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Abstract class and inheritance is all about building a hierarchy (or family) of classes while Interface is to enforce a contract.
Consider this hierarchy of classes. You can create FlyingVehicle as an abstract class.
Vehicle --> FlyingVehicle --> Helicopter
Consider another hierarchy of classes. You can create Bird as an abstract class.
Animal --> Bird --> Eagle
While the two families of classes are distinct, both the the FlyingVehicle and the Bird classes can implement an Interface called IFlyable.
interface IFlyable {
void Fly();
void Land();
}
As you can see in this example, you created two distinct families of classes using Abstract classes and enforced the ability to fly using an interface.
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Mr.Shameel,
Can you please make those example's little clear, mean to say.. describing interface & abstract class with the same example by inheriting.
krishna
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That's the point here, abstract classes and interfaces are not meant to be used interchangeably (although most programming languages allow you to do that). Classes are to build family and interfaces are to enforce contracts, nothing more, nothing less.
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krishnavaradharajan wrote: I know the functionality of Abstract Class & Interface.
Normally the "functionality" has nothing to do with the decision.
You use them because they meet the design needs.
krishnavaradharajan wrote: How to find out which is suitable for particular situation.
1. Collect some requirements.
2. Create a design.
3. Use the design to implement code.
Step 3 is where you decide which one to use based on the objects of the design.
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Hi,
I know the functionality of sqlcommandBuilder.
But when to use sqlcommandbuilder instant of sql query.
If sqlcommandBuilder does everything( insert/update/delete ), than why I required sql query's. I can do everything through sqlcommandBuilder rite.
Is there any particular sinario that i can use sqlcommandBuilder or I cant use sqlcommandBuilder ?
krishna
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krishnavaradharajan wrote: If sqlcommandBuilder does everything( insert/update/delete ), than why I required sql query's.
It doesn't do "everything", just the crud-operations. It's not used when creating a table using a query, or when things get complex. As the documentation states, it only generates a single-table update.
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
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Hi Mr.Eddy,
So you mean to say that, commanbuilder can be used only for simple and single query operation.
Another thing is, consider I have a dataset(ds) of 1000 records, and how do I edit dataset, means how to update without using commanbuilder and fetch only updated rows from ds.
krishna
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krishnavaradharajan wrote: So you mean to say that, commanbuilder can be used only for simple and single query operation.
Yup. It's a shortcut, an easy way to generate a simple query.
krishnavaradharajan wrote: Another thing is, consider I have a dataset(ds) of 1000 records, and how do I edit dataset, means how to update without using commanbuilder and fetch only updated rows from ds.
The GetChanges method will give you everything that changed in the dataset.
Bastard Programmer from Hell
If you can't read my code, try converting it here[^]
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You're welcome 
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krishnavaradharajan wrote: when to use sqlcommandbuilder
Never.
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Do you have any particular reason to say never..
krishna
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Experience.
It has always bitten me with its limitations. Plus it's closely associated with DataAdapter which is even worse.
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Thank you..
krishna
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I am trying to develop a very simple wireless sensor node simulator using C#. I have figured out how to "divide" the simulation time into different "states" of the sensor node but I am currently having some problems on how to properly implement a global simulation time for all the sensor nodes.
Here's what I did so far but I am sure there is a much better way to do this.
I made a NODE class which contains a Run() method that has a for loop executed to simulate time. But the obvious problem is, if I duplicate this NODE class to make other nodes (5-10 other nodes), there's a tendency that they will not be synchronized (especially when they communicate with each other).
public void Run()
{
for (int i = 0; i < 1000; i++ )
{
if (sleep)
{
if (csleep < timeToSleep)
{
Sleep(i);
csleep++;
}
else
{
sleep = false;
csleep = 0;
wakeup = true;
}
}
if (wakeup)
{
if (cwakeup < timeToWakeUp)
{
WakeUp(i);
cwakeup++;
}
else
{
wakeup = false;
cwakeup = 0;
listen = true;
}
}
if (listen)
{
...same as above code...
}
if (send)
{
...same as above code...
}
if (receive)
{
...same as above code...
}
}
Console.WriteLine("END SIMULATION");
}
So, when I execute the nodes in the main simulation class, it looks like this:
class Program
{
static void Main(string[] args)
{
Node node1 = new Node();
Node node2 = new Node();
node1.Run();
node2.Run();
}
}
The above codes are obviously incorrect since the simulation time is placed inside each node object. What I am trying to do is this:
I want to treat all nodes as if they are threads communicating with each other or could sometimes just independently "exist" in the simulation. But how do I make it that all of these nodes could have one single basis for the simulation time?
