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  • Annotations: methods vs variables

    - by Zenzen
    I was always sure (don't know why) that it's better to add annotations to variables, but while browsing the Hibernate doc http://docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity-hibspec-collection I noticed they tend to annotate the methods. So should I put my annotations before methods, like this: @Entity public class Flight implements Serializable { private long id; @Id @GeneratedValue public long getId() { return id; } public void setId(long id) { this.id = id; } } Or is it better to do it like this: @Entity public class Flight implements Serializable { @Id @GeneratedValue private long id; public long getId() { return id; } public void setId(long id) { this.id = id; } } Or maybe there's no difference?

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  • C++ and C#, "Casting" Functions to Delegates, What's the scoop?

    - by Jacob G
    In C# 2.0, I can do the following: public class MyClass { delegate void MyDelegate(int myParam); public MyClass(OtherObject obj) { //THIS IS THE IMPORTANT PART obj.SomeCollection.Add((MyDelegate)MyFunction); } private void MyFunction(int myParam); { //... } } Trying to implement the same thing in C++, it appears I have to do: MyDelegate del = gcnew MyDelegate(this, MyFunction); obj-SomeCollection-Add(del); Obviously I can create a new instance of the delegate in C# as well instead of what's going on up there. Is there some kind of magic going on in the C# world that doesn't exist in C++ that allows that cast to work? Some kind of magic anonymous delegate? Thanks.

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  • What is the explanation of this results in Java ?

    - by M.H
    I have the following code : public class Main { private int i = j; //1 private int j = 10; public static void main(String[] args) { System.out.println((new Main()).i); } } and there is a compiler error in line 1 because an illegal forward reference. But when I am trying the following code : public class Main { int i = getJ(); //1 int getJ(){ return j; } int j=10; public static void main(String[] args) { System.out.println(new Main().i); } } it works fine and the result is 0.Why there is no illegal forward reference in line 1 here?.The two codes look similar to me.

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  • wpf how to bind a listbox to a list (two ways) - c#

    - by user429400
    Hi, I want to create a 2 way bind between a listbox and a .NET list. In my GUI, I have a listbox, a textbox and add and remove buttons. The listbox displays cars, and my goal is to create a 2way bind between the .Net car list and the listbox: when the user enters a car into the textbox, it gets updated only in the .Net list, and the listbox is updated automatically. When the user press the GUI "remove" button, a car gets removed from the GUI and the .Net list is updated automatically. I've started to write the xaml code, but figured that I don't actually know how to do the binding on both sides (c# and xaml): <Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:c="clr-namespace:WpfApplication1" Title="Window1" Height="300" Width="369" Loaded="Window_Loaded"> <Window.Resources> <ObjectDataProvider x:Key="carsData" ObjectType="{x:Type c:Window1}" /> </Window.Resources> <Grid Width="332"> <ListBox Margin="10,62,0,100" Name="myListBox" HorizontalAlignment="Left" Width="120" ItemsSource="{Binding Source={StaticResource CarsData}}"/> <Button Height="23" Margin="66,0,0,65" Name="addBtn" VerticalAlignment="Bottom" Click="addBtn_Click" HorizontalAlignment="Left" Width="64">add</Button> <TextBox Margin="10,0,0,64.48" Name="myTextBox" Height="23" VerticalAlignment="Bottom" HorizontalAlignment="Left" Width="47" /> <Button Height="23" Margin="66,0,0,33" Name="removeButton" VerticalAlignment="Bottom" HorizontalAlignment="Left" Width="64" Click="removeButton_Click">Remove</Button> </Grid> </Window> There is my c# code: namespace WpfApplication1 { public partial class Window1 : Window { MyModel listMgr; ObservableCollection carList; public Window1() { InitializeComponent(); listMgr = new MyModel(); } private void addBtn_Click(object sender, RoutedEventArgs e) { listMgr.add(new Car(0, myTextBox.Text, 2011)); } private void removeButton_Click(object sender, RoutedEventArgs e) { //myListBox.Items.RemoveAt(0); } private void Window_Loaded(object sender, RoutedEventArgs e) { carList = listMgr.getList(); myListBox.DataContext = carList; //secondListBox.DataContext = carList; } } } Thanks, Li

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  • Action T synchronous and asynchronous

