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  • C# Object Problem - Can't Solve It

    - by user612041
    I'm getting the error 'Object reference not set to an instance of an object'. I've tried looking at similar problems but genuinely cannot see what the problem is with my program. The line of code that I am having an error with is: labelQuestion.Text = table.Rows[0]["Question"].ToString(); Here is my code in its entirety: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Data.OleDb; using System.Data.Sql; using System.Data.SqlClient; namespace Quiz_Test { public partial class Form1 : Form { public Form1() { InitializeComponent(); } String chosenAnswer, correctAnswer; DataTable table; private void Form1_Load(object sender, EventArgs e) { //declare connection string using windows security string cnString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Users\\Hannah\\Desktop\\QuizQuestions.accdb"; //declare Connection, command and other related objects OleDbConnection conGet = new OleDbConnection(cnString); OleDbCommand cmdGet = new OleDbCommand(); //try //{ //open connection conGet.Open(); //String correctAnswer; cmdGet.CommandType = CommandType.Text; cmdGet.Connection = conGet; cmdGet.CommandText = "SELECT * FROM QuizQuestions ORDER BY rnd()"; OleDbDataReader reader = cmdGet.ExecuteReader(); reader.Read(); labelQuestion.Text = table.Rows[0]["Question"].ToString(); radioButton1.Text = table.Rows[0]["Answer 1"].ToString(); radioButton2.Text = table.Rows[0]["Answer 2"].ToString(); radioButton3.Text = table.Rows[0]["Answer 3"].ToString(); radioButton4.Text = table.Rows[0]["Answer 4"].ToString(); correctAnswer = table.Rows[0]["Correct Answer"].ToString(); ; conGet.Close(); } private void btnSelect_Click(object sender, EventArgs e) { String cnString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Users\\Hannah\\Desktop\\QuizQuestions.accdb"; //declare Connection, command and other related objects OleDbConnection conGet = new OleDbConnection(cnString); OleDbCommand cmdGet = new OleDbCommand(); //try { //open connection conGet.Open(); cmdGet.CommandType = CommandType.Text; cmdGet.Connection = conGet; cmdGet.CommandText = "SELECT * FROM QuizQuestions ORDER BY rnd()"; // select all columns in all rows OleDbDataReader reader = cmdGet.ExecuteReader(); reader.Read(); if (radioButton1.Checked) { chosenAnswer = reader["Answer 1"].ToString(); } else if (radioButton2.Checked) { chosenAnswer = reader["Answer 2"].ToString(); } else if (radioButton3.Checked) { chosenAnswer = reader["Answer 3"].ToString(); } else { chosenAnswer = reader["Answer 4"].ToString(); } if (chosenAnswer == reader["Correct Answer"].ToString()) { //chosenCorrectly++; MessageBox.Show("You have got this answer correct"); //label2.Text = "You have got " + chosenCorrectly + " answers correct"; } else { MessageBox.Show("That is not the correct answer"); } } } } } I realise the problem isn't too big but I can't see how my declaration timings are wrong

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  • How to safely operate on parameters in threads, using C++ & Pthreads?

    - by ChrisCphDK
    Hi. I'm having some trouble with a program using pthreads, where occassional crashes occur, that could be related to how the threads operate on data So I have some basic questions about how to program using threads, and memory layout: Assume that a public class function performs some operations on some strings, and returns the result as a string. The prototype of the function could be like this: std::string SomeClass::somefunc(const std::string &strOne, const std::string &strTwo) { //Error checking of strings have been omitted std::string result = strOne.substr(0,5) + strTwo.substr(0,5); return result; } Is it correct to assume that strings, being dynamic, are stored on the heap, but that a reference to the string is allocated on the stack at runtime? Stack: [Some mem addr] pointer address to where the string is on the heap Heap: [Some mem addr] memory allocated for the initial string which may grow or shrink To make the function thread safe, the function is extended with the following mutex (which is declared as private in the "SomeClass") locking: std::string SomeClass::somefunc(const std::string &strOne, const std::string &strTwo) { pthread_mutex_lock(&someclasslock); //Error checking of strings have been omitted std::string result = strOne.substr(0,5) + strTwo.substr(0,5); pthread_mutex_unlock(&someclasslock); return result; } Is this a safe way of locking down the operations being done on the strings (all three), or could a thread be stopped by the scheduler in the following cases, which I'd assume would mess up the intended logic: a. Right after the function is called, and the parameters: strOne & strTwo have been set in the two reference pointers that the function has on the stack, the scheduler takes away processing time for the thread and lets a new thread in, which overwrites the reference pointers to the function, which then again gets stopped by the scheduler, letting the first thread back in? b. Can the same occur with the "result" string: the first string builds the result, unlocks the mutex, but before returning the scheduler lets in another thread which performs all of it's work, overwriting the result etc. Or are the reference parameters / result string being pushed onto the stack while another thread is doing performing it's task? Is the safe / correct way of doing this in threads, and "returning" a result, to pass a reference to a string that will be filled with the result instead: void SomeClass::somefunc(const std::string &strOne, const std::string &strTwo, std::string result) { pthread_mutex_lock(&someclasslock); //Error checking of strings have been omitted result = strOne.substr(0,5) + strTwo.substr(0,5); pthread_mutex_unlock(&someclasslock); } The intended logic is that several objects of the "SomeClass" class creates new threads and passes objects of themselves as parameters, and then calls the function: "someFunc": int SomeClass::startNewThread() { pthread_attr_t attr; pthread_t pThreadID; if(pthread_attr_init(&attr) != 0) return -1; if(pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED) != 0) return -2; if(pthread_create(&pThreadID, &attr, proxyThreadFunc, this) != 0) return -3; if(pthread_attr_destroy(&attr) != 0) return -4; return 0; } void* proxyThreadFunc(void* someClassObjPtr) { return static_cast<SomeClass*> (someClassObjPtr)->somefunc("long string","long string"); } Sorry for the long description. But I hope the questions and intended purpose is clear, if not let me know and I'll elaborate. Best regards. Chris

