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georgemathew2@hotmail.com wrote: what is the difference b/w abstract method and interfaces
I think you mean an abstract class and interface.
An abstract class is a class that cannot be instantiated. However, it can contain members (fields, properties, methods, etc.). Some members can be declared as abstract which means that they do not provide any functionality and any derived class is required to implement the behaviour.
An interface does not contain any functionality or data. Some descibe it as providing a contract. If you implement the interface then you are contractually obliged to implement the members it specifies.
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Nothing, but then you asked the wrong question
You should have asked "What is the difference between an abstract class and an interfaces?"
In which case the answer would have been that an abstract class can contain some implementation detail whereas an interface just defines a contract that an implementing class must conform to.
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Hi
I guess you mean between an abstract class and an interface.
An Interface is basically an abstract class.
with an abstract class you define a class that can not be instanced with new
the abstract class example of this interface:
public interface MyInterface
{
void Foo(int Param);
}
would be:
public abstract class MyAbstractClass
{
public abstract void Foo(int Param);
}
so you see 2 important differences:
1) in an interface you don't need a modifyer as public/private/internal on the members. they all have the same visibility as the interface (int this case public)
2) in an interface every member is implicit abstract.
but still there's a difference between an interface and a class.
in an abstract class you can do this:
public abstract class MyAbstractClass
{
protected int myProtectedMember;
public abstract void Foo(int Param);
Public MyAbstractClass()
{
myProtectedMember = 100;
}
protected virtual void Inc(ref int Value)
{
Value++;
}
}
--> you can implement functions that are accessible by a derived class only. a protected member is a private member that is visible for derived classes as well.
--> the interface won't let you implement fuctions directly on it.
--> an interface can not have a constructor
and one more important difference between an abstract class and an interface:
you can derive a class from exactly one other class, but from as many interfaces you want.
there are some more differences (like implementation of classes that inherit a class/interface) but you'll see if you try
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In my experience "b/w" means "backed with" so I have no idea what your question means.
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Hi
I was wondering one thing about threads. Lets assume I have only a console application with a main thread running. Then lets assume I spawn multiple threads working with some intensive operations for a few minutes. Now, In the main thread I want some way of knowing the exact moment each of the new threads are done executing, in addition to providing feedback during the entire progress. The idea was that the threads would execute a method in the main thread the moment they are done executing.
How I see it this can only be done by adding some sort of "main loop" in the main thread which looks at an event queue and run these events. The other threads must then push a new event on the thread queue (and make sure this queue is thread safe I assume) before they die.
So here is the question: How I solve this problem using nothing more than the standard libraries? Is there any way I can block the main thread until it receives a signal from another thread (kinda like pthreads library for C)?
I assume someone will suggest BackgroundWorker, but I have tried this and the part with giving progress (not as a % number, but as executing methods on the main thread whenever an update is due) seemed hard. I have also looked into the beginInvoke/endInvoke asynchronous execution, but also here the interactive feedback seems to be an issue.
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Notification events are always nice.
Need a C# Consultant? I'm available.
Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway
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Hi,
I have millions of 3D line segments. Each segment is denoted by a point at a each end. One line segment would be v1, v4 (where v1 and v4 are x,y,z). If multiple lines radiate out from one point there will be multiple lines for that point (theoretical v1 could have an infinite number of lines radiating out). There is no ordering in the assignment of x,y,z to points or in the number of points- both are random. There may be 2 or more line segments which form a continuous straight line (v1, v4, v17, vn). I want to find those longer lines and have a single segment replace the multiple segments (v1, v4, v17, vn results in v1, vn). I have been experimenting with the dot product (a result of 1 or -1 is a straight line) and it works. I also have processor and memory issues (neither unlimited) and a time constraint. My question, is there a more efficient way to search for the line segments which form a straight lines (lose the square root) and is there a way to search for line segments radiating from a point (currently I have O^2, unacceptable). Thanks in advance for any help.
