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Hey, everyone. I ran into a little puzzler this morning that took me back to my early days of OOP, and I'd appreciate it if someone could point out what I'm failing to understand.
I was attempting to check the values of two System::Drawing::Point objects for equality, and the equality operator did not behave as I expected. Now, before you jump all over me about it, I do understand the difference between using the virtual method Object::Equals() and the equality operator '==' on two handles. Well, at least, I thought I did until I decided I might just be crazy a few minutes ago.
I know that operator== will only check to see if two handles refer to the same instance unless it is overridden to do value checking instead, but it is overridden for the Point class. MSDN reports that System::Drawing::Point::operator==() "compares two Point objects. The result specifies whether the values of the X and Y properties of the two Point objects are equal."
My silly little test case (in C++/CLI) follows:
Point^ p1 = gcnew Point(0, 0);
Point^ p2 = gcnew Point(0, 0);
label1->Text = (p1 == p2).ToString();
label2->Text = (p1->Equals(p2)).ToString();
Label1 reads "false" and label2 reads "true," which is the behavior I would expect if the Point class didn't override operator==, but it appears to. I've Googled around and searched through a few forums, but haven't found anyone complaining of the same issue.
I know this just has to be some silly little error that I'm making, either in implementation or understanding, and I'm going to be embarrassed when someone smacks me with the clue bat. I'd much rather understand and be embarrassed than continue to misunderstand, though.
Thanks, gang, and try to be gentle. 
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With my minimal C++ knowledge, the code you supplied is working how it is suppose to (in C++). I could understand if MSDN was making reference to the VB or VC# aspects of the == operator. If you are sure the MSDN article was for C++, then the only thing I can say is "Microsoft is only perfect" (try not to laugh to hard at the statement). Microsoft and its employees could have been mistaken in that aspect (wouldn't be the first time).
Regards,
Thomas Stockwell
Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.
Visit my homepage Oracle Studios[ ^]
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I went digging around MSDN again to give you a link to what I was looking at when I figured out where I was being a doofus. 
System.Drawing.Point is a value class. When I did Point^ p1 = gcnew Point(0, 0);, a new Point value was created, then immediately boxed so the handle p1 could refer to it. p1 == p2 was then operating on Point handles, not Point values.
Here's another little snippet:
Point p1 = Point(0, 0);
Point p2 = Point(0, 0);
Point^ hp1 = p1;
Point^ hp2 = p2;
this->label1->Text = (p1 == p2).ToString();
this->label2->Text = (hp1 == hp2).ToString();
I really should have known that, I mean, it's pretty basic stuff. I do feel better now that I figured it out, though. Sorry for the board, clutter, gang!
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Hello all. I am in dire need of some help. I have a project that I need to complete STAT! Here is the rundown:
I have a form. This form has six controls on it. They do nothing.
I have another form that retrieves these these control in a Control[] array.
On this second form, there is a comboBox and a richTextBox.
The comboBox is populated with the names of the controls.
I have absolutely no problem getting the names of the properties; I can get them fine.
I cannot get the value of each of these properties. I know that there is a GetValue(object, object[] index) method that is supposed to return the value of a property, but I can not get it to work to save my life!
I have included the code from the SelectedIndexChanged event of the combobox, and the class that represents a property below. Assume that the rest of the program works because it does.
If the GetValue call is dropped off the end of the last line below, all of the properites' names are properly listed in the textBox.
Please show me how I should call this method. Any sugestions would be greatly appreciated!
private void myCboBox_SelectedIndexChanged(object sender, EventArgs e)
{
//creates an int to hold the selected index:
int index = myCboBox.SelectedIndex;
//creates a type variable:
Type t = controls[index].GetType();
MyProperty Myproperty = new MyProperty(t.Name, null);
PropertyInfo[] myProps = t.GetProperties();
foreach (PropertyInfo p in myProps)
{
richTextBox1.Text += "\n" +
//The GetValue call is whats killing me!
//Throws a TargetException
//Going crazy here! Please help!
p.Name + "\t\t\t\t" +p.GetValue((object)Myproperty, null);
}
}
}
public class MyProperty
{
public MyProperty(string aName, object aValue)
{
theName = aName;
theValue = aValue;
}
private static string theName;
public static string theNameProp
{
get { return theName; }
set { theName = value; }
}
private static object theValue;
public static object intTest2
{
get { return theValue; }
set { theValue = value; }
}
}
"If you don't know where you're going, you'll probably end up somewhere else." Yogi Berra
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In your foreach loop:
1) p is a PropertyInfo of Type t
2) you call p.GetValue with an instance of type MyProperty, which is probably not of type t
Therefore the exception.
You should call GetProperty with the instance from the controls collection, where you get the type from.
regards
Urs
-^-^-^-^-^-^-^-
no risk no funk
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Try p.GetValue(Myproperty, null) instead of p.GetValue((object)Myproperty, null). The is no need to cast Myproperty to an object since its already an object.