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  • Programmatically adding an object and selecting the correspondig row does not make it become the CurrentRow

    - by Robert
    I'm in a struggle with the DataGridView: I do have a BindingList of some simple objects that implement INotifyPropertyChanged. The DataGridView's datasource is set to this BindingList. Now I need to add an object to the list by hitting the "+" key. When an object is added, it should appear as a new row and it shall become the current row. As the CurrentRow-property is readonly, I iterate through all rows, check if its bound item is the newly created object, and if it is, I set this row to "Selected = true;" The problem: although the new object and thereby a new row gets inserted and selected in the DataGridView, it still is not the CurrentRow! It does not become the CurrentRow unless I do a mouse click into this new row. In this test program you can add new objects (and thereby rows) with the "+" key, and with the "i" key the data-bound object of the CurrentRow is shown in a MessageBox. How can I make a newly added object become the CurrentObject? Thanks for your help! Here's the sample: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace WindowsFormsApplication1 { public partial class Form1 : Form { BindingList<item> myItems; public Form1() { InitializeComponent(); myItems = new BindingList<item>(); for (int i = 1; i <= 10; i++) { myItems.Add(new item(i)); } dataGridView1.DataSource = myItems; } public void Form1_KeyDown(object sender, KeyEventArgs e) { if (e.KeyCode == Keys.Add) { addItem(); } } public void addItem() { item i = new item(myItems.Count + 1); myItems.Add(i); foreach (DataGridViewRow dr in dataGridView1.Rows) { if (dr.DataBoundItem == i) { dr.Selected = true; } } } private void btAdd_Click(object sender, EventArgs e) { addItem(); } private void dataGridView1_KeyDown(object sender, KeyEventArgs e) { if (e.KeyCode == Keys.Add) { addItem(); } if (e.KeyCode == Keys.I) { MessageBox.Show(((item)dataGridView1.CurrentRow.DataBoundItem).title); } } } public class item : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; private int _id; public int id { get { return _id; } set { this.title = "This is item number " + value.ToString(); _id = value; InvokePropertyChanged(new PropertyChangedEventArgs("id")); } } private string _title; public string title { get { return _title; } set { _title = value; InvokePropertyChanged(new PropertyChangedEventArgs("title")); } } public item(int id) { this.id = id; } #region Implementation of INotifyPropertyChanged public void InvokePropertyChanged(PropertyChangedEventArgs e) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) handler(this, e); } #endregion } }

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  • What is a good java data structure for storing nested items (like cities in states)?

    - by anotherAlan
    I'm just getting started in Java and am looking for advice on a good way to store nested sets of data. For example, I'm interested in storing city population data that can be accessed by looking up the city in a given state. (Note: eventually, other data will be stored with each city as well, this is just the first attempt at getting started.) The current approach I'm using is to have a StateList Object which contains a HashMap that stores State Objects via a string key (i.e. HashMap<String, State>). Each State Object contains its own HashMap of City Objects keyed off the city name (i.e. HashMap<String, City>). A cut down version of what I've come up with looks like this: // TestPopulation.java public class TestPopulation { public static void main(String [] args) { // build the stateList Object StateList sl = new StateList(); // get a test state State stateAl = sl.getState("AL"); // make sure it's there. if(stateAl != null) { // add a city stateAl.addCity("Abbeville"); // now grab the city City cityAbbevilleAl = stateAl.getCity("Abbeville"); cityAbbevilleAl.setPopulation(2987); System.out.print("The city has a pop of: "); System.out.println(Integer.toString(cityAbbevilleAl.getPopulation())); } // otherwise, print an error else { System.out.println("That was an invalid state"); } } } // StateList.java import java.util.*; public class StateList { // define hash map to hold the states private HashMap<String, State> theStates = new HashMap<String, State>(); // setup constructor that loads the states public StateList() { String[] stateCodes = {"AL","AK","AZ","AR","CA","CO"}; // etc... for (String s : stateCodes) { State newState = new State(s); theStates.put(s, newState); } } // define method for getting a state public State getState(String stateCode) { if(theStates.containsKey(stateCode)) { return theStates.get(stateCode); } else { return null; } } } // State.java import java.util.*; public class State { // Setup the state code String stateCode; // HashMap for cities HashMap<String, City> cities = new HashMap<String, City>(); // define the constructor public State(String newStateCode) { System.out.println("Creating State: " + newStateCode); stateCode = newStateCode; } // define the method for adding a city public void addCity(String newCityName) { City newCityObj = new City(newCityName); cities.put(newCityName, newCityObj); } // define the method for getting a city public City getCity(String cityName) { if(cities.containsKey(cityName)) { return cities.get(cityName); } else { return null; } } } // City.java public class City { // Define the instance vars String cityName; int cityPop; // setup the constructor public City(String newCityName) { cityName = newCityName; System.out.println("Created City: " + newCityName); } public void setPopulation(int newPop) { cityPop = newPop; } public int getPopulation() { return cityPop; } } This is working for me, but I'm wondering if there are gotchas that I haven't run into, or if there are alternate/better ways to do the same thing. (P.S. I know that I need to add some more error checking in, but right now, I'm focused on trying to figure out a good data structure.) (NOTE: Edited to change setPop() and getPop() to setPopulation() and getPopulation() respectively to avoid confucsion)