-- modified at 12:29 Monday 26th November, 2007
I have developed an efficient routine for finding if line segments are straight continuations of previous lines. Wondering if anyone knows of a search which can be done in a reasonable time frame?
this thing looks like it was written by an epileptic ferret
Dave Kreskowiak
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If there is a bound on the x, y, and z coordinates, then you could do an O(n) sort on all the endpoints. Otherwise, just use a sortedDictionary structure to keep the hash of the endpoints (combine the values of x, y, and z to produce h such that x, y, and z can be retrieved by only knowing h) and a list of indices where that endpoint is contained. Then searching for all line segments "radiating" from the endpoint is easy. This will NOT work, however, for lines that contain other lines but have different endpoints. For example, I think your goal is to combine the lines <0,0,0> to <2,2,2> with <1,1,1> to <3,3,3> to form the line <0,0,0> to <3,3,3>. This is a non-trivial computation, and you will have to solve a system of equations to find out if these two lines can be combined.
Jeff
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I did give a hash some thought, was worried about the size. I have not looked at sortedDictionary, will do so thanks.
I am leaning towards an endpoint ordering. Concern with that approach is the time to form the line. Aren't modern machines supposed to remove this time/memory problem with lots of each.
The original data contains no 'lines with in lines' each segment is unique. Using your example the lines would be <0,0,0> to <1,1,1> and <1,1,1> to <2,2,2> and <2,2,2> to <3,3,3> resulting in a line of <0,0,0> to <3,3,3>. The overlap from your example is not possible in the data set I am working with, if it does occur there was an error beyond my control.
this thing looks like it was written by an epileptic ferret
Dave Kreskowiak
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Then just do what I suggested before, and use sorted dictionary to automatically sort the endpoints for you. You don't even have to use a hash if the class "Point3D" implements IComparable and IEquatable (you can just use the point directly as the key). It would be something like this...
public class Point3D : IComparable<Point3D>, IEquatable<Point3D> {
// this class must implement VALUE comparison (NOT REFERENCE!)
}
public class LineSegment {
public Point3D EndPoint1 { get; }
public Point3D EndPoint2 { get; }
public Vector Slope { get; }
}
public class SomeOther {
List<LineSegment> m_LineSegments = ...; // populate field
SortedDictionary<Point3D, IList<int>> m_EndPoints;
public void AddEndpoint(Point3D pt, int i) {
if (!m_EndPoints.ContainsKey(pt))
m_EndPoints.Add(pt, new List<int>());
m_EndPoints[pt].Add(i);
}
public void CombineLineSegments() {
m_EndPoints = new SortedDictionary<Point3D, IList<int>>(m_LineSegments.Count);
Point3D pt;
for (int i = m_LineSegments.Count - 1; i >= 0; --i) {
AddEndpoint(m_LineSegments[i].EndPoint1, i);
AddEndpoint(m_LineSegments[i].EndPoint2, i);
}
List<int[]> segsToCombine = new List<int[]>();
// Now iterate through the list of endpoints, checking each segment
// for direction coming out of that point. If direction matches, add
// the indices for those vectors to the segsToCombine list
// Finally, combine the segments found to be combinable.
}
}
Jeff
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Thanks for the help. Sorry for the late reply, I have been out of the office for a couple of days.
Jim
this thing looks like it was written by an epileptic ferret
Dave Kreskowiak
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jimwawar wrote: lose the square root
where is the sqrt coming from?
Luc Pattyn [Forum Guidelines] [My Articles]
this months tips:
- before you ask a question here, search CodeProject, then Google
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get
- use PRE tags to preserve formatting when showing multi-line code snippets
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sqrt was coming in the dot product calculation. The vector was being calculated from the two end points.
The length of the line segment needs to be brought to unit length before the dot product will result in the angle between the two lines. So to bring vector <a,b,c> to unit form length = sqrt(a*a + b*b + c*c) unit form is .
this thing looks like it was written by an epileptic ferret
Dave Kreskowiak
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Can't you live with just the square of length, skipping the sqrt all together?
Furthermore, you're looking for a zero angle, that should be inexpensive.
In two dimensions, I don't think I need any length:
the line defined by points (x1,y1) and (x2,y2)
may connect to the line defined by points (x3,y3) and (x4,y4) if:
- the two lines have the same orientation and origin
- the end points of the line segments are such that they touch or overlap
orientation and origin can easily be tested based on the line's equation:
(y - y1) * (x2 - x1) = (x - x1) * (y2 - y1)
so this equation must hold for x=x3,y=y3 as well as for x=x4,y=y4
Adding a third dimension adds one more equation (say with z and x)
Hope this helps.