Simulation loop
{
Node 1 executed;
Node 2 executed;
}
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Unless NODE has some sort of interrupt mechanism (Sleep; I/O; etc.), once one is “Run”, it will hog the (one) thread indefinitely.
I would suggest putting the “timing” code in a separate class (or in static methods of the NODE base class), and use a “Timer” instead of a “for” loop for invoking “sleep”, “awake”, etc. states.
Prior to creating and “running” a NODE, start the “timing” object / static methods.
As a NODE is created, it should subscribe to (state-change) events in the timing object that call the “Sleep”, “Awake”, etc. event handlers in a subscribing NODE.
In this way, the timing object will call the “Sleep”, “Awake”, etc. methods in each (subscribing) NODE with each “state” change (i.e. x number of ticks of the Timer).
This of course assumes you want all NODEs to be “asleep” or “awake”, etc. at the same time.
You will need some sort of (message) queuing mechanism to actually “communicate” between these NODEs; since if they are all “sending” at the same time (state-wise), they can also not be “receiving” at the same time.
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Thanks Gerry! I will try your suggestions
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You're welcome. Glad I could help.
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Hello experts,
I'm quite new to dotnet programming and so on, so perhaps my question is very easy to answer.
I'm sending data from a µC to PC over USB. This is byte wise and when I want so send a float, I did it like in this C++ test code and it worked:
int _tmain(int argc, _TCHAR* argv[])
{
char test[4] = {25,4,158,63};
float *blubb = (float*)&test[0];
printf("%f",*blubb);
return 0;
}
Now I want to do the same in C# and it doesn't work. Here is my attempt:
namespace csharpfloattest
{
class Program
{
unsafe static void Main(string[] args)
{
byte[] test = { 25, 4, 158, 63 };
fixed (float* p = (float*)test)
{
Console.WriteLine(*p);
}
}
}
}
Compiler gives out this error:
Cannot convert type 'byte[]' to 'float*'
Perhaps someone can give me an advice?
Thanks for your help!!
Florian
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I would suggest using BitConverter.ToSingle to convert bytes to a float, and BitConverter.GetBytes to convert a float to bytes.
Depending on the architecture of the sender and receiver (little versus big Endian), you may have to consider byte ordering.
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Thanks a lot! Didn't know this method...
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In general, c# (or any managed .NET language) does not have pointers.
(Yes, there's unsafe and IntPtr but that is not necessary to accomplish what you've described.)
The way to do this kind of thing in c# is to use the class System.BitConverter.
So to convert a byte[] into a float is:
class Program
{
static void Main(string[] args)
{
byte[] test = { 25, 4, 158, 63 };
float p = BitConverter.ToSingle(test, 0);
Console.WriteLine(p);
}
}
Going the other way, from float to byte[], you would use BitConverter.GetBytes(value);
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You can't cast an array to a pointer (not even a fixed-size array). But you can take the address of the 0th item of the array, and then attempt to cast that:
fixed (float* p = (float*)&test[0])
{
}
But that turns out to be explicitly forbidden: "The right hand side of a fixed statement assignment may not be a cast expression".
So there's not much choice, you'd have to do something like this:
fixed (byte* temp = data)
{
float* p = (float*)temp;
}
There was the alternative of not using unsafe code (not directly anyway, BitConverter.ToSingle is implemented using unsafe code itself) in this case, so this is just for completeness really.
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i got a routine which said that it will highlight word in word document but it is giving error "Bad variable type. (Exception from HRESULT: 0x80020008 (DISP_E_BADVARTYPE))"
when this below line execute then exception occur and error as above occur.
range.find.highlight()
here is my full code
private static void HighlightText()
{
object fileName = "D:\\CVArchievePath\\C0000000001.doc";
object textToFind = "test1";
object readOnly = true;
Word.Application word = new Word.Application();
Word.Document doc = new Word.Document();
object missing = Type.Missing;
try
{
doc = word.Documents.Open(ref fileName, ref missing, ref readOnly,
ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing,
ref missing);
doc.Activate();
object matchPhrase = false;
object matchCase = false;
object matchPrefix = false;
object matchSuffix = false;
object matchWholeWord = false;
object matchWildcards = false;
object matchSoundsLike = false;
object matchAllWordForms = false;
object matchByte = false;
object ignoreSpace = false;
object ignorePunct = false;
object highlightedColor = Word.WdColor.wdColorGreen;
object textColor = Word.WdColor.wdColorLightOrange;
object missingp = false;
Word.Range range = doc.Range();
bool highlighted = range.Find.HitHighlight(ref textToFind,
ref highlightedