static hasMany = [ humans : Human ] } class Human{ String name static belongsTo = [Planet] } class Man extends Human{ int countOfCar } class Woman extends Human{ int coutOfChildren } now a neet to get only Collection of Man or Collection of Woman: get all humans on planet is simple all = Planet.get(1).humans but what can I get only woman or men? womenLivedOnMars = Planet.get(1).getOnlyWoman menLivedOnJupiter = Planet.get(2).getOnlyMan Thanks for your help Tom

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  • Data Access Layer in an ASP.NET website

    - by user3519124
    :) i have a DAL class file in my project, that my teacher sent me and explained to me but i did not really understand it. It has number of functions, and I understand only few of them, like with connecting to the database or creating a command object but there are 2 that I dont understand: public static DataTable GetTable(string str) { OleDbConnection con = DAL.GetConnection(); OleDbCommand cmd = DAL.GetCommand(con, str); DataTable dt = new DataTable(); OleDbDataAdapter adp = new OleDbDataAdapter(); adp.SelectCommand = cmd; adp.Fill(dt); return dt; } public static int ExecuteNonQuery(string str) { int num = -1; OleDbConnection con = DAL.GetConnection(); con.Open(); if (con.State == ConnectionState.Open) { OleDbCommand cmd = DAL.GetCommand(con, str); num = cmd.ExecuteNonQuery(); con.Close(); } return num; } thank you :)

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  • global std::unordered_map com server init problems

    - by PrettyFlower
    I want to have a static global std::unordered_map in the cpp of my entry point for my COM server. relevant header code: typedef unordered_map<HWND,IMyInterface*> MyMapType; relevant body: static MyMapType MyMap; void MyFunction(HWND hWnd, IMyInterface* pObj){ MyMap[HWND] = pObj; } HINSTANCE g_hInstModule = NULL; BOOL WINAPI DllMain ( __in HINSTANCE hInstDLL, __in DWORD fdwReason, __in LPVOID lpvReserved ) { if( fdwReason == DLL_PROCESS_ATTACH ) { g_hInstModule = hInstDLL; return true; } else if( fdwReason == DLL_PROCESS_DETACH ) { return true; } return false; } MyCoClass::MyCoClass() { DRM_Refcount = 1; } HRESULT STDMETHODCALLTYPE MyCoClass::InitMyCoClass() { CoInitializeEx(NULL, COINIT_APARTMENTTHREADED); //replace with make window code MyFunction(hWnd,ISomeInterface); return S_OK; } The only way I can get this to work is be making a map_type pointer and creating an instance of map_type on the heap and pointing at it with the global pointer. :/ WHY?

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  • Can JNI handle any dll files (Windows)?

    - by henry
    I am new to JNI. And have a few questions : Can JNI handle every type dll exists in windows? I wanted to link a library but it gives me error. Is it possible JNI and the dll are not compatible? Excerpt from VB .NET (It works) Private Declare Function ConnectReader Lib "rfidhid.dll" () As Integer Private Declare Function DisconnectReader Lib "rfidhid.dll" () As Integer Private Declare Function SetAntenna Lib "rfidhid.dll" (ByVal mode As Integer) As Integer Full Code From Java public class MainForm { /** * @param args */ public native int ConnectReader(); public static void main(String[] args) { // TODO Auto-generated method stub MainForm mf = new MainForm(); System.out.println(mf.ConnectReader()); } static { System.loadLibrary("rfidhid"); } } Error code shown Exception in thread "main" java.lang.UnsatisfiedLinkError: MainForm.ConnectReader()I at MainForm.ConnectReader(Native Method) at MainForm.main(MainForm.java:13) Can anyone point to me where I might do wrong

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  • Is there a standard .NET exception to throw when a class doesn't implement a required attribute?