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  • Referencing variables in a structure / C++

    - by user1628622
    Below, I provided a minimal example of code I created. I managed to get this code working, but I'm not sure if the practice being employed is sound. In essence, what I am trying to do is have the 'Parameter' class reference select elements in the 'States' class, so variables in States can be changed via Parameters. Questions I have: is the approach taken OK? If not, is there a better way to achieve what I am aiming for? Example code: struct VAR_TYPE{ public: bool is_fixed; // If is_fixed = true, then variable is a parameter double value; // Numerical value std::string name; // Description of variable (to identify it by name) }; struct NODE{ public: VAR_TYPE X, Y, Z; /* VAR_TYPE is a structure of primitive types */ }; class States{ private: std::vector <NODE_ptr> node; // shared ptr to struct NODE std::vector <PROP_DICTIONARY_ptr> property; // CAN NOT be part of Parameter std::vector <ELEMENT_ptr> element; // CAN NOT be part of Parameter public: /* ect */ void set_X_reference ( Parameter &T , int i ) { T.push_var( &node[i]->X ); } void set_Y_reference ( Parameter &T , int i ) { T.push_var( &node[i]->Y ); } void set_Z_reference ( Parameter &T , int i ) { T.push_var( &node[i]->Z ); } bool get_node_bool_X( int i ) { return node[i]->X.is_fixed; } // repeat for Y and Z }; class Parameter{ private: std::vector <VAR_TYPE*> var; public: /* ect */ }; int main(){ States S; Parameter P; /* Here I initialize and set S, and do other stuff */ // Now I assign components in States to Parameters for(int n=0 ; n<S.size_of_nodes() ; n++ ){ if ( S.get_node_bool_X(n)==true ){ S.set_X_reference ( P , n ); }; // repeat if statement for Y and Z }; /* Now P points selected to data in S, and I can * modify the contents of S through P */ return 0; }; Update The reason this issue cropped up is I am working with Fortran legacy code. To sum up this Fotran code - it's a numerical simulation of a flight vehicle. This code has a fairly rigid procedural framework one must work within, which comes with a pre-defined list of allowable Fortran types. The Fortran glue code can create an instance of a C++ object (in actuality, a reference from the perspective of Fortran), but is not aware what is contained in it (other means are used to extract C++ data into Fortran). The problem that I encountered is when a C++ module is dynamically linked to the Fortran glue code, C++ objects have to be initialized each instance the C++ code is called. This happens by virtue of how the Fortran template is defined. To avoid this cycle of re-initializing objects, I plan to use 'State' as a container class. The Fortran code allows a 'State' object, which has an arbitrary definition; but I plan to use it to harness all relevant information about the model. The idea is to use the Parameters class (which is exposed and updated by the Fortran code) to update variables in States.

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  • what does square bracket syntax mean above a method in C#, ASP.NET

    - by Alexander
    I am just looking a bunch of codes that I am trying to learn from an open source project and sometimes I see a square brackets above a function such as: [EdmFunction("NerdDinnerModel.Store", "DistanceBetween")] public static double DistanceBetween(double lat1, double long1, double lat2, double long2) or [Bind(Include = "Title,Description,EventDate,Address,Country,ContactPhone,Latitude,Longitude")] [MetadataType(typeof(Dinner_Validation))] public partial class Dinner

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  • JPA exception: Object: ... is not a known entity type.