    - by raffaeu
    Hi everybody I have a contextmenustrip control that allows you to execute an action is two different flawours. Sync and Async. I am trying to covert everything using Generics so I did this: public class BaseContextMenu<T> : IContextMenu { private T executor ... public void Exec(Action<T> action){ action.Invoke(this.executor); } public void ExecAsync(Action<T> asyncAction){ ... } How I can write the async method in order to execute the generic action and 'do something' with the menu in the meanwhile? I saw that the signature of BeginInvoke is something like: asyncAction.BeginInvoke(thi.executor, IAsyncCallback, object);

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  • c++ when to put method out side the class

    - by user63898
    i saw that some times in c++ applications using only namespace declarations with header and source file like this : #ifndef _UT_ #define _UT_ #include <string> #include <windows.h> namespace UT { void setRootPath(char* program_path, char* file_path); char * ConvertStringToCharP(std::string str); }; #endif //and then in UT.cpp #include "UT.h" namespace UT { char * ConvertStringToCharP(std::string str) { char * writable = new char[str.size() + 1]; std::copy(str.begin(), str.end(), writable); writable[str.size()] = '\0'; return writable; } void setRootPath(char* program_path, char* file_path) { //... } } is it better then defining classic class with static methods? or just simple class ? dose this method has something better for the compiler linker ? the methods in this namespace are called allot of times .

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  • Android. Playing multiple sounds using SoundManager

    - by Jerry
    Shown are a few lines of code. If I play a single sound, it runs fine. Adding a second sound causes it to crash. Any advice is appreciated. private SoundManager mSoundManager; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.sos); mSoundManager = new SoundManager(); mSoundManager.initSounds(getBaseContext()); mSoundManager.addSound(1,R.raw.dit); mSoundManager.addSound(1,R.raw.dah); Button SoundButton = (Button)findViewById(R.id.SoundButton); SoundButton.setOnClickListener(new OnClickListener() { public void onClick(View v) { mSoundManager.playSound(1); mSoundManager.playSound(2); } }); }

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  • Calling managed code from unmanaged win32 assembly dll - crash

    - by JustGreg
    I'm developing a serial port dll in win32 assembly (MASM32). It has its own thread checking multiple events and at a specified buffer treshold it'd notify the managed main application by calling a callback function. It just a call with no arguments/return value. At startup the main application stores the callback function's address by calling a function in the dll: pCallBackFunction dd 0 SetCallBackPointer proc pcb:DWORD mov eax, pcb mov pCallBackFunction, eax call DWORD ptr pCallBackFunction ; verify it immediately ret SetCallBackPointer endp The upper function immediately calls back the managed application callback routine for verification purposes. It is working fine. However, when I place the call instruction to other functions in the dll it crashes the application. It doesn't matter if the call is in a simple function or in the threadproc of the dll. For example: OpenPort proc pn:byte,br:dword, inputbuffersize: dword, outputbuffersize:dword, tresholdsize: dword LOCAL dcb: DCB LOCAL SerialTimeOuts: COMMTIMEOUTS call DWORD ptr pCallBackFunction xor eax, eax mov al, pn mov [com_port+3],al etc. etc. will crash at call DWORD ptr pCallBackFunction always. Since I call SetCallBackPointer first to store a valid address in pCallBackFunction, it should have a valid address. My managed app is written in C# and the relevant part is: public partial class Form1 : Form { public delegate void CallBackDelegate(); public static CallBackDelegate mydelegate; [DllImport("serialport.dll")] private static extern void SetCallBackPointer(CallBackDelegate Delegate); [DllImport("serialport.dll")] public static extern int OpenPort(byte com, uint br, uint inbufsize, uint outbufsize, uint treshsize); public Form1() { InitializeComponent(); mydelegate =new CallBackDelegate(CallbackFunction); SetCallBackPointer(mydelegate); unsafe { int sysstat; int hResult; hResult = OpenPort(Convert.ToByte('5'), 9600, 306, 4, 4); } } public static void CallbackFunction() { MessageBox.Show( "CallBack Function Called by Windows DLL"); } The VS debugger reported that the dll had tried to read/write from/to a protected memory address. But when calling SetCallBackPointer there is no such problem. What am I doing wrong here? Any tips would be great!

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  • Why is 'virtual' optional for overridden methods in derived classes?

    - by squelart
    When a method is declared as virtual in a class, its overrides in derived classes are automatically considered virtual as well, and the C++ language makes this keyword virtual optional in this case: class Base { virtual void f(); }; class Derived : public Base { void f(); // 'virtual' is optional but implied. }; My question is: What is the rationale for making virtual optional? I know that it is not absolutely necessary for the compiler to be told that, but I would think that developers would benefit if such a constraint was enforced by the compiler. E.g., sometimes when I read others' code I wonder if a method is virtual and I have to track down its superclasses to determine that. And some coding standards (Google) make it a 'must' to put the virtual keyword in all subclasses.