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I have an application which is converted from VC6 to VC7.1 (.net 2003)
I'm trying to debug in .net 2003 i need to check the return value HRESULT value. I have declared hr as
HRESULT hr = S_OK;
When i add "hr" in watch window it displays a message CXX0017: Error: symbol "hr" not found
When i try to set the cursor on HRESULT hr = S_OK line (using Set Next Statement) it does not execute that line.
Could you please let me know what could be the reason? and why cant i see the hr value.
Thanks
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You're really in the wrong forum. You should generally ask C++ questions in the Visual C++/MFC forum[^]. This forum (.NET Framework) is for general managed code, e.g. Visual Basic or C#, non-language-specific questions.
That said, most likely you're trying to debug a release build. The optimizer has most likely optimized away the hr variable, leaving its value only in a variable. Or, if you're never writing to it, just replacing it everywhere it's used with the static value 0 (which is the value of S_OK).
Always debug a non-optimized, debug build of your application to begin with. It's important to test release builds but I'd generally only load one into the debugger if there's a problem that doesn't reproduce in the debug build.
DoEvents: Generating unexpected recursion since 1991
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Hello,
I am new to .net framework. Previusoly i was working in VC++. When i see the applications in .net, all code is in ".h" file not in ".cpp" file.
Why this, i am confusing about this.
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In C# (and VB.net as far as I know) you do not have seperate header and implementation files. You have only one (e.g. .cs on C#) for normal code. This file contains for example the class with its interface and implementation in one place.
There can exist several files when classes are marked partial (normally used for classes that are partly auto-generated).
regards
Urs
-^-^-^-^-^-^-^-
no risk no funk
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I need a text editor with the ability of editing .RTF files (if not word files) . Something like TE Edit Control.(You can find it in http://www.subsystems.com site). But I want it to be free or have its crack ) I really need this for a project.
Best Regards , Hossein
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devboycpp wrote: have its crack
So, you're a thief and you're hoping we will help you ?
Christian Graus
Please read this if you don't understand the answer I've given you
"also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )
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devboycpp wrote: have its crack
If you are going to use this in your project, let me know of your organization name and project manager so that I can report them to Intellectual Property Rights organization of your country.
Vasudevan Deepak Kumar
Personal Homepage
Tech Gossips
A pessimist sees only the dark side of the clouds, and mopes; a philosopher sees both sides, and shrugs; an optimist doesn't see the clouds at all - he's walking on them. --Leonard Louis Levinson
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Since I do actually help people on the odd occasion....
Google
EditPad Lite
-= Reelix =-
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This seems so silly, but,
I've been googling now for 2 hours and can't find an answer. Hope someone here can help.
I create a temp directory on the path Environment.SpecialFolder.LocalApplicationData combined with a session guid. No problem - the directory is created. The problem is that the 'Use folder type as a template:' (Explorer directory-properties-customize) is set by default on the create to 'Pictures and Videos' or 'Music' and I was wanting it to be set to 'All items'. (The folder look is incorrect on Process (verb 'open') explorer load.)
Any help for the call to change the folder type would be greatly appreciated. (I'm running on Vista with VS2005).
Thanks.
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Strange Behavior with Generics:
When I define a Generic at class level with a constraint, I get a compile exception , however , when I implement Generic at method level with the same constraint , all goes well ...
Wondering , wether its a bug in generics or the bug lies in my way of interpretation 
Have Tried to explain the problem below :
Case 1:
I have defined a abstract generic class and defined the generic type at class level , with a constraint . Below is the class definition.
public abstract class BaseVOMapper<T> where T:BaseVO
{
public abstract void Insert(BaseVO child , BaseVO parent );
public abstract void SaveChildrens(List<T> childListToPersist, BaseVO parentVO);
}
Below is the implementation o f the derived class , where FlightList is a List<FlightVO> & FlightVO: BaseVO & as per polymorphism ,I assume , I can pass List<FlightVO> where List<BaseVO> is expected.However , I endup getting the below error.