    - by Toto
    I'm new to JPA and I'm having problems with the autogeneration of primary key values. I have the following entity: package jpatest.entities; import java.io.Serializable; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; @Entity public class MyEntity implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; public Long getId() { return id; } public void setId(Long id) { this.id = id; } private String someProperty; public String getSomeProperty() { return someProperty; } public void setSomeProperty(String someProperty) { this.someProperty = someProperty; } public MyEntity() { } public MyEntity(String someProperty) { this.someProperty = someProperty; } @Override public String toString() { return "jpatest.entities.MyEntity[id=" + id + "]"; } } and the following main method in other class: public static void main(String[] args) { EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPATestPU"); EntityManager em = emf.createEntityManager(); em.getTransaction().begin(); MyEntity e = new MyEntity("some value"); em.persist(e); /* (exception thrown here) */ em.getTransaction().commit(); em.close(); emf.close(); } This is my persistence unit: <?xml version="1.0" encoding="UTF-8"?> <persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"> <persistence-unit name="JPATestPU" transaction-type="RESOURCE_LOCAL"> <provider>oracle.toplink.essentials.PersistenceProvider</provider> <class>jpatest.entities.MyEntity</class> <properties> <property name="toplink.jdbc.user" value="..."/> <property name="toplink.jdbc.password" value="..."/> <property name="toplink.jdbc.url" value="jdbc:mysql://localhost:3306/jpatest"/> <property name="toplink.jdbc.driver" value="com.mysql.jdbc.Driver"/> <property name="toplink.ddl-generation" value="create-tables"/> </properties> </persistence-unit> </persistence> When I execute the program I get the following exception in the line marked with the proper comment: Exception in thread "main" java.lang.IllegalArgumentException: Object: jpatest.entities.MyEntity[id=null] is not a known entity type. at oracle.toplink.essentials.internal.sessions.UnitOfWorkImpl.registerNewObjectForPersist(UnitOfWorkImpl.java:3212) at oracle.toplink.essentials.internal.ejb.cmp3.base.EntityManagerImpl.persist(EntityManagerImpl.java:205) at jpatest.Main.main(Main.java:...) What am I missing?

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  • Include WordPress Content Outside of WordPress

    - by S Pangborn
    I'm looking to build a mobile version of a WordPress site and have most of it built in static files, but am trying to get access to the WordPress content from inside an external PHP file that the mobile site will run from. How can I get access to the loop or database without manually writing SQL queries?

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  • Deploying MVC2 application to IIS7.5 - Ninject asked to provide controllers for content files

    - by Rune Jacobsen
    I have an application that started life as an MVC (1.0) app in Visual Studio 2008 Sp1 with a bunch of Silverlight 3 projects as part of the site. Nothing fancy at all. Using Ninject for dependency injection (first version 2 beta, now the released version 2 with the MVC extensions). With the release of .Net 4.0, VS2010, MVC2 etc., we decided to move the application to the newest platform. The conversion wizard in VS2010 apparently took care of everything, with one exception - it didn't change references to mvc1 to now point to mvc2, so I had to do that manually. Of course, this makes me think about other MVC2 things that could be missing from my app, that would be there if I did File - New Project... But that is not the focus of this question. When I deploy this application to the IIS 7.5 server (running on Win2008 R2 x64), the application as such works. However, images, scripts and other static content doesn't seem to exist. Of course they are there on disk on the server, but they don't show up in the client web browser. I am fairly new to IIS, so the only trick I knew is to try to open the web page in a browser on the server, as that could give me more information. And here, finally, we meet our enemy. If I try to go directly to the URL of one of the images (http://server/Content/someimage.jpg for instance), I get the following error in the browser: The IControllerFactory 'Ninject.Web.Mvc.NinjectControllerFactory' did not return a controller for a controller named 'Content'. Aha. The web server tries to feed this request to MVC, who with its' default routing setup assumes Content to be a controller, and fails. How can I get it to treat Content/ and Scripts/ (among others) as non-controllers and just pass through the static content? This of course works with Cassini on my developer machine, but as soon as I deploy, this problem hits. I am using the last version of Ninject MVC 2 where the IoC tool should pass missing controllers to the base controller factory, but this has apparently not helped. I have also tried to add ignore routes for Content etc., but this apparently has no effect either. I am not even sure I am addressing the problem on the right level. Does anyone know where to look to get this app going? I have full control of the web server so I can more or less do whatever I want to it, as long as it starts working. Thanks!

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  • Find kth smallest element in a binary search tree in Optimum way

    - by Bragaadeesh
    Hi, I need to find the kth smallest element in the binary search tree without using any static/global variable. How to achieve it efficiently? The solution that I have in my mind is doing the operation in O(n), the worst case since I am planning to do an inorder traversal of the entire tree. But deep down I feel that I am not using the BST property here. Is my assumptive solution correct or is there a better one available ?

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  • How to install wkhtmltopdf on a linux based web server

    - by Yogi Yang 007
    I have tried in all ways to get wkhtmltopdf installed on our web server but unfortunately it is not getting installed. I cannot access user/bin folder as stated in a tutorial on installation. On the server in public_html folder there is a sub folder _vti_bin, I copied the file wkhtmltopdf-i386 from wkhtmltopdf-0.9.1-static-i386, but I am not able to execute it. How to install wkhtmltopdf on (shared hosting) web server and get it working?