Luc Pattyn [Forum Guidelines] [My Articles]
this months tips:
- before you ask a question here, search CodeProject, then Google
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get
- use PRE tags to preserve formatting when showing multi-line code snippets
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Luc Pattyn wrote: Hope this helps.
It does, thanks
this thing looks like it was written by an epileptic ferret
Dave Kreskowiak
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I have a master page and there is a tree view control there and this is one of the treenodes.
TreeNode _Del = new TreeNode();
_Del.Text = "Administrator";
_Del.NavigateUrl = "~\\Form1.aspx";
TreeNode _Del1 = new TreeNode();
_Del1.Text = "Manager";
_Del1.NavigateUrl = "~\\Form1.aspx";
There is a Form1 and the form1 has two panels. If treenode corresponding to _Del is clicked, panel1.visible=true, panel2.visible=false
and if _Del1 is clicked, panel1.visible=false, panel2.visible=true
Question: How do I get which treenode am clicking in the Form1?
Is response.redirect querystring the only option?
Please help and if the post is not clear, please mention. I can more clearly tell you.
Thanks
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ss.mmm wrote: TreeNode _Del = new TreeNode();
_Del.Text = "Administrator";
_Del.NavigateUrl = "~\\Form1.aspx";
as you are navigating to the same URL, so quick fix is to add a parameter in the URL like:
<br />
_Del.NavigateUrl = "~\\Form1.aspx?node=1";<br />
<br />
and <br />
<br />
_Del1.NavigateUrl = "~\\Form1.aspx?node=2";
and in the code you can show and hide the panels based on node.
-----
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Bad news I know. Does this extend to altering the Tag property on a control too though? I'm stuck in a .NET 1.1 environment (God, give me strength....) so I don't get any helpful exceptions showing me the way.
Regards,
Rob Philpott.
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Hi
As far as i know the cross thread exceptions came up with .net 2.0 so theory says you should be able to change a property of a control from a non-gui thread in 1.x.
but.
as in .net 2.0, 1.1 has the property invokeRequired too. so you can do the same as in 2.0 with Control.Invoke(....)
greets
m@u
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Hey, thanks for the reply.
I know the exceptions were introduced in 2.0, but the rule certainly appied before that. The problem is most the time you'd get away with it, but on occasion it would go wrong so they decided to enforce it in version 2.
Regards,
Rob Philpott.
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Ok then i'm lucky i think i still have some (very..) old code that does that ugly cross-thread thing without invoke..
anyway.. you said you don't get a meaningful exception. do you get an exception at all or does the app just hang?
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Hi,
a thread that did not create a Control, should not access that Control, except for the
very few members explicitly allowed, including InvokeRequired and Invoke (but not Tag).
Before .NET 2.0 the app may behave badly, the GUI may freeze, anything can go wrong if
you violate the rule.
Since 2.0 you get an InvalidOperationException by default; you can disable that by setting
Control.CheckForIllegalCrossThreadCalls false, but that is a very bad idea, and it brings
you back in the previous situation.
Since most if not all Controls are somehow related (they are on a Form, one Form owns
another Form, etc), the natural consequence is all Controls get created and accessed
exclusively by a single thread, typically your initial or main thread, often also called
the "GUI thread".
There are lots of examples on InvokeRequired/Invoke available everywhere;
a rather advanced article on the subject is here[^].
Luc Pattyn [Forum Guidelines] [My Articles]
this months tips:
- before you ask a question here, search CodeProject, then Google
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get
- use PRE tags to preserve formatting when showing multi-line code snippets
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I am trying to insert data into excel, i usually have no problems, i only have one specific problem:
If the Column Header is named "Job#" the Insert satement fails because it says it can't find column Job#. i have tried everything i can think of to get the # escaped so it doesn't think its a special character. I am using the OLEDB provider to insert with the excel Jet object. Anyone have any advice?????
Thanls
Marios
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Try using (char)35 - I have sometimes found this can work in the sort of situation you are describing.
Regards
Guy
You always pass failure on the way to success.
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