    - by a typing monkey
    Suppose I want to throw a new exception when invoking a generic method with a type that doesn't have a required attribute. Is there a .NET exception that's appropriate for this situation, or, more likely, one that would be a suitable ancestor for a custom exception? For example: public static class ClassA { public static T DoSomething<T>(string p) { Type returnType = typeof(T); object[] typeAttributes = returnType.GetCustomAttributes(typeof(SerializableAttribute), true); if ((typeAttributes == null) || (typeAttributes.Length == 0)) { // Is there an exception type in the framework that I should use/inherit from here? throw new Exception("This class doesn't support blah blah blah"); // Maybe ArgumentException? That doesn't seem to fit right. } } } Thanks.

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  • C# simpler run time generics

    - by Hellfrost
    Is there a way to invoke a generic function with a type known only at run time? I'm trying to do something like: static void bar() { object b = 6; string c = foo<typeof(b)>(); } static string foo<T>() { return typeof (T).Name; } Basically I want to decide on the type parameter only at run time, but the function I'm calling depends on the type parameter. Also I know this can be done with reflections... but it's not the nicest solution to the problem... I'm sort of looking for dynamic features in C#...

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  • Using Apache Velocity with StringBuilders/CharSequences

    - by mindas
    We are using Apache Velocity for dynamic templates. At the moment Velocity has following methods for evaluation/replacing: public static boolean evaluate(Context context, Writer writer, String logTag, Reader reader) public static boolean evaluate(Context context, Writer out, String logTag, String instring) We use these methods by providing StringWriter to write evaluation results. Our incoming data is coming in StringBuilder format so we use StringBuilder.toString and feed it as instring. The problem is that our templates are fairly large (can be megabytes, tens of Ms on rare cases), replacements occur very frequently and each replacement operation triples the amount of required memory (incoming data + StringBuilder.toString() which creates a new copy + outgoing data). I was wondering if there is a way to improve this. E.g. if I could find a way to provide a Reader and Writer on top of same StringBuilder instance that only uses extra memory for in/out differences, would that be a good approach? Has anybody done anything similar and could share any source for such a class? Or maybe there any better solutions to given problem?

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  • Why would this line throw exception for type initializer failed?

    - by Jaggu
    I had a class: public class Constant { public static string ConnString = ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString; } which would throw exception on LIVE: Type initialize failed for Constant ctor If I change the class to: public class Constant { public static string ConnString { get { return ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString; } } } it works. I wasted 2 hours behind this but I still don't know why would this happen. Any ideas? Note: The 1st class used to work on DEV environment but not on LIVE. The 2nd class works on DEV and also on Production. I am using VS2010 on production and Asp.Net 4.0 Website project. I am totally amazed by this inconsistency to say the least! Edit: This class was in App_Code folder.

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  • Running Send_SMS method from BroadcastReceiver

    - by burmat
    My application is an auto-reply application for text messages. I have a BroadcastReceiver for when a message arrives, and I need it to run a public method (Send_SMS). SMS_Sender.sendSMS(phoneNumber, messageText); does not work however, and eclipse wants to change my method to static. This would not be an issue if I did not have more receivers that catch when the message is sent/delivered/etc in this class. These receivers are then errors for being contained in a static method. So my question is, how do I run this method from a broadcast receiver so I can send the auto reply whenever it is triggered with a received message? -Thank you in advance, Nate

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  • visual studio 2008 linker error

    - by ravi
    In visual studio 2008, I have created a static dll called test_static.dll. I am trying to call this from one application. I have included this dll in source files folder and the header file related to it in headers folder. When i am running the application I am getting following liking error. Please give me a solution. error LNK2019: unresolved external symbol "struct morph_output * __cdecl morpho_data(struct morph_input *)" (?morpho_data@@YAPAUmorph_output@@PAUmorph_input@@@Z) referenced in function _wmain 1D:\test_app\Debug\test_app.exe : fatal error LNK1120: 1 unresolved externals 1Build log was saved at "file://d:\test_app\test_app\Debug\BuildLog.htm" Here test_app is application that is using static dll. and morpho_data is the dll function which is taking input as structure and returning another structure.

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