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  • These are few objective type questions which i was not able to find the solution [closed]

    - by Tarun
    1. Which of the following advantages does System.Collections.IDictionaryEnumerator provide over System.Collections.IEnumerator? a. It adds properties for direct access to both the Key and the Value b. It is optimized to handle the structure of a Dictionary. c. It provides properties to determine if the Dictionary is enumerated in Key or Value order d. It provides reverse lookup methods to distinguish a Key from a specific Value 2. When Implementing System.EnterpriseServices.ServicedComponent derived classes, which of the following statements are true? a. Enabling object pooling requires an attribute on the class and the enabling of pooling in the COM+ catalog. b. Methods can be configured to automatically mark a transaction as complete by the use of attributes. c. You can configure authentication using the AuthenticationOption when the ActivationMode is set to Library. d. You can control the lifecycle policy of an individual instance using the SetLifetimeService method. 3. Which of the following are true regarding event declaration in the code below? class Sample { event MyEventHandlerType MyEvent; } a. MyEventHandlerType must be derived from System.EventHandler or System.EventHandler<TEventArgs> b. MyEventHandlerType must take two parameters, the first of the type Object, and the second of a class derived from System.EventArgs c. MyEventHandlerType may have a non-void return type d. If MyEventHandlerType is a generic type, event declaration must use a specialization of that type. e. MyEventHandlerType cannot be declared static 4. Which of the following statements apply to developing .NET code, using .NET utilities that are available with the SDK or Visual Studio? a. Developers can create assemblies directly from the MSIL Source Code. b. Developers can examine PE header information in an assembly. c. Developers can generate XML Schemas from class definitions contained within an assembly. d. Developers can strip all meta-data from managed assemblies. e. Developers can split an assembly into multiple assemblies. 5. Which of the following characteristics do classes in the System.Drawing namespace such as Brush,Font,Pen, and Icon share? a. They encapsulate native resource and must be properly Disposed to prevent potential exhausting of resources. b. They are all MarshalByRef derived classes, but functionality across AppDomains has specific limitations. c. You can inherit from these classes to provide enhanced or customized functionality 6. Which of the following are required to be true by objects which are going to be used as keys in a System.Collections.HashTable? a. They must handle case-sensitivity identically in both the GetHashCode() and Equals() methods. b. Key objects must be immutable for the duration they are used within a HashTable. c. Get HashCode() must be overridden to provide the same result, given the same parameters, regardless of reference equalityl unless the HashTable constructor is provided with an IEqualityComparer parameter. d. Each Element in a HashTable is stored as a Key/Value pair of the type System.Collections.DictionaryElement e. All of the above 7. Which of the following are true about Nullable types? a. A Nullable type is a reference type. b. A Nullable type is a structure. c. An implicit conversion exists from any non-nullable value type to a nullable form of that type. d. An implicit conversion exists from any nullable value type to a non-nullable form of that type. e. A predefined conversion from the nullable type S? to the nullable type T? exists if there is a predefined conversion from the non-nullable type S to the non-nullable type T 8. When using an automatic property, which of the following statements is true? a. The compiler generates a backing field that is completely inaccessible from the application code. b. The compiler generates a backing field that is a private instance member with a leading underscore that can be programmatically referenced. c. The compiler generates a backing field that is accessible via reflection d. The compiler generates a code that will store the information separately from the instance to ensure its security. 9. Which of the following does using Initializer Syntax with a collection as shown below require? CollectionClass numbers = new CollectionClass { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; a. The Collection Class must implement System.Collections.Generic.ICollection<T> b. The Collection Class must implement System.Collections.Generic.IList<T> c. Each of the Items in the Initializer List will be passed to the Add<T>(T item) method d. The items in the initializer will be treated as an IEnumerable<T> and passed to the collection constructor+K110 10. What impact will using implicitly typed local variables as in the following example have? var sample = "Hello World"; a. The actual type is determined at compilation time, and has no impact on the runtime b. The actual type is determined at runtime, and late binding takes effect c. The actual type is based on the native VARIANT concept, and no binding to a specific type takes place. d. "var" itself is a specific type defined by the framework, and no special binding takes place 11. Which of the following is not supported by remoting object types? a. well-known singleton b. well-known single call c. client activated d. context-agile 12. In which of the following ways do structs differ from classes? a. Structs can not implement interfaces b. Structs cannot inherit from a base struct c. Structs cannot have events interfaces d. Structs cannot have virtual methods 13. Which of the following is not an unboxing conversion? a. void Sample1(object o) { int i = (int)o; } b. void Sample1(ValueType vt) { int i = (int)vt; } c. enum E { Hello, World} void Sample1(System.Enum et) { E e = (E) et; } d. interface I { int Value { get; set; } } void Sample1(I vt) { int i = vt.Value; } e. class C { public int Value { get; set; } } void Sample1(C vt) { int i = vt.Value; } 14. Which of the following are characteristics of the System.Threading.Timer class? a. The method provided by the TimerCallback delegate will always be invoked on the thread which created the timer. b. The thread which creates the timer must have a message processing loop (i.e. be considered a UI thread) c. The class contains protection to prevent reentrancy to the method provided by the TimerCallback delegate d. You can receive notification of an instance being Disposed by calling an overload of the Dispose method. 