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  • Communication between c++ objects.

    - by Pradyot
    This is an issue, that I have come acrosss earlier. Basically a c++ object has a member object that does some work, once the work is done , a notification needs to made to the parent. What is the most elegant solution to allow this communication. Does being in this position indicate a flaw with the design to begin with? To elaborate. class A { B member; void do_something(); } class B{ void talk_to_network(); }; void do_something() { //Conditional wait on a variable that will change when talk to network completes. //So need a way for B to inform A, that it is done. }

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  • How can i add column name in list generic?

    - by Phsika
    class MyExcelSheets { public List MyColumnNames { get; set; } } how can i add Excel data's column name in "List MyColumnNames ". it returns to me Object reference not set to an instance of an object. i want to use above class in: myexcelSheet = new MyExcelSheets(); myexcelSheet.MyColumnNames = new MyExcelSheets().MyColumnNames; foreach (DataColumn col in dTable.Columns) myexcelSheet.MyColumnNames.Add(col.ColumnName.ToString()); How can i solve it? Error: NullReferenceException

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  • Showing/Hiding the main form in C#

    - by DazSlayer
    I am working on a program where clicking on a button on form1 will open form2. I will then hide form1 until form2 is closed. The problem I have is that I cannot get form1 to show after form2 closes. Any ideas on how to fix this? try { Form1.ActiveForm.Hide(); AddGradeForm = new Form2(Form.NumberOfSelections); AddGradeForm.ShowDialog(); MessageBox.Show(AddGradeForm.Result.ToString()); } catch (Exception i) { Form1.ActiveForm.Hide(); AddGradeForm.Dispose(); AddGradeForm = new Form2(Form.NumberOfSelections); AddGradeForm.ShowDialog(); MessageBox.Show(AddGradeForm.Result.ToString()); } Form1.ActiveForm.Show(); ERROR: NullReferenceException was unhanded. Object reference not set to an instance of an object.

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  • Why do C# and Java require everything to be in a class?

    - by Javier Badia
    It seemed like this question should have been asked before, but searching found nothing. I've always wondered what's the point of making us put every bit of code inside a class or interface. I seem to remember that there were some advantages to requiring a main() function like C, but nothing for classes. Languages like Python are, in a way, even more object oriented than Java since they don't have primitives, but you can put code wherever you want. Is this some sort of "misinterpretation" of OOP? After all, you can write procedural code like you would in C and put it inside a class, but it won't be object oriented.

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  • Retrieving Gtk::Widget's relative position: get_allocate() doesn't work

    - by a-v
    I need to retrieve the position of a Gtk::Widget relative to its parent, a Gtk::Table. Most sources (e.g. http://library.gnome.org/devel/gtk-faq/stable/x642.html) say that one needs to call Gtk::Widget::get_allocation(). However, the returned Gtk::Allocation object always contains x = -1, y = -1, width = 1, height = 1. I have to note that this happens before the Gtk::Table object is actually exposed and rendered. A call to show_all_children() or check_resize(), which I would expect to recalculate child widget geometry, doesn't help. What am I doing wrong? Thanks in advance.

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  • Choose between multiple options with defined probability

    - by Sijin
    I have a scenario where I need to show a different page to a user for the same url based on a probability distribution, so for e.g. for 3 pages the distribution might be page 1 - 30% of all users page 2 - 50% of all users page 3 - 20% of all users When deciding what page to load for a given user, what technique can I use to ensure that the overall distribution matches the above? I am thinking I need a way to choose an object at "random" from a set X { x1, x2....xn } except that instead of all objects being equally likely the probability of an object being selected is defined beforehand.

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  • Mapping LINQ to SQL table to another very similar table without iterating through every one

    - by Daniel Coffman
    Apologies for the vague question. Here it is: I have a table object created by LINQ to SQL. I am copying entries from one table to an "archive" table that has all the columns of the original, plus a couple extra ones. It feels sloppy to iterate through every object and manually define the mapping like: foreach (oldTable in dbContextOldTables) { var newTable = new NewTable(); newTable.TableID = oldTable.ID; newTable.Title = oldTable.Title; ... (repeat for twenty columns) newTable.ColumnThatIsntInOldTable = "Data that will be the same for every row"; dbContext.NewTables.InsertOnSubmit(newTable); } dbContext.SubmitChanges(); Is there a clever way to do this?

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  • Ruby hash value truthiness and symbols

    - by John Topley
    Could somebody please explain why the variable named foo remains true in the code below, even though it's set to false when the method is called? And why the symbol version behaves as expected? def test(options = {}) foo = options[:foo] || true bar = options[:bar] || :true puts "foo is #{foo}, bar is #{bar}" end >> test(:foo => false, :bar => :false) foo is true, bar is false I've only tried this using Ruby 1.8.7.