Argument '1': cannot convert from 'System.Collections.Generic.List<ValueObjects.FlightVO>' to 'System.Collections.Generic.List<ValueObjects.BaseVO>'
i.e
public class FlightVO : BaseVO
{
public int FlightId;
public string FlightName;
}
public class ScheduleVOMapper: BaseVOMapper<BaseVO>
{
public override void Insert(ValueObjects.BaseVO child, ValueObjects.BaseVO parent)
{
//((ScheduleVO)child).FlightList
this.SaveChildrens(((ScheduleVO)child).FlightList, parent);
}
public override void SaveChildrens(List<BaseVO> childListToPersist, BaseVO parentVO)
{
foreach (BaseVO child in childListToPersist)
{
ORlayerEngine.Persist(child, parentVO);
}
}
}
------------------------------------------------------------------Code using Generic at Method Level ------------------------------------------------------------------------------------------
Case 2
// generic type specified at method level , with the same constraint
public abstract class BaseVOMapper
{
public abstract void Insert(BaseVO child , BaseVO parent );
public abstract void SaveChildrens<T>(List<T> childListToPersist, BaseVO parentVO) where T:BaseVO ;
}
Below is the implementation of the derived class :
public class ScheduleVOMapper: BaseVOMapper
{
public override void Insert(ValueObjects.BaseVO child, ValueObjects.BaseVO parent)
{
//((ScheduleVO)child).FlightList
this.SaveChildrens(((ScheduleVO)child).FlightList, parent);
}
public override void SaveChildrens<T>(List<T> childListToPersist, BaseVO parentVO)
{
foreach (BaseVO child in childListToPersist)
{
ORlayerEngine.Persist(child, parentVO);
}
}
}
Comparing Case 1 & Case 2 , in case 1 , in the derived class ScheduleVOMapper , the SaveChildrens method has the generic type explicity specified as BaseVO ,
whereas in Case 2 , the method gets the Generic Type at runtime , which anyways as per the constraint has to be of Type BaseVO.
Though , I have my solution implemneted using Case 2 , would really like to get my doubt's cleared
Many Thanks
Girija
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Why do you declare
girijaa wrote: public class ScheduleVOMapper: BaseVOMapper<basevo>
and not FlightVO instead of BaseVO as generic parameter?
I couldn't test it right now, just guessing.
Urs
-^-^-^-^-^-^-^-
no risk no funk
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We’re struggling to register an unsafe assembly on a development server. The message given is:
CREATE ASSEMBLY for assembly 'Pastel.Evolution' failed because assembly 'Pastel.Evolution' is not authorized for PERMISSION_SET
Now I remember running a grant, “USE Master GRANT EXTERNAL ACCESS ASSEMBLY TO [SERVERNAME\User]” on my server, but the target server doesn’t use windows auth, and you can’t grant rights to ‘sa’. Any ideas on how we can allow ourselves to register an unsafe assmemly?
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I need a help about this.
I've made a program to import csv files. Sometimes I caught this error message "must be less than or equal to max (-1)", I've been search at google and I found some messages saying about DataTable.Select(), something about that.
But I don't know why this error happens, if is the number of parameters or lenght of my csv files. The really problem is that error never happens at development time.
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We have a website set up on our local computer for testing purposes and we then roll out the changes to our main server which is remotely accessed. I want to keep the two databases in sync by calling the dataadapter.update method twice passing in the same datatables (I happen to be using a typed dataset) and just changing the connection string for the remote database (I first wipe each database before the update). However, when I try to do this, after the local site database properly updates and I then call the update method again with a new connection string, the update does not work (it doesn't error, it just isn't working properly) and returns an integer value of 0 telling me that no new rows were updated (if I check the database I see nothing was written in.) I am trying to figure out what the issue is. I am guessing it has something do with the row.rowstate on the rows in the datatable telling the update method that these rows have already been written to the database, but if that is the case, is there any easy way to reset the rows so that update can be called again (I tried fooling with the row.setrowmodified but it didn't work and it gave me a concurrency exception)? For now, the workaround I am using is it to create a new dataset before any update is called, go through every row in the first dataset and write them to each table in the new dataset, and then call the update method passing in the tables of the new dataset. This does work, however it slows the program down considerably when building the new dataset. Anyone have any other ideas or suggestions?
modified on Wednesday, April 30, 2008 9:24 AM
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Is it possible to force a TextBox to show it's input cursor even though it's not active?
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Why would you like to do that?
Could you provide the exact requirement?
Regards,
Dave
Dave Traister
Software Engineer
ComponentOne LLC
www.ComponentOne.com
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If I have a Select statement such as-
[ItemCost]*[ItemQuanity] as ItemSubtotal
How do I name the ItemSubtotal column in another select statement so I can-
[ItemSubtotal]-[AmountPaid] as BalanceDue
When I try this it does not know the ItemSubtotal as a valid column name since I created it in a as column name.
Thanks for the help......
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You can't refer to columns by their alias until the ORDER BY clause because they haven't been serialized as the alias until then. So you have to define your two columns as:
SELECT (ItemCost * ItemQuantity) AS ItemSubtotal,
(ItemCost * ItemQuantity) - AmountPaid AS BalanceDue
If you're using SQL 2005, you could write a user defined function, call it subtotal and then use CROSS APPLY like this:
SELECT S.Subtotal AS ItemSubtotal,
S.Subtotal - ItemQuantity AS BalanceDue
FROM OrderDetails
CROSS APPLY dbo.GetSubTotal(ItemCost, ItemQuantity) S
But if your query isn't returning a large number of rows I really wouldn't worry about it and I would use the first method.
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Mark,
Thanks for the help!
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