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  • Properties are making trouble

    - by DhavalR
    In my application I have added a Properties.cs file which contains properties that I am would use through out the application. I am getting NullReferenceException = Object reference not set to an instance of an object. Here is the code for Properties.cs public class Properties { private static string type1; public static string Type1 { get { return type1; } set { type1= value; } } } And when I access this property in one of my form I am getting error. e.g. if (Properties.Type1.Equals(string.Empty) || Properties.Type1.Equals(null)) { //// Do something }

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  • Problem showing selected value of combobox when it is bind to a List<T> using Linq to Entities

    - by Syed Mustehsan Ikram
    I have a combobox which is has itemtemplate applied on it and is bind to a List of entity return using linq. i m using mvvm. It is bind to it successfully but when i set the selected value of it from code at runtime to show the selected value coming from db it doesn't select it. For reference here is my combobox xaml. SelectedValue="{Binding Path=SelectedManufacturer}" Grid.Column="3" Grid.Row="2" Margin="20,9.25,68,7.75" ItemTemplate="{StaticResource ManufacturerDataTemplate}" TabIndex="6"/ Here is my part from code behind from viewModel. List currentManufacturers = new List(); tblManufacturer selectedManufacturer = null; public List CurrentManufacturers { get { return currentManufacturers; } set { currentManufacturers = value; NotifyPropertyChanged("CurrentManufacturers"); } } public tblManufacturer SelectedManufacturer { get { return selectedManufacturer; } set { selectedManufacturer = currentManufacturers.Where(mm => mm.ManufacturerID == Convert.ToInt32(selectedDevice.tblManufacturer.EntityKey.EntityKeyValues[0].Value)).First(); NotifyPropertyChanged("SelectedManufacturer"); } }

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  • Printing out series of numbers in java

    - by Jay
    hi guys i am just doing some reading for myself to learn java and came across this problem and is currently stuck. i need to print out series of number based on the input given by the user. for example, if input = 5, the output should be as follows @1@22@333@4444@55555 import java.util.*; public class ex5{ public static void main(String[] args){ Scanner kb = new Scanner(System.in); System.out.println("Please type a #: "); int input = kb.nextInt(); for(int i=0;i<input;i++){ if(input==1){ System.out.print("@1"); } if(input==2){ System.out.print("@1@22"); } } } } this doesnt seem to be working because this is the output i get Please type a #: 2 @1@22@1@22 im not sure what to put inside the for loop right now and i dont think i am using the for loop here very well either... any help guys?

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  • Checking lazy loaded properties have been instantiated

    - by PaulG
    In a class which has a lazy loaded property, such as: private Collection<int> someInts; public Collection<int> SomeInts { get { if (this.someInts == null) this.someInts = new Collection<int>(); return this.someInts; } } Is it worth also having a property such as: public bool SomeIntsExist { get { return (this.someInts != null && this.someInts.Count > 0); } } And then using that property.. eg: if (thatClass.SomeIntsExist) { // do something with thatClass.SomeInts collection } or is this premature optimisation. Its certainly easier to roll with something like below, but it will instantiate the collection needlessly: if (thatClass.SomeInts.Count > 0) { // do something with thatClass.SomeInts collection } Is the compiler smart enough to figure things like this out? Is there a better way?

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  • Is there a way to determine the Variance of an Interface / Delegate in C# 4.0?

    - by BFree
    So now that we have generic Covariance and Contravariance on interfaces and delegates in C#, I was just curious if given a Type, you can figure out the covariance/contravariance of its generic arguments. I started trying to write my own implementation, which would look through all of the methods on a given type and see if the return types and or arguments match the types in the generic arguments. The problem is that even if I have this: public interface IFoo<T> { void DoSomething(T item); } using my logic, it LOOKS like it should be contravariant, but since we didn't actually specify: public interface IFoo<in T> { void DoSomething(T item); } (the in parameter) it isn't actually contravariant. Which leads to my question: Is there a way to determine the variance of generic parameters?

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  • DI with disposable objects

    - by sunnychaganty
    Suppose my repository class looks like this: class myRepository : IDisposable{ private DataContext _context; public myRepository(DataContext context){ _context = context; } public void Dispose(){ // to do: implement dispose of DataContext } } now, I am using Unity to control the lifetime of my repository & the data context & configured the lifetimes as: DataContext - singleton myRepository - create a new instance each time Does this mean that I should not be implementing the IDisposable on the repository to clean up the DataContext? Any guidance on such items?

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  • Custom Web Control - ParseChildren & Resource Objects

    - by Raybiez
    I hope someone can help me. I have the following custom server control: [ParseChildren(true)] public class MyControl : WebControl, INamingContainer { [PersistenceMode(PersistenceMode.InnerProperty)] public string MyProperty { get;set; } } It works perfectly with the following mark-up: <acme:MyControl runat="sever"> <MyProperty>Test String</MyProperty> </acme:MyControl> But if I try to localise the property string, I get a parse error: <acme:MyControl runat="sever"> <MyProperty><%=(string)GetLocalResourceObject("MyResourceKey") %></MyProperty> </acme:MyControl> Even if I cast the type, ASP.NET indicates that the property cannot accept controls as children. How should the expression look like if I want to localise it? I can make the property accessible as an attribute of the control's tag, but I prefer the mark-up above, it looks more elegant and clean. Thanks

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  • How to remove multiple instances and just have one instance while multiple function calls in php ?

    - by Rachel
    public function getHelperInstance() { $user = new Helper(); $user->set($result['data']); return $user; } I am calling getHelper() class multiple times and if $user is not empty than am calling getHelperInstance(), now in my case getHelperInstance() always creates a new instance of Helper() class and so every time I call getHelperInstance() function am creating a new instance of Helper() so is there any way where can I can just create one instance of Helper() and use it multiple times instead of creating a new instance everytime. Any suggestions !!! public function getHelper() { $user = array(); if (!empty($user)) { $user = $this->getHelperInstance(); } return $user; }

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  • Empty object check

    - by developer
    Is there a way to know if all the properties in an object are empty. My object represents fields from database and I want to know if a particular record is present or not. NULL doesnt seem to work.

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  • How can I handle multiple views of a data object? Which design pattern is acceptable?

    - by tranquil.byte
    I have a person object. class Person { private $name; ... } I need to be able to change how they are displayed on the front-end ( visitors have control ). They can choose list view, grid view, photo view for example. class PersonDisplay { public function displayList() { // Query database // Output html to display in list mode } public function displayPhoto() { // Query database // Output html to display in photo mode } } Is this an acceptable way to handle the presentation of the items on the front-end or is there a specific design pattern I should be researching to help me with this task? Does anyone have any suggestions or ideas where this could go wrong or if this could potentially make maintenance a nightmare? The Person object was just an example very similiar to what I am using.

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  • javascript inherance? with Private vars and methods too

    - by Totty
    Hy i need to inherent a class from another. Parent has private var "_data" and private method "_test" and public method "add" Now the child have a public method "add", that uses the private method from the parent "_test" and the private var "_data". How do i do this? var Parent = function(){ var _data = {}; var _test = function(){alert('test')}; this.add = function(){alert('add from parent')} } var Child = function(){ this.add = function(){// here uses the _data and _test from the Parent class alert('add from child') } } // something to inherent Child from Parent // instance Child and use the add method And i think im miss the prototype concept (http://stackoverflow.com/questions/892467/javascript-inheritance)

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  • c# Generic overloaded method dispatching ambiguous

    - by sebgod
    Hello, I just hit a situation where a method dispatch was ambiguous and wondered if anyone could explain on what basis the compiler (.NET 4.0.30319) chooses what overload to call interface IfaceA { } interface IfaceB<T> { void Add(IfaceA a); T Add(T t); } class ConcreteA : IfaceA { } class abstract BaseClassB<T> : IfaceB<T> { public virtual T Add(T t) { ... } public virtual void Add(IfaceA a) { ... } } class ConcreteB : BaseClassB<IfaceA> { // does not override one of the relevant methods } void code() { var concreteB = new ConcreteB(); // it will call void Add(IfaceA a) concreteB.Add(new ConcreteA()); } In any case, why does the compiler not warn me or even why does it compile? Thank you very much for any answers.

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  • How can I refactor that code ? (state pattern ?)

    - by alex
    Hello guys, How can I refactor that code ? public enum enum1 { value1 = 0x01, value2 = 0x02, value3 = 0x03, value4 = 0x04, value5 = 0x05, UNKNOWN = 0xFF } class class1 { private const string STR_VALUE1 = "some text description of value1"; private const string STR_VALUE2 = "some text description of value2"; private const string STR_VALUE3 = "some text description of value3"; private const string STR_VALUE4 = "some text description of value4"; private const string STR_VALUE5 = "some text description of value5"; private const string STR_VALUE6 = "some text description of unknown type"; public static string GetStringByTypeCode(enum1 type) { switch(type) { case enum1.value1: return STR_VALUE1; case enum1.value2: return STR_VALUE2; case enum1.value3: return STR_VALUE3; case enum1.value4: return STR_VALUE4; case enum1.value5: return STR_VALUE5; default: return STR_VALUE6; } } } PS: there are many enum1...enumX and GetStringByTypeCode(enum1) ... GetStringByTypeCode(enumX) methods.

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  • Fastest implementation of the frac function in C#

    - by user349937
    I would like to implement a frac function in C# (just like the one in hsl here http://msdn.microsoft.com/en-us/library/bb509603%28VS.85%29.aspx) but since it is for a very processor intensive application i would like the best version possible. I was using something like public float Frac(float value) { return value - (float)Math.Truncate(value); } but I'm having precision problems, for example for 2.6f it's returning in the unit test Expected: 0.600000024f But was: 0.599999905f I know that I can convert to decimal the value and then at the end convert to float to obtain the correct result something like this: public float Frac(float value) { return (float)((decimal)value - Decimal.Truncate((decimal)value)); } But I wonder if there is a better way without resorting to decimals...

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  • Finding a handle that persists when relaunching parent

    - by cidtek
    I need to interact with 3'rd party applications by knowing the handle of certain text fields, but the hWnd always changes when that window is recreated. Is there any method that would allow me to identify a window and repeatedly be able to access that window (even after it is closed and then reopened) without having the user manually identify the window? I need the user to be able to identify a window with the usual click, drag and release method but only have to do it once and not every time the target window is recreated.

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  • How to specify a different column for a @Inheritance JPA annotation

    - by Cue
    @Entity @Inheritance(strategy = InheritanceType.JOINED) public class Foo @Entity @Inheritance(strategy = InheritanceType.JOINED) public class BarFoo extends Foo mysql> desc foo; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | +---------------+-------------+ mysql> desc barfoo; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | | foo_id | int | | bar_id | int | +---------------+-------------+ mysql> desc bar; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | +---------------+-------------+ Is it possible to specify column barfo.foo_id as the joined column? Are you allowed to specify barfoo.id as BarFoo's @Id since you are overriding the getter/seeter of class Foo? I understand the schematics behind this relationship (or at least I think I do) and I'm ok with them. The reason I want an explicit id field for BarFoo is exactly because I want to avoid using a joined key (foo _id, bar _id) when querying for BarFoo(s) or when used in a "stronger" constraint. (as Ruben put it)

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  • WPF: How to bind RadioButtons to an enum?

    - by Sam
    I've got an enum like this: public enum MyLovelyEnum { FirstSelection, TheOtherSelection, YetAnotherOne }; I got a property in my DataContext: public MyLovelyEnum VeryLovelyEnum { get; set; } And I got three RadioButtons in my WPF client. <RadioButton Margin="3">First Selection</RadioButton> <RadioButton Margin="3">The Other Selection</RadioButton> <RadioButton Margin="3">Yet Another one</RadioButton> Now how do I bind the RadioButtons to the property for proper two-way-binding?

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  • DllImport Based on OS Platform

    - by Ngu Soon Hui
    I have a mixture of unmanaged code ( backend) and managed code ( front end), as such, I would need to call the unmanaged code from my managed code, using interop techniques and DllImport attribute. Now, I've compiled two versions of unmanaged code, for both 32 and 64 bit OS; they are named service32.dll and service64.dll respectively. So, in my .Net code, I would have to do a DllImport for both dlls: [DllImport(@"service32.dll")] //for 32 bit OS invocation public static void SimpleFunction(); [DllImport(@"service64.dll")] //for 64 bit OS invocation public static void SimpleFunction(); And call them depending on which platform my application is running on. The issue now is that for every unmanaged function, I have to declared it twice, one for 32 bit OS and one for 64 bit OS. This is a duplication of work, and everytime I change the signature of an unmanaged function, I have to modified it in two places. Is there anyway that I can change the argument in DllImport so that the correct dll will be invoked automagically, depending on the platform?

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  • java - how to split string in to multiple parts?