15. What is the proper declaration of a method which will handle the following event? Class MyClass { public event EventHandler MyEvent; } a. public void A_MyEvent(object sender, MyArgs e) { } b. public void A_MyEvent(object sender, EventArgs e) { } c. public void A_MyEvent(MyArgs e) { } d. public void A_MyEvent(MyClass sender,EventArgs e) { } 16. Which of the following scenarios are applicable to Window Workflow Foundation? a. Document-centric workflows b. Human workflows c. User-interface page flows d. Builtin support for communications across multiple applications and/or platforms e. All of the above 17. When using an automatic property, which of the following statements is true? a. The compiler generates a backing field that is completely inaccessible from the application code. b. The compiler generates a backing field that is a private instance member with a leading underscore that can be programmatically referenced. c. The compiler generates a backing field that is accessible via reflection d. The compiler generates a code that will store the information separately from the instance to ensure its security. 18 While using the capabilities supplied by the System.Messaging classes, which of the following are true? a. Information must be explicitly converted to/from a byte stream before it uses the MessageQueue class b. Invoking the MessageQueue.Send member defaults to using the System.Messaging.XmlMessageFormatter to serialize the object. c. Objects must be XMLSerializable in order to be transferred over a MessageQueue instance. d. The first entry in a MessageQueue must be removed from the queue before the next entry can be accessed e. Entries removed from a MessageQueue within the scope of a transaction, will be pushed back into the front of the queue if the transaction fails. 19. Which of the following are true about declarative attributes? a. They must be inherited from the System.Attribute. b. Attributes are instantiated at the same time as instances of the class to which they are applied. c. Attribute classes may be restricted to be applied only to application element types. d. By default, a given attribute may be applied multiple times to the same application element. 20. When using version 3.5 of the framework in applications which emit a dynamic code, which of the following are true? a. A Partial trust code can not emit and execute a code b. A Partial trust application must have the SecurityCriticalAttribute attribute have called Assert ReflectionEmit permission c. The generated code no more permissions than the assembly which emitted it. d. It can be executed by calling System.Reflection.Emit.DynamicMethod( string name, Type returnType, Type[] parameterTypes ) without any special permissions Within Windows Workflow Foundation, Compensating Actions are used for: a. provide a means to rollback a failed transaction b. provide a means to undo a successfully committed transaction later c. provide a means to terminate an in process transaction d. achieve load balancing by adapting to the current activity 21. What is the proper declaration of a method which will handle the following event? Class MyClass { public event EventHandler MyEvent; } a. public void A_MyEvent(object sender, MyArgs e) { } b. public void A_MyEvent(object sender, EventArgs e) { } c. public void A_MyEvent(MyArgs e) { } d. public void A_MyEvent(MyClass sender,EventArgs e) { } 22. Which of the following controls allows the use of XSL to transform XML content into formatted content? a. System.Web.UI.WebControls.Xml b. System.Web.UI.WebControls.Xslt c. System.Web.UI.WebControls.Substitution d. System.Web.UI.WebControls.Transform 23. To which of the following do automatic properties refer? a. You declare (explicitly or implicitly) the accessibility of the property and get and set accessors, but do not provide any implementation or backing field b. You attribute a member field so that the compiler will generate get and set accessors c. The compiler creates properties for your class based on class level attributes d. They are properties which are automatically invoked as part of the object construction process 24. Which of the following are true about Nullable types? a. A Nullable type is a reference type. b. An implicit conversion exists from any non-nullable value type to a nullable form of that type. c. A predefined conversion from the nullable type S? to the nullable type T? exists if there is a predefined conversion from the non-nullable type S to the non-nullable type T 25. When using an automatic property, which of the following statements is true? a. The compiler generates a backing field that is completely inaccessible from the application code. b. The compiler generates a backing field that is accessible via reflection. c. The compiler generates a code that will store the information separately from the instance to ensure its security. 26. When using an implicitly typed array, which of the following is most appropriate? a. All elements in the initializer list must be of the same type. b. All elements in the initializer list must be implicitly convertible to a known type which is the actual type of at least one member in the initializer list c. All elements in the initializer list must be implicitly convertible to common type which is a base type of the items actually in the list 27. Which of the following is false about anonymous types? a. They can be derived from any reference type. b. Two anonymous types with the same named parameters in the same order declared in different classes have the same type. c. All properties of an anonymous type are read/write. 28. Which of the following are true about Extension methods. a. They can be declared either static or instance members b. They must be declared in the same assembly (but may be in different source files) c. Extension methods can be used to override existing instance methods d. Extension methods with the same signature for the same class may be declared in multiple namespaces without causing compilation errors