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  • Logical value of an assignment in C

    - by Andy Shulman
    while (curr_data[1] != (unsigned int)NULL && ((curr_ptr = (void*)curr_data[1]) || 1)) Two part question. What will (curr_ptr = (void*)curr_data[1]) evaluate to, logically. TRUE? Also, I know its rather hack-ish, but is the while statement legal C? I would have to go through great contortions to put the assignment elsewhere in the code, so I'd be really nice if I could leave it there, but if it's so egregious that it makes everyone's eyeballs burst into flames, I'll change it.

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  • C++: incorrect swapping of nodes in linked list

    - by Dragon
    I have 2 simple structures: struct Address { char city[255]; }; typedef Address* AddressPtr; struct Person { char fullName[255]; Address* address; Person* next; }; typedef Person* PersonPtr; The Person structure forms the Linked list where new elements are added to the beginning of the list. What I want to do is to sort them by fullName. At first I tried to swap links, but I lost the beginning of the list and as a result my list was sorted partially. Then I decided to sort list by swapping the values of nodes. But I get strange results. For a list with names: Test3, Test2, Test1, I get Test3, Test3, Test3. Here is my sorting code: void sortByName(PersonPtr& head) { TaskPtr currentNode, nextNode; for(currentNode = head; currentNode->next != NULL; currentNode = currentNode->next) { for(nextNode = currentNode->next; nextNode != NULL; nextNode = nextNode->next) { if(strcmp(currentNode->fullName, nextNode->fullName) > 0) { swapNodes(currentNode, nextNode); } } } } void swapNodes(PersonPtr& node1, PersonPtr& node2) { PersonPtr temp_node = node2; strcpy(node2->fullName, node1->fullName); strcpy(node1->fullName, temp_node->fullName); strcpy(node2->address->city, node1->address->city); strcpy(node1->address->city, temp_node->address->city); } After the sorting completion, nodes values are a little bit strange. UPDATED This is how I swapped links void swapNodes(PersonPtr& node1, PersonPtr& node2) { PersonPtr temp_person; AddressPtr temp_address; temp_person = node2; node2 = node1; node1 = temp_person; temp_address = node2->address; node2->address = node1->address; node1->address = temp_address; }

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  • Can I compose a WCF callback contract out of multiple interfaces?

    - by mafutrct
    Followup question to http://stackoverflow.com/questions/2502930/how-can-i-compose-a-wcf-contract-out-of-multiple-interfaces. I tried to merge multiple callback interfaces in a single interface. This yields an InvalidOperationException claiming that the final interface contains no operations. Technically, this is true, however, the inherited interfaces do contain operations. How can I fix this? Or is this a limitation of WCF? Edit: interface A { [OperationContract]void X(); } interface B { [OperationContract]void Y(); } interface C: A, B {} // this is the public callback contract

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  • Is it possible to write a Java printf statement that prints the statement itself?

    - by polygenelubricants
    Is it possible to have a Java printf statement, whose output is the statement itself? Some snippet to illustrate: // attempt #1 public class Main { public static void main(String[] args) { System.out.printf("something"); } } This prints something. So the output of attempt #1 is not quite exactly the printf statement in attempt #1. We can try something like this: // attempt #2 public class Main { public static void main(String[] args) { System.out.printf("System.out.printf(\"something\");"); } } And now the output is System.out.printf("something"); So now the output of attempt #2 matches the statement in output #1, but we're back to the problem we had before, since we need the output of attempt #2 to match the statement in attempt #2. So is it possible to write a one-line printf statement that prints itself?

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  • Store Observer not being called always

