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hi,
I have a mainform(singleton)and a sub class which does a time related job and needs to show a messagebox at the end of the job. That's where the problem is. The mbox is shown but as soon as I click to OK button on mbox, program gives an exception. I changed my code in different ways but same result.
thanks in advance
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Dunno. What Exception? Have you run it in the debugger?
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yes I ran it in the Debugger and it says "Couldn't find the instance of the object" and goes to the line below in Program.cs file
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(MainForm.Instance); //this is the line
}
Note: when I remove the code for showing messagebox, everything is okay
modified on Wednesday, October 7, 2009 1:52 PM
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Where is MainForm defined? Is it the encapsulating class? Is Instance a static field? Is Instance instantiated? Any of these could be a problem. If MainForm is the encapsulating class, and this is all the code, then I would say, you need to add
MainForm.Instance = new <typename>();
Good luck.
In Christ,
Aaron Laws
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as a newbee,I'll try to answer.
mainform isn't defined somewhere,I made mainform a static singleton and all other classes access mainform members through its instance by saying: MainForm.Instance.xxxxx
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Set a breakpoint where you show the MessageBox and step from there.
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I have a form: when the user fills a form, the application takes this information and creates a data file (.csv) and put it (data file) on the server in a directory (name of this directory is [information]) where the web site is located.
using (System.IO.StreamWriter SW = new System.IO.StreamWriter(Server.MapPath("save/information/Data_" + strDate + ".csv")))
{
SW.WriteLine(s.FirstName + ";" + s.LastName + ";" + s.Address1 + ";");
SW.Close();
}
After, I changed the path for save the file, in a different server than the Web server
StreamWriter SW = new StreamWriter(@"\\111.222.1.00\c$\Inetpub\wwwroot\site_toto\ save\information\Data_" + strDate + ".csv");
It must disable the firewall on server so that it works. I can’t it.
So instead of filing the file with system Windows, I'd like to put with FTP protocole on another place, but I do not know how I can do.
I have a class! How can I integrate it?
Is that correct if I do like that ? :
using (FTP ftplib = new FTP(MapPath ("Data_" + strDate + ".csv")));
try
{
ftplib.Connect("ftp.toto.com",
"tata",
"pata");
ftplib.ChangeDir("information/");
}
catch(Exception ex)
{
Console.WriteLine(s.FirstName + ";" + s.LastName + ";" + s.Address1 + ";");
}
try
{
int perc = 0;
ftplib.OpenDownload("Data_" + strDate + ".csv", true);
while(ftplib.DoDownload() > 0)
{
perc = (int)((ftplib.BytesTotal * 100) / ftplib.FileSize);
Console.Write("\rDownloading: {0}/{1} {2}%",
ftplib.BytesTotal, ftplib.FileSize, perc);
Console.Out.Flush();
}
Console.WriteLine("");
}
catch(Exception ex)
{
Console.WriteLine("");
Console.WriteLine(ex.Message);
}
What do you think of my integration code that you see above? is that this can work or I'm completely wrong
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Dear Sirs,
I just came across some code and changed it. I'm implementing the java Gridbag layout manager to a panel in C#, and in the Insets.Equals(object) code, the following could be found:
if (obj instanceof Insets) {
Insets insets = (Insets)obj;
return ((top == insets.top) && (left == insets.left) &&
(bottom == insets.bottom) && (right == insets.right));
}
return false;
So I sharpified it:
if (obj is Insets)
{
Insets insets = obj as Insets;
return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
}
return false;
Then, almost compulsively, I modified it thus:
Insets insets = obj as Insets;
if (ReferenceEquals(insets, null)) return false;
return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
I do this kind of thing ALL the time. I would like some comments on readability and efficiency.