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  • Can I read an Outlook (2003/2007) PST file in C#?

    - by Andy May
    Is it possible to read a .PST file using C#? I would like to do this as a standalone application, not as an Outlook addin (if that is possible). If have seen other SO questions similar to this mention MailNavigator but I am looking to do this programmatically in C#. I have looked at the Microsoft.Office.Interop.Outlook namespace but that appears to be just for Outlook addins. LibPST appears to be able to read PST files, but this is in C (sorry Joel, I didn't learn C before graduating). Any help would be greatly appreciated, thanks! EDIT: Thank you all for the responses! I accepted Matthew Ruston's response as the answer because it ultimately led me to the code I was looking for. Here is a simple example of what I got to work (You will need to add a reference to Microsoft.Office.Interop.Outlook): using System; using System.Collections.Generic; using Microsoft.Office.Interop.Outlook; namespace PSTReader { class Program { static void Main () { try { IEnumerable<MailItem> mailItems = readPst(@"C:\temp\PST\Test.pst", "Test PST"); foreach (MailItem mailItem in mailItems) { Console.WriteLine(mailItem.SenderName + " - " + mailItem.Subject); } } catch (System.Exception ex) { Console.WriteLine(ex.Message); } Console.ReadLine(); } private static IEnumerable<MailItem> readPst(string pstFilePath, string pstName) { List<MailItem> mailItems = new List<MailItem>(); Application app = new Application(); NameSpace outlookNs = app.GetNamespace("MAPI"); // Add PST file (Outlook Data File) to Default Profile outlookNs.AddStore(pstFilePath); MAPIFolder rootFolder = outlookNs.Stores[pstName].GetRootFolder(); // Traverse through all folders in the PST file // TODO: This is not recursive, refactor Folders subFolders = rootFolder.Folders; foreach (Folder folder in subFolders) { Items items = folder.Items; foreach (object item in items) { if (item is MailItem) { MailItem mailItem = item as MailItem; mailItems.Add(mailItem); } } } // Remove PST file from Default Profile outlookNs.RemoveStore(rootFolder); return mailItems; } } } Note: This code assumes that Outlook is installed and already configured for the current user. It uses the Default Profile (you can edit the default profile by going to Mail in the Control Panel). One major improvement on this code would be to create a temporary profile to use instead of the Default, then destroy it once completed.

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  • CollectionViewSource.GetDefaultView is not in Silverlight 3! What's the work-around?

    - by rasx
    The CollectionViewSource.GetDefaultView() method is not in Silverlight 3. In WPF I have this extension method: public static void SetActiveViewModel<ViewModelType>(this ViewModelBase viewModel, ViewModelType collectionItem, ObservableCollection<ViewModelType> collection) where ViewModelType : ViewModelBase { Debug.Assert(collection.Contains(collectionItem)); ICollectionView collectionView = CollectionViewSource.GetDefaultView(collection); if(collectionView != null) collectionView.MoveCurrentTo(collectionItem); } How can this be written in Silverlight 3?

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  • Memory leak with Microsoft.JScript.Eval.JScriptEvaluate?

    - by Dmi
    I'm evaluating some javascript with Microsoft.JScript.Eval.JScriptEvaluate() and I noticed from my memory profiler that there are a large number of System.String left allocated by Microsoft.JScript.HashtableEntry. Microsoft.JScript.Eval is a static class, does anyone know what class is holding these instances and how I can clear them?

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  • Getting problem while capturing image through web cam in Java -OpenCV code.

    - by Chetan
    Hi.. I am developing Face detector using OpenCV library in java... I have written sample code for this,but it is giving Error while capturing image. can any one help please. Here is the code import java.awt.; import java.awt.event.; import java.awt.image.MemoryImageSource; import hypermedia.video.OpenCV; @SuppressWarnings("serial") public class FaceDetection extends Frame implements Runnable { ///Main method. public static void main(String[] args) { //System.out.println( "\nOpenCV face detection sample\n" ); new FaceDetection(); } // program execution frame rate (millisecond) final int FRAME_RATE = 1000/30; OpenCV cv = null; // OpenCV Object Thread t = null; // the sample thread // the input video stream image Image frame = null; // list of all face detected area Rectangle[] squares = new Rectangle[0]; //** Setup Frame and Object(s). FaceDetection() { super( "Face Detection" ); // OpenCV setup cv = new OpenCV(); //cv.capture(1, 1, 100); cv.capture( 320, 240 ); cv.cascade( OpenCV.CASCADE_FRONTALFACE_ALT ); // frame setup this.setBounds( 100, 100, cv.width, cv.height ); this.setBackground( Color.BLACK ); this.setVisible( true ); this.addKeyListener( new KeyAdapter() { public void keyReleased( KeyEvent e ) { if ( e.getKeyCode()==KeyEvent.VK_ESCAPE ) { // ESC : release OpenCV resources cv.dispose(); System.exit(0); } } } ); // start running program t = new Thread( this ); t.start(); } // Draw video frame and each detected faces area. public void paint( Graphics g ) { // draw image g.drawImage( frame, 0, 0, null ); // draw squares g.setColor( Color.RED ); for( Rectangle rect : squares ) g.drawRect( rect.x, rect.y, rect.width, rect.height ); } @SuppressWarnings("static-access") public void run() { while( t!=null && cv!=null ) { try { t.sleep( FRAME_RATE ); // grab image from video stream cv.read(); // create a new image from cv pixels data MemoryImageSource mis = new MemoryImageSource( cv.width, cv.height, cv.pixels(), 0, cv.width ); frame = createImage( mis ); // detect faces squares = cv.detect( 1.2f, 2, OpenCV.HAAR_DO_CANNY_PRUNING, 20, 20 ); // of course, repaint repaint(); } catch( InterruptedException e ) {;} } } } Error while starting capture : device 0

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  • Creating WCF Services using Dynamic Languages and DLR

    - by Perpetualcoder
    I was curious how anyone would go about creating WCF based services using a dynamic language like IronPython or IronRuby. These languages do not have the concept of interfaces. How would someone define service contracts? Would we need to rely on static languages for such kind of tasks? I am a big fan of Python in particular and would like to know if this can be done at this point.