    - by Nixarn
    Has anyone else here experienced problems with their Store Observer class not being called always when the user for instance cancels a request (or purchases something) We just had our update that brought in app purchases go live last night, and before that we had obviously tested everything tons of times against the Sandbox and everything was working fine. Now however, when the update went live in a real environment we keep getting issues with the store. For instance, in a freshly booted iPhone / iPod, the first time you run the app, if you then try to make a purchase and then immediately cancel it from the first dialog, it seems as if the callback for the cancel is not getting called. If you then restart the app it seems as if it always works after that, or at least. Same thing with other callbacks, seems as if our store observer isn't listening as the callbacks aren't being registered on the phone. One example of this is if you purchase something, then nothing will happen (if this is the first time the app is launched at least). You get the purchase successful dialog from the app store but it seems as if our own code isn't called. If you then quit the app and restart it the callback gets called. Same problem happens if you for instance try to start a request to download all previous purchases and then immediately cancel it as the first dialog pops up, if you do that then the callback for a failed restore is not called, until you then restart the app and try it again, then it always seems to work. The way we have implemented our store observer is by creating a custom class that's implements the SKPaymentTransactionObserver interface. @interface StoreObserver : NSObject<SKPaymentTransactionObserver> In the class we have implemented the following methods: - (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions - (void)paymentQueueRestoreCompletedTransactionsFinished:(SKPaymentQueue *)queue - (void)paymentQueue:(SKPaymentQueue *)queue restoreCompletedTransactionsFailedWithError:(NSError *)error The way our restore process works is that if you tap on the button that allows you to download all we simply run the restoreCompletedTransactions code as follows: [[SKPaymentQueue defaultQueue] restoreCompletedTransactions]; However, the callback, restoreCompletedTransactionsFailedWithError, which has been implemented in the store observer, does not always get called when we try to cancel the request. This happens when you boot the iPhone / iPod and try this for the first time. If you after that restart the app everything works fine. The StoreObserver class is created when our app is launched, just by running the following code: pStoreObserver = [[StoreObserver alloc] init]; [[SKPaymentQueue defaultQueue] addTransactionObserver:pStoreObserver]; Has anyone else had any similar experiences? Or does anyone have any suggestions on how to solve this? As I said, in the sandbox environment everything was working fine, no issues whatsoever, but now once it's gone live we're experiencing these.

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  • C# : FieldInfo.GetValue returns null

    - by Florian
    Hi and Happy New year ! I've a problem to retrieve my control f2 in the variable o via Reflection : public partial class Form1 : Form { private Form2 f2; public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { Form2 f2 = new Form2(); f2.Show(); } private void button2_Click(object sender, EventArgs e) { Type controlType = this.GetType(); FieldInfo f = controlType.GetField("f2", BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance); object o = f.GetValue(this); // o == null; } } Thank you for your help !

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  • Can't add email signature in Android

    - by user1680411
    I'm trying to compose and send an email which will include a signature at the bottom of my email content in android. I'm able to send an email but I'm not getting the way that allows me to add my own signature. Do you have any suggestion? here's my code: public void addListener() { final Button button = (Button) findViewById(R.id.button1); button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { findViewById = (TextView) findViewById(R.id.t1); Intent i = new Intent(Intent.ACTION_SEND); i.setType("text/plain"); i.putExtra(Intent.EXTRA_EMAIL, new String[] { "[email protected]"}); /*i.putExtra(Intent.EXTRA_CC, new String[] { "[email protected]" });*/ i.putExtra(Intent.EXTRA_SUBJECT, "Android Test"); i.putExtra(Intent.EXTRA_TEXT, "Body"); //i.putExtra(Intent.EXTRA_TEXT, "signature"); try { startActivity(Intent.createChooser(i, "Choose mail app...")); } catch (android.content.ActivityNotFoundException ex) { } } }); }

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  • Does C++ have a proper implementation of interface that does not use vtable?

    - by gilbertc
    Does C++ have a proper implementation of interface that does not use vtable? for example class BaseInterface{ public: virtual void func() const = 0; } class BaseInterfaceImpl:public BaseInterface{ public: void func(){ std::cout<<"called."<<endl; } } BaseInterface* obj = new BaseInterfaceImpl(); obj->func(); the call to func at the last line goes to vtable to find the func ptr of BaseInterfaceImpl::func, but is there any C++ way to do that directly as the BaseInterfaceImpl is not subclassed from any other class besides the pure interface class BaseInterface? Thanks. Gil.

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  • How can I add similar functionality to a number of methods in java?

    - by Roman
    I have a lot of methods for logging, like logSomeAction, logAnotherAction etc. Now I want all these methods make a small pause after printing messages (Thread.sleep). If I do it manually, I would do something like this: //before: public static void logSomeAction () { System.out.println (msg(SOME_ACTION)); } //after: public static void logSomeAction () { System.out.println (msg(SOME_ACTION)); try { Thread.sleep (2000); } catch (InterruptedException ignored) { } } I remember that Java has proxy classes and some other magic-making tools. Is there any way avoid copy-n-pasting N sleep-blocks to N logging methods?