I guess to characterize the modification, I would say that I make it read more sequentially, without having to skip code (casting your eyes over code because in certain cases it would not be executed). Also, I'm crazy about conserving lines. I suppose that's because I'm not paid per line  . I always use the same-line `if' if I can, and if not, I resort to the no-brace 'if'. Which sometimes means...oh yeah, let me show a line I wrote the other day. Here's what I first wrote:
foreach (Point a in _gr_pts)
{
if (prev == Point.Empty || prev == a)
{
prev = a;
continue;
}
g.DrawArc(_ap_pen, prev, a);
prev = a;
}
Then, I changed it to:
foreach (Point a in _gr_pts)
{
if (prev == Point.Empty || prev == a)
{
prev =a;
continue;
}
g.DrawLine(_ap_pen, prev, prev = a);
}
I tried for a while to figure out how to get the braces out of the if statement...oh yeah, I just realized that this is possible:
(I'm writing free-hand, so there may be typos...)
foreach (Point a in _gr_pts)
if (prev == Point.Empty || prev == a)
{
prev = a;
continue;
}
else g.DrawLine(_ap_pen, prev, prev = a);
I know some people swear by ALWAYS using braces in if, else, do, while, for, foreach statements, (and if I remember correctly, Visual studio has some option about including those compulsively) and I am a little curious if any of you are that way, or how many would do what I do.
To sum up, some items on which to comment:
I cast the object first without asking about the cast. I use ReferenceEquals, not `=='. I return false inline with the if-statement; I don't use else.
When I say things like `I don't use else,' I don't mean all the time, but I don't use it if I don't need it. Does anyone know if this affects effeciency in any way? I suppose I'm too lazy to check out the disassembly (because it's always SOO confusing  ).
I look forward to hearing back from you, my esteemed colleagues.
In Christ,
Aaron Laws
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Aaron,
I teach C# at a local JC, and one thing I always stress is readability. White space and well defined blocks of
code are good because it allows your mind to process each item individually line by line, whereas this
Insets insets = obj as Insets;
if (ReferenceEquals(insets, null)) return false;
return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
forces me to stop and pick apart these lines to digest all that is happening.
I find this to me much clearer
if (obj is Insets)
{
Insets insets = obj as Insets;
return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
}
return false;
Also, one other thing we teach is having only one return in a method. It prevents "spaghetti code" where you
have to really hunt to see where the method is actually ending. So condider this:
bool bReturn = false;
if (obj is Insets)
{
Insets insets = obj as Insets;
bReturn = ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
}
return bReturn;
So now if I wanted to put more code in the method that I know will always run, all I have to do is find
the return & put the code above it.
Just my humble opinion.
Everything makes sense in someone's mind
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Kevin Marois wrote: Also, one other thing we teach is having only one return in a method
IMO, this makes the code hard to read. Multiple return is the preferred approach. Martin Fowler has a topic on this in his Refactoring book. I don't have it right now to quote.
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N a v a n e e t h wrote: Martin Fowler
But is he the only one who says that? I prefer to make my own decisions rather than follow the word of one author.
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I've not read enough books (or this one by Fowler) to know if other people say it, but I would personally prefer to use multiple return points. The reality is that in some cases, such as when you have cleanup code that must run and a try-finally isn't appropriate, you may need to have only one return point. Other than that, there is little to no mental benefit to doing it either way. When I read this,
bool bReturn;
if (condition)
{
bReturn = true;
}
else
{
if (other condition)
{
bReturn = false;
}
else
{
bReturn = true;
}
}
return bReturn;
I still have to trace through the same amount of code to know what the function will return each case, whether I use single or multiple returns. Allowing multiple returns makes it obvious when some condition will stop execution of the method immediately. If I must have a single return, these conditions end up causing if-else statements that I have to trace to the end of the method before realizing that, "Hey, this condition stops the method." This will also usually end up leading to deeper nesting, which is more difficult to read.
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Yes, that example may well be a good place for multiple returns, but it may also simply be a bad piece of code too.
My concern about having multiple returns is that it's too close to:
// do stuff
if ( exp ) goto end ;
// more stuff
end:
return whatever ;
In my opinion, multiple-return should be as uncommon as goto (that goes for continue and break (in loops*) as well).
Multiple-return, continue, break, and goto are the right tool for some jobs, but they shouldn't be the developer's first choice.
* Break and goto are required in switch statements  .
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Hi,
IMO readability is very important; it helps in getting correct code that is easily maintained.
Code generated and performance tend to be equal or better when you improve readability.
