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  • Pointer reference and dereference

    - by ZhekakehZ
    I have the following code: #include <iostream> char ch[] = "abcd"; int main() { std::cout << (long)(int*)(ch+0) << ' ' << (long)(int*)(ch+1) << ' ' << (long)(int*)(ch+2) << ' ' << (long)(int*)(ch+3) << std::endl; std::cout << *(int*)(ch+0) << ' ' << *(int*)(ch+1) << ' ' << *(int*)(ch+2) << ' ' << *(int*)(ch+3) << std::endl; std::cout << int('abcd') << ' ' << int('bcd') << ' ' << int('cd') << ' ' << int('d') << std::endl; } My question is why the pointer of 'd' is 100 ? I think it should be: int('d') << 24; //plus some trash on stack after ch And the question is why the second and the third line of the stdout are different ? 6295640 6295641 6295642 6295643 1684234849 6579042 25699 100 1633837924 6447972 25444 100 Thanks.

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  • Acessing a struct member, using a pointer to a vector of structs. Error:base operand of '->' has non-pointer type

    - by Matt Munson
    #include <iostream> #include <vector> using namespace std; struct s_Astruct { vector <int> z; }; int main () { vector <s_Astruct> v_a; for(int q=0;q<10;q++) { v_a.push_back(s_Astruct()); for(int w =0;w<5;w++) v_a[q].z.push_back(8); } vector <s_Astruct> * p_v_a = & v_a; cout << p_v_a[0]->z[4]; //error: base operand of '->' has non-pointer type //'__gnu_debug_def::vector<s_Astruct, std::allocator<s_Astruct> >' } There seems to be some issue with this sort of operation that I don't understand. In the code that I'm working on I actually have things like p_class-vector[]-vector[]-int; and I'm getting a similar error.

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  • Virtual functions - base class pointer

    - by user980411
    I understood why a base class pointer is made to point to a derived class object. But, I fail to understand why we need to assign to it, a base class object, when it is a base class object by itself. Can anyone please explain that? #include <iostream> using namespace std; class base { public: virtual void vfunc() { cout << "This is base's vfunc().\n"; } }; class derived1 : public base { public: void vfunc() { cout << "This is derived1's vfunc().\n"; } }; int main() { base *p, b; derived1 d1; // point to base p = &b; p->vfunc(); // access base's vfunc() // point to derived1 p = &d1; p->vfunc(); // access derived1's vfunc() return 0; }

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  • C# - null vs "Could not evaluate expression"

    - by Vaccano
    I have code like this: private Box mCurBox; public Box CurBox { get { return mCurBox; } set { if (mCurBox != value) { mCurBox = value; } } } When mCurBox is null then CurBox the debugger says "Could not be evaluated". If it knows that the value underneath is null then how come it can't figure it out?

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  • Sharepoint DateTimeControl: set it to null

    - by pistacchio
    Hi, how can I set the selected value of a Sharepoint DateTimeControl to null? When you first load it into a page, there's no value selected (even if the returned value is not properly null but one can check it with IsDateEmpty). How can i programmatically set it back to the initial, empty value? Thanks

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  • LINQ query - null date

    - by d daly
    Hi Ive a simple linq query to return records with a null date field, just want to check the synatx of the "where" line is ok var query2 = from cs in db.tblCases where cs.date_closed == null etc, etc, thanks again DD

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  • getLine1Number return null but not always....

    - by bob
    i use telephony manager for to ger the phone number, in sdk all work perfectly, on some device like my hero with 1.5 it return null, on the tattoo with 1.6 it work but on some other tattoo it return null.....I start to be crazy....why happen this? There is another way for to get the phone number? Thanks

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  • MessageQueue.BeginReceive() null ref error - c#

    - by ltech
    Have a windows service that listens to a msmq. In the OnStart method is have this protected override void OnStart(string[] args) { try { _queue = new MessageQueue(_qPath);//this part works as i had logging before and afer this call //Add MSMQ Event _queue.ReceiveCompleted += new ReceiveCompletedEventHandler(queue_ReceiveCompleted);//this part works as i had logging before and afer this call _queue.BeginReceive();//This is where it is failing - get a null reference exception ; } catch(Exception ex) { EventLogger.LogEvent(EventSource, EventLogType, "OnStart" + _lineFeed + ex.InnerException.ToString() + _lineFeed + ex.Message.ToString()); } } where private MessageQueue _queue = null;

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  • Valid URL-string as NSUrl becomes null

    - by Mike
    Hello, another issue where I seem to have found an solution for ObjC but not MonoTouch. I want a NSUrl from an URL (as string). The string may contain whitespace and backslashes. Why is NSUrl returning null for such string, even though these are valid urls in a browser? For example: NSUrl foo = NSUrl.FromString(@"http://google.com/search?\query"); foo == null Any suggestions?

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  • WinForms: Why is Control.Parent null?

    - by Neil Barnwell
    I'm trying to get the parent of a listview docked within a splitcontainer, and am finding that ListView.Parent is null. According to the documentation this should be: A Control that represents the parent or container control of the control. Can anyone explain why this property would be null? I've tried moving the ListView to the Form (in order to rule out weird behaviour when docked in a splitcontainer) to no avail.

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  • claimsResponse Always Return Null

    - by Chirag Pandya
    Please Help me in this problem. I am getting ClaimsResponse Always Null. I am Seaching lots example for dotnetOpenAuth and also implement in local but it always return null. please send me detail why this happen?? i am using DotNetOpenAuth-3.2.0.9177 in asp.net. i want Email,FullName,Country from ClaimsResponse but i am not able to get it.