    - by Ewen
    I have a string that contains a value "firstword second third", and an ArrayList. I want to split the whole string in to by spaces and add the splitted strings in to the ArrayList. For example,"firstword second third" can be split to three separate strings and added three times in to the ArrayList. "1 2 3 4" can be splitted in to 4 strings and added 4 times in to the ArrayList. See the code below: public void separateAndAdd(String notseparated) { for(int i=0;i<canBeSepartedinto(notseparated);i++{ //what should i put here in order to split the string via spaces? thearray.add(separatedstring); } } public int canBeSeparatedinto(String string) //what do i put here to find out the amount of spaces inside the string? return .... } Please leave a comment if you dont get what I mean or I should fix some errors in this post. Thanks for your time!

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  • VBA Access Import Specification strange error

    - by captonssj
    I am trying to import a text file into Access using a saved "Import Specification" in my access database using VBA. The import generates the Import Error table showing the errors in the last two fields. BUT if I use the same import specification manually to import the text file, the Import works perfect !!!!! Strange ..... why would they have different behavior ? Here is the database and the text file http://www.box.net/shared/ro7n3b7a77

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  • functional dependencies vs type families

    - by mhwombat
    I'm developing a framework for running experiments with artificial life, and I'm trying to use type families instead of functional dependencies. Type families seems to be the preferred approach among Haskellers, but I've run into a situation where functional dependencies seem like a better fit. Am I missing a trick? Here's the design using type families. (This code compiles OK.) {-# LANGUAGE TypeFamilies, FlexibleContexts #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u => a -> StateT u IO a -- plus other functions class Universe u where type MyAgent u :: * withAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } defaultWithAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () defaultWithAgent = undefined -- stub -- plus default implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- .. and they'll also need to make SimpleUniverse an instance of Universe -- for their agent type. -- instance Universe SimpleUniverse where type MyAgent SimpleUniverse = Bug withAgent = defaultWithAgent -- boilerplate -- plus similar boilerplate for other functions Is there a way to avoid forcing my users to write those last two lines of boilerplate? Compare with the version using fundeps, below, which seems to make things simpler for my users. (The use of UndecideableInstances may be a red flag.) (This code also compiles OK.) {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u a => a -> StateT u IO a -- plus other functions class Universe u a | u -> a where withAgent :: Agent a => (a -> StateT u IO a) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } instance Universe SimpleUniverse a where withAgent = undefined -- stub -- plus implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- And now my users only have to write stuff like... -- u :: SimpleUniverse u = SimpleUniverse "mydir"

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  • Difference of two series in MySQL

    - by Brian
    I have a table with the following fields in MySQL: date, Value, Type. Type can be either exports or imports. I want a query that returns the trade deficit (exports-imports) for each month. Is this possible with a single query?

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  • Inserting checkbox values

    - by rabeea
    hey i have registration form that has checkboxes along with other fields. i cant insert the selected checkbox values into the data base. i have made one field in the database for storing all checked values. this is the code for checkbox part in the form: Websites, IT and Software Writing and Content <pre><input type="checkbox" name="expertise[]" value="Design and Media"> Design and Media <input type="checkbox" name="expertise[]" value="Data entry and Admin"> Data entry and Admin </pre> <pre><input type="checkbox" name="expertise[]" value="Engineering and Skills"> Engineering and Science <input type="checkbox" name="expertise[]" value="Seles and Marketing"> Sales and Marketing </pre> <pre><input type="checkbox" name="expertise[]" value="Business and Accounting"> Business and Accounting <input type="checkbox" name="expertise[]" value="Others"> Others </pre> and this is the corresponding php code for inserting data $checkusername=mysql_query("SELECT * FROM freelancer WHERE fusername='{$_POST['username']}'"); if (mysql_num_rows($checkusername)==1) { echo "username already exist"; } else { $query = "insert into freelancer(ffname,flname,fgender,femail,fusername,fpwd,fphone,fadd,facc,facc_name,fbank_details,fcity,fcountry,fexpertise,fprofile,fskills,fhourly_rate,fresume) values ('".$_POST['first_name']."','".$_POST['last_name']."','".$_POST['gender']."','".$_POST['email']."','".$_POST['username']."','".$_POST['password']."','".$_POST['phone']."','".$_POST['address']."','".$_POST['acc_num']."','".$_POST['acc_name']."','".$_POST['bank']."','".$_POST['city']."','".$_POST['country']."','".implode(',',$_POST['expertise'])."','".$_POST['profile']."','".$_POST['skills']."','".$_POST['rate']."','".$_POST['resume']."')"; $result = ($query) or die (mysql_error()); this code inserts data for all fields but the checkbox value field remains empty???

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