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  • The member [class] has no supported translation to SQL

    - by Code Sherpa
    Hi, I am getting the following error: Error Message:The member 'Company.ProductCore.Core.Domain.Account.Email' has no supported translation to SQL. My method looks like this: public Account GetAccountByEmail(string email) { Account account; using (WorkbookDataContext dc = _conn.GetContext()) { account = ( from a in dc.Accounts join em in dc.Emails on a.AccountId equals em.AccountId where a.Email.EmailAddress == email select a).FirstOrDefault(); } return account; } My Account class has a getter / setter that exposes Email: public Email Email { get { return _email; } set { _email = value; } } And my Email is a LINQ object. I have a feeling that the problem is that I am using a LINQ object for me Email property? I am new to LINQ and am not really sure why this is happening. Help appreciated, thanks...

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  • Does F# have an equivalent to Haskell's take?

    - by McMuttons
    In Haskell, there is a function "take n list" which returns the first n elements from a list. For example "sum (take 3 xs)" sums up the first three elements in the list xs. Does F# have an equivalent? I expected it to be one of the List-functions, but I can't spot anything that seems to match.

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  • Javascript Pointers question with Dates

    - by Mega Matt
    I noticed this situation in my code (unfortunately), and was able to duplicate it in my own JS file. So I have this code: var date1 = new Date(); // today var date2 = date1; date2 = date2.setDate(date2.getDate() + 1); // what is date1? After this code executes, date1 is today's date + 1! This harkens back to my undergrad days when I learned about pointers, and I guess I'm a little rusty. Is that what's happening here? Obviously I've moved the assignment away from date1, and am only modifying date2, but date1 is being changed. Why is this the case? Incidentally, after this code executes date2 is a long number like 1272123603911. I assume this is the number of seconds in the date, but shouldn't date2 still be a Date object? setDate() should return a Date object... Thanks for the help.

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  • Why doesn't list.get(0).equals(null) work?

    - by Jessy
    The first index is set to null (empty), but it doesn't print the right output, why? //set the first index as null and the rest as "High" String a []= {null,"High","High","High","High","High"}; //add array to arraylist ArrayList<Object> choice = new ArrayList<Object>(Arrays.asList(a)); for(int i=0; i<choice.size(); i++){ if(i==0){ if(choice.get(0).equals(null)) System.out.println("I am empty"); //it doesn't print this output } }

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  • Binding Enum[] to ListBox

    - by Polaris
    Hello. I have next enumeration Enum rcCategory { Incoming, Internal, Outgoing } and I have property "categories" in my class which has rcCategory[] type. I would like to bind this property to the listBox. I use next code for this MyListBox.SetBinding (ListBox.ItemsSource, new Binding {Source= myClass.categories}); But this code doesnt work as expected. How Can I do this. My listBox always is empty but source property has value

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  • Java LinkedList iterator being exhausted prematurely

    - by Sujeet
    I am using LinkedList and retrieving an Iterator object by using list.iterator(). After that, I am checking it.hasNext(), real issue is while checking it.hasNext(), sometimes it returns false. I need help why this is happening, though I have elements in the list. Some code: public synchronized void check(Object obj) throws Exception { Iterator itr = list.iterator(); while(itr.hasNext()) { //This Line I get false.. though i have list size is 1 Item p = (Item)itr.next(); if(p.getId() == null) {continue;} if(p.getId().getElemntId() == obj.getId() || obj.getId() == 0 ) { p.setResponse(obj); notifyAll(); return; } } Log.Error("validate failed obj.getId="+obj.getId()+" **list.size="+list.size()*This shows 1*); throw new Exception("InvalidData"); }

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  • Haskell lists difference

    - by user559354
    I'm trying make a lists difference. Found directly prelude operator \\\\ that makes lists difference. But errors Not in scope: '\\\\' occurs. Here is my simple from command line interpreter: Prelude> ([1,2,3] ++ [5,6]) -- works like expected [1,2,3,4,5,6] prelude> ([1,2,3] \\\\ [1,2]) -- erros occurs <interactive>:1:11: Not in scope: "\\\\" Thanks for explanation where I make a mistake.

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  • second external javscript file not loaded

    - by YsoL8
    Hi I have these lines in my html head section <script type="text/javascript" src="../behaviour/location.js"></script> <script type="text/javascript" src="../behaviour/ajax.js"></script> When I use either in isolation, the code in the external files executes as expected. However, when I use both, I find that neither works correctly. What do I need to do to fix this?

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  • Gridview SortExpression with 2 fields

    - by aron
    Hello, I have a GridView that get's its datasource from a complex object. So I'm doing the Sorting & Paging in the code behind. <asp:GridView ID="SystemsDetailList" runat="server" AllowSorting="true" AllowPaging="true" AutoGenerateColumns="False" ShowFooter="True" OnPageIndexChanging="gridView_PageIndexChanging" OnSorting="gridView_Sorting"> For an important title column I have a SortExpression with 2 fields: SortExpression="FunctionalAreaDisplayCode, EswbsDisplayCode" This in the code behind: protected void gridView_Sorting(object sender, GridViewSortEventArgs e) { BindSystemList(e.SortExpression, sortOrder); } public string sortOrder { get { if (ViewState["sortOrder"].ToString() == "desc") { ViewState["sortOrder"] = "asc"; } else { ViewState["sortOrder"] = "desc"; } return ViewState["sortOrder"].ToString(); } set { ViewState["sortOrder"] = value; } } For some reason it will keep "FunctionalAreaDisplayCode" always sorted ASC but the EswbsDisplayCode works fine as it flips between ASC and DESC correctly. and tips here? thanks!

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  • Convert sets to frozensets as values of a dictionary

    - by Space_C0wb0y
    I have dictionary that is built as part of the initialization of my object. I know that it will not change during the lifetime of the object. The dictionary maps keys to sets. I want to convert all the values from sets to frozensets, to make sure they do not get changed. Currently I do that like this: for key in self.my_dict.iterkeys(): self.my_dict[key] = frozenset(self.my_dict[key]) Is there a simpler way to achieve this? I cannot build frozenset right away, because I do not how much items will be in each set until i have built the complete dictionary.

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  • C#, Using Custom Generic Collection faster with objects than List

    - by Kaminari
    Hello, I'm using for now List< to iterate through some object collection and find matching element, The problem is that object has only 2 significant values Name and Link (strings) but has some other values wich I dont want to compare. I'm thinkig about using something like HashSet (wich is exactly what I'm searching for - fast) from .NET 3.5 but target framework has to be 2.0. There is something called Power Collections here: http://powercollections.codeplex.com/ But maybe there is other way? If not, can you suggest me a suitable custom collection?

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  • how can I pass method Of one class to another class ?

    - by srikanth rongali
    I have a ClassA. in ClassA there is a method(-(void)parseData:). I have a ClassB which have ClassA object. And ClassB *aClassB is member variable of ClassA. In ClassB the code is aClassB = [[ClassB alloc]init]; [aClassB parseData]; I have ClassC. I need to use the method parseData of ClassB in ClassC. I think I can use the object created in ClassB of ClassA. How can I pass the method to ClassC ? Thank You.

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  • How listview delete data in database

    - by Bud33
    I have a problem to delete data in listview, I was able to delete data in listview select record, but data which selected is not deleted in the database, I have a source code Private _updateinputalltrans As Boolean Private Sub btndelete_Click(sender As System.Object, e As System.EventArgs) Handles btndelete.Click With Me.listviewpos.SelectedItem .Remove() End With MessageBox.Show("Are you sure delete this record?", "Confirmation", MessageBoxButtons.YesNo, MessageBoxIcon.Exclamation, New EventHandler(AddressOf DeleteData)) End Sub Private Sub DeleteData(ByVal sender As Object, ByVal e As EventArgs) Dim conn As New Connection(Connectiondb) If Me.updateinputalltrans = False Then If Me.listviewpos.Items.Count > 0 Then For Each del As ListViewItem In listviewpos.Items conn.delete_dtpospart(del.Text) Next End If End If End Sub delete_dtpospart a declare which connection to the database using a stored procedure

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  • Why can't I make my parameter like this?

    - by mystify
    - (void)setPropertyValue:(const *void)inValue forID:(UInt32)propertyID { } The compiler doesn't like the const *void, for some reason. When I have that, it says: error: expected ')' before 'void' When I make the parameter like (UInt32)foo there is no problem. Does const *void only work in functions? I need a parameter which can be a "pointer to anything" like UInt32, Float64, etc.

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  • Single C++/CLI method to wrap many type specific C functions

    - by T33C
    I am wrapping a C library using C++/CLI so that the C library can be used easily from C# in a C#'ish way. Some of the functions in this library are for putting a value into a container. There are no generics in C so there exists a function per type CLIB_SetBool(BOOL value), CLIB_SetInt(int value), CLIB_SetString(char* string) and so on. To make it easier to use from C#, I have created a single Set function which takes a System::Object. I have two related questions: With my method how would you use a switch statement on the type of System::Object to call the correct CLIB_Setxxxx function. [typeid is only for unmanaged code and I can't seem to use GetType.] Is there a better way to wrap these functions like using a Generic? [I started using template specialisation but then realised that C# doesn't see templates.] Thanks.

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  • c++ class in cocoa

    - by joels
    Any ideas why Xcode wont let me define a c++ class in my cocoa project? I am trying to use a C++ class in my cocoa project but I am getting build errors just creating the c++ header file. class SomeClass{ public: int count; } Expected '=', ',', ';', 'asm' or 'attribute' before 'SomeClass' in ..... If I remove all code from the header file, ?the cpp file builds without any errors and is included in the list of compiled sources...

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  • A generic list of generics

    - by SnOrfus
    I'm trying to store a list of generic objects in a generic list, but I'm having difficulty declaring it. My object looks like: public class Field<T> { public string Name { get; set; } public string Description { get; set; } public T Value { get; set; } /* ... */ } I'd like to create a list of these. My problem is that each object in the list can have a separate type, so that the populated list could contain something like this: { Field<DateTime>, Field<int>, Field<double>, Field<DateTime> } So how do I declare that? List<Field<?>> (I'd like to stay as typesafe as possible, so I don't want to use an ArrayList).

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