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  • Behavior of nested finally in Exceptions

    - by kuriouscoder
    Hello: Today at work, I had to review a code snippet that looks similar to this mock example. package test; import java.io.IOException; import org.apache.log4j.Logger; public class ExceptionTester { public static Logger logger = Logger.getLogger(ExceptionTester.class); public void test() throws IOException { new IOException(); } public static void main(String[] args) { ExceptionTester comparator = new ExceptionTester(); try { try { comparator.test(); } finally { System.out.println("Finally 1"); } } catch(IOException ex) { logger.error("Exception happened" ex); // also close opened resources } System.out.println("Exiting out of the program"); } } It's printing the following output.I expected an compile error since the inner try did not have a catch block. Finally 1 Exiting out of the program I do not understand why IOException is caught by the outer catch block. I would appreciate if anyone can explain this, especially by citing stack unwinding process

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  • Checking for 2 exepcted values in Junit

    - by Swift-Tuttle
    Hi, I have a java program which throws an exception with 2 different messages for 2 different scenarios and I want the Junit test case to check for equality for both of these messages. As an example - public void amethod() { // do some processing if(scenario1 == true) { throw new MySystemException("An error occured due to case 1 being incorrect."); } else if(scenario2 == true) { throw new MySystemException("An error occured as case 2 could not be found"); } } Now the JUnit for this would be something like- public void testAMethod() { // do something assertEquals("Expected", "Actual"); } As I understand, in this above example, if I use the Scenario1 exception message the junit will fail when an exception is thrown for Scenario2 and vice versa. I would like to know if there is any other way provided in Junit by which I can use this one test method and check for both the messages for the test to pass? Something like an OR, if possible to provide the "Expected" value with both these expected message. I hope my query is clear enough. Thanks

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  • Access outer class from inner class: Why is it done this way?

    - by Vuntic
    So most of us know how to access an outer class from an inner class. Searches with those words give oodles of answered questions on that topic. But what I want to know is why the syntax is the way it is. Example: public class A { private class B { public void c() {A.this.d();} } public void d() {System.out.println("You've called d()! Go, you!");} } Why is it A.this.d()? It looks like this is a static field of class A, but... * am confused * Forgive me if this is a repeat; like I said, searches with those words give how-answers.

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  • Changing background color in Android SDK by clicking a button does not work

    - by DavidNg
    I have a simple program which is able to change the background color after clicking a button, but it does not work public class ChangeBackgroundActivity extends Activity { /** Called when the activity is first created. */ Button blueButton; LinearLayout myLO; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); myLO=(LinearLayout)findViewById(R.layout.main); blueButton=(Button)findViewById(R.id.button1); blueButton.setOnClickListener(new OnClickListener() { public void onClick(View arg0) { // TODO Auto-generated method stub myLO.setBackgroundColor(0x0000FF); //blue color code #0000FF } }); } }

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  • Interface with generic parameters- can't get it to compile

    - by user997112
    I have an interface like so: public interface MyInterface<E extends Something1> { public void meth1(MyClass1<E> x); } and I have a subclass whose superclass implements the above interface: public class MyClass2<E extends Something1> extends Superclass{ public MyClass2(){ } public void meth1(MyClass1 x) { // TODO Auto-generated method stub } } superclass: public abstract class Superclass<E extends Something1> implements MyInterface{ MyClass1<E> x; protected E y; public Superclass(){ } } the problem is that the parameter for meth1() is supposed to be generic. If I do MyClass1 it doesn't like it and the only way I can get it to compile is by leaving out generic parameters- which feels wrong. What's going wrong?

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  • Which Java library lets me initialize an object's properties from a properties file?

    - by Kjetil Ødegaard
    Is there a Java library that lets you "deserialize" a properties file directly into an object instance? Example: say you have a file called init.properties: username=fisk password=frosk and a Java class with some properties: class Connection { private String username; private String password; public void setUsername(String username) { this.username = username; } public void setPassword(String password) { this.password = password; } } I want to do this: Connection c = MagicConfigurator.configure("init.properties", new Connection()) and have MagicConfigurator apply all the values from the properties file to the Connection instance. Is there a library with a class like this?

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  • Second Unit Test Not Running

    - by TomJ
    I am having trouble getting my Method B test to run. The logic is fine, but when the unit tests are run, only Method A will run. If Method A and B are switched in terms of spots, only Method B will run. So clearly the code is wrong at some point. Do I need to call method B's test from inside method A in order to get both unit tests to run? I'm pretty new to C#, so forgive my basic question. using redacted; using Microsoft.VisualStudio.TestTools.UnitTesting; using System; namespace UnitTests { [TestClass()] public class ClassTest { public TestContext TestContext{get;set;} [TestMethod()] public void MethodATest() { the unit test } [TestMethod()] public void MethodBTest() { the unit test } } }

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