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  • What does the filter parameter to createScaledBitmap do?

    - by clahey
    The declaration of android.graphics.Bitmap.createScaledBitmap is public static Bitmap createScaledBitmap (Bitmap src, int dstWidth, int dstHeight, boolean filter) However, the documentation doesn't explain any of the parameters. All of them are pretty obvious except for boolean filter. Does anyone know what it does?

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  • AccessViolationException, attempted to read or write protected memory

    - by Malfist
    I'm using a dll that contains unsafe code for interacting with specific hardware, and I'm trying to use it from C#, but I keep getting an AccessViolationException. What's causing it, and how can I fix it? namespace FingerPrint { public unsafe partial class Form1 : Form { [DllImport("MyDll.dll")] public static extern int DoesExist(); public unsafe Form1() { InitializeComponent(); MessageBox.Show(DoesExist() + ""); } } }

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  • Specify the search path for DllImport in .NET

    - by Stefan
    Is there a way to specify the paths to be searched for a given assembly that is imported with DllImport? [DllImport("MyDll.dll")] static extern void Func(); This will search for the dll in the app dir and in the PATH environment variable. But at times the dll will be placed elsewhere. Can this information be specified in app.config or manifest file to avoid dynamic loading and dynamic invocation?

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  • Android sending lots of SMS messages

    - by Robert Parker
    I have a app, which sends a lot of SMS messages to a central server. Each user will probably send ~300 txts/day. SMS messages are being used as a networking layer, because SMS is almost everywhere and mobile internet is not. The app is intended for use in a lot of 3rd world countries where mobile internet is not ubiquitous. When I hit a limit of 100 messages, I get a prompt for each message sent. The prompt says "A large number of SMS messages are being sent". This is not ok for the user to get prompted each time to ask if the app can send a text message. The user doesn't want to get 30 consecutive prompts. I found this android source file with google. It could be out of date, I can't tell. It looks like there is a limit of 100 sms messages every 3600000ms(1 day) for each application. http://www.netmite.com/android/mydroid/frameworks/base/telephony/java/com/android/internal/telephony/gsm/SMSDispatcher.java /** Default checking period for SMS sent without uesr permit */ private static final int DEFAULT_SMS_CHECK_PERIOD = 3600000; /** Default number of SMS sent in checking period without uesr permit */ private static final int DEFAULT_SMS_MAX_ALLOWED = 100; and /** * Implement the per-application based SMS control, which only allows * a limit on the number of SMS/MMS messages an app can send in checking * period. */ private class SmsCounter { private int mCheckPeriod; private int mMaxAllowed; private HashMap<String, ArrayList<Long>> mSmsStamp; /** * Create SmsCounter * @param mMax is the number of SMS allowed without user permit * @param mPeriod is the checking period */ SmsCounter(int mMax, int mPeriod) { mMaxAllowed = mMax; mCheckPeriod = mPeriod; mSmsStamp = new HashMap<String, ArrayList<Long>> (); } boolean check(String appName) { if (!mSmsStamp.containsKey(appName)) { mSmsStamp.put(appName, new ArrayList<Long>()); } return isUnderLimit(mSmsStamp.get(appName)); } private boolean isUnderLimit(ArrayList<Long> sent) { Long ct = System.currentTimeMillis(); Log.d(TAG, "SMS send size=" + sent.size() + "time=" + ct); while (sent.size() > 0 && (ct - sent.get(0)) > mCheckPeriod ) { sent.remove(0); } if (sent.size() < mMaxAllowed) { sent.add(ct); return true; } return false; } } Is this even the real android code? It looks like it is in the package "com.android.internal.telephony.gsm", I can't find this package on the android website. How can I disable/modify this limit? I've been googling for solutions, but I haven't found anything.

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  • Why primefaces runs in Mozilla only?

    - by Sarang
    Hello all, I have used Prime Faces in my project. It allows to run only in Mozilla with use of static data. But, it doesn't give any output in Google Chrome ! What is the reason for it? Please reply. With Regards, Sarang Dave

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  • Help with regex to detect urls in a string

    - by Ali Taha Ali Mahboub
    Hi guys i found this regex to detect urls in a string and wraps them inside the tag public static String detectUrls(String text) { String newText = text .replaceAll("(?<!http://)www\\.[\\w/%.\\-?&=]+", "http://$0") .replaceAll("(?:https?|ftps?|http?)://[\\w/%.\\-?&=]+", "<a href='$0'>$0</a>"); return newText; } but this regex doesn't work with the following pattern: https://www.myserver.com so please advise.

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  • FBML tag to detect user language in a tab

    - by Pierre Olivier Martel
    I have a custom tab for a fan page that need to display a JPEG image. I have an image in English and one in French. Is there a way to detect the user locale in FBML to display the right image? I know how to do this server side using the Facebook fb_sig_locale param but I was planning on just using the Static FBML app which is much simpler than setting up a whole custom application.

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