LimitedAtonement wrote: Insets insets = obj as Insets;
if (ReferenceEquals(insets, null)) return false;
return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
I seldom use "is", often "as", hardly ever ReferenceEquals, hence:
Insets insets=obj as Insets;
return insets!=null && insets.top==top && insets.left=left && insets.bottom==bottom && insets.right==right;
LimitedAtonement wrote: foreach (Point a in _gr_pts)
{
if (prev == Point.Empty || prev == a)
{
prev = a;
continue;
}
g.DrawArc(_ap_pen, prev, a);
prev = a;
}
isn't that just:
foreach (Point a in _gr_pts) {
if (prev!=Point.Empty && prev!=a) g.DrawArc(_ap_pen, prev, a);
prev=a;
}
You may have noted:
- I skip most irrelevant spaces
- I use "East Coast brackets", i.e. they open without a new line
- I use parentheses even when not needed to make sure about operator precedence but only if you could be mistaken.
- I don't use negative if conditions, unless there is no else, or the negative block is much much shorter than
the positive block (as in if (!OK) {throw} else {lots of code})
Luc Pattyn
I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages
Local announcement (Antwerp region): Lange Wapper? Neen!
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East Coast Brackets, I like the term. I usually just call it Java-style but yours is more fun.
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I never associated my bracket placement with Java, and I remember having had similar east/west discussions when being an active Java developer. I checked a few Java books and found both styles in use.
I've got the East Coast name long time ago, can't remember where from; and Google seems to have forgotten all about it too. But I continue to use and apply it.
Luc Pattyn
I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages
Local announcement (Antwerp region): Lange Wapper? Neen!
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They're why I left Boston for California. 
(Not really.)
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LimitedAtonement wrote: I use ReferenceEquals, not `=='
You don't get any advantage of doing this. Objects are by default compared by reference. Your first sharpified code looks good. IMO, readability of code is subjective. I'd write something like
Insets insets = obj as Insets;
return insets == null ? false : ((top == insets.top) && (left == insets.left)
&& (bottom == insets.bottom) && (right == insets.right));
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No need for the trinary operator. Otherwise, 5.
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I too thought the same after posting. Probably more cleaner approach would be
Insets insets = obj as Insets;
if(insets == null)
return false;
return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
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The only use I've found for ReferenceEquals is null checking in classes that overload operators == and !=.
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Dave,
But why would a class overload the == operator and not handle null itself? Do you see this often? I also thought this, but reconsidered recently. The reason I was using ReferenceEquals is because I don't want to have to check to see if it has an overload, then check to see if it returns properly with null.
In Christ,
Aaron Laws
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I meant within the class itself. Consider this int wrapper class (I've just written it out quickly so is very rough!) and compare the two different == operator overloads...
public class MyIntWrapperClass : IEquatable<MyIntWrapperClass>
{
private int _Value;
public MyIntWrapperClass(int value)
{
_Value = value;
}
public static bool operator ==(MyIntWrapperClass a, MyIntWrapperClass b)
{
bool result = false;
if (!ReferenceEquals(a, null))
{
if (!ReferenceEquals(b, null))
result = a._Value == b._Value;
else
result = false;
}
else
result = ReferenceEquals(b, null);
return result;
}
public static bool operator !=(MyIntWrapperClass a, MyIntWrapperClass b)
{
return !(a == b);
}
public int Value
{
get { return _Value; }
}
public override bool Equals(object obj)
{
return Equals(obj as MyIntWrapperClass);
}
public bool Equals(MyIntWrapperClass other)
{
return this == other;
}
public override int GetHashCode()
{
return _Value; ;
}
public override string ToString()
{
return _Value.ToString();
}
}
modified on Wednesday, October 7, 2009 5:24 PM
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LimitedAtonement wrote: I do this kind of thing ALL the time
So your job is to edit and refactor code?
From a performance and readability perspective I saw nothing wrong with the first snippet, except the casting the object twice (once for the is comparison and once for the as). If you had been working for me I'd question why you were wasting time like this.
All of the coding standards I have used call for curly braces with control statements and one statement per line. It is not only more readable but helps when debugging to see what statement is being executed.
Not checking an object after doing a cast, or as in this case, is just plain stupid.
only two letters away from being an asset
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Don't hold back. Tell him what your really think.
Everything makes sense in someone's mind
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