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  • Strange, regex.split Method matches one null element

    - by dontoo
    Regex rx = new Regex(@"[+-]"); string[] substrings = rx.Split(expression); expression = "-9a3dcbh-3bca-4ab4cf-3hc" //This is the iput string I want to split that string between + or -. My VS debugger shows substring array like this: substrings[0] = null //???Why substrings[1] = 9a3dcbh substrings[2] = 3bca substrings[3] = 4ab4cf substrings[4] = 3hc Why is the first element of arry null, is it because I am matching +-, and there is no + in my input string?

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  • Why doesn't the conditional operator correctly allow the use of "null" for assignment to nullable ty

    - by Daniel Coffman
    This will not compile, stating "Type of conditional expression cannot be determined because there is no implicit conversion between 'System.DateTime' and ''" task.ActualEndDate = TextBoxActualEndDate.Text != "" ? DateTime.Parse(TextBoxActualEndDate.Text) : null; This works just fine if (TextBoxActualEndDate.Text != "") task.ActualEndDate = DateTime.Parse(TextBoxActualEndDate.Text); else task.ActualEndDate = null;

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  • OperationContext.Current is null and all other contexts too

    - by HeavyWave
    I have a WCF service defined as following: [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] [ServiceBehavior(IncludeExceptionDetailInFaults = true, InstanceContextMode = InstanceContextMode.PerCall)] public partial class FrontEndService : IFrontEndService However, most of the time (but not always -_-) InstanceContext.Current is null, as well as HttpContext.Current and OperationContext.Current is also null. What am I missing? What I want to do is store some data in HttpContext.Current.Items or a similar collection that exists for the length of the request.

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  • Check on null reference

    - by Neir0
    Hello, i have the follow code: searchResults.SearchResultCollection.Add( new SearchResult() { Header = HttpUtility.HtmlDecode( htmlDocument.DocumentNode .SelectSingleNode(initialXPath + "h3") .InnerText), Link = HttpUtility.HtmlDecode( htmlDocument.DocumentNode .SelectSingleNode(initialXPath + "div/cite") .InnerText) } ); Sometimes htmlDocument.DocumentNode.SelectSingleNode(....) returns null and my application crashed with NullReferenceException. Ofcourse i can write code which check returned value on null reference but then code will be overly verbose. What is graceful way to do that?

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  • ASP.NET MVC null ViewResult

    - by David Neale
    How should one deal with an MVC controller returning a null ViewResult? As an example I am creating a simple edit view: public ActionResult Edit(int id) { var person = (from p in context.SWLiftShare_Persons where p.id == id select p).SingleOrDefault(); if (person != null) { return View(person); } else return View(); } I guess in reality there's no point in checking for a null result in the controller because the view picks out properties from the model: <h2>Edit - <%= Html.Encode(Model.Name) %></h2> <%= Html.ValidationSummary("Edit was unsuccessful. Please correct the errors and try again.") %> <% using (Html.BeginForm()) {%> <fieldset> <legend>Fields</legend> <p> <label for="id">id: <%= Html.Encode(Model.id) %></label> </p> <p> <label for="CollarNumber">CollarNumber:</label> <%= Html.TextBox("CollarNumber", Model.CollarNumber)%> <%= Html.ValidationMessage("CollarNumber", "*") %> </p> <p> <label for="Name">Name:</label> <%= Html.TextBox("Name", Model.Name)%> <%= Html.ValidationMessage("Name", "*") %> </p> <p> <label for="EmailAddress">EmailAddress:</label> <%= Html.TextBox("EmailAddress", Model.EmailAddress, new { style = "width:300px" })%> <%= Html.ValidationMessage("EmailAddress", "*") %> </p> <p> <input type="submit" value="Save" /> </p> </fieldset> <% } %> I could just wrap everything in a <% if(Model != null) { //render edit markup... etc. but that seems rather unelegant. Is there a better way to deal with this?

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  • Using GQL to check if BlobProperty is NULL

    - by Joel
    Hello, I have a db.BlobProperty property (called "Icon") in my entity which contains an image binary. I want to run a GQL query to retrieve all entities with an image (i.e. their "Icon" property is not NULL). Trying to use the following query: "SELECT * FROM Names WHERE Icon!=NULL" did not work... Trying to use .filter("Icon!=",None) did not work as well... Any ideas? Thanks! Joel

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  • Defaults for null values

    - by OldFart
    Working on a Powershell script I had several places where I wanted A unless it was null, else B. Essentially the ?? operator in C#. I ended up writing the function shown below, but I can't help but think there is a built-in way to do this. Is there a better, built-in, way? function Get-ValueOrDefault() { foreach ($value in $args) { if ($value -ne $null) { return $value } } } I think this works better: function Get-ValueOrDefault() { $args | select -first 1 }

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  • Are Maybes a good pattern for scala?

    - by Fred Haslam
    For a while I have been struggling to integrate scala with java methods that might return null. I came up with the following utility which helps a lot: // produce an Option, nulls become None object Maybe { def apply[T](t:T) = if (t==null) None else Some(t) } Maybe(javaClass.getResultCouldBeNull()).map( result => doSomeWork(result) ) I have a few questions about this solution: Is there a better or more standard pattern to use? Am I duplicating something that already exists? Does this functionality have hidden gotchas?

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  • Check if DataRow exists by column name in c#?

    - by waqasahmed
    I want to do something like this: private User PopulateUsersList(DataRow row) { Users user = new Users(); user.Id = int.Parse(row["US_ID"].ToString()); if (row["US_OTHERFRIEND"] != null) { user.OtherFriend = row["US_OTHERFRIEND"].ToString(); } return user; } However, I get an error saying US_OTHERFRIEND does not belong to the table. I want to simply check if it is not null, then set the value. Isn't there a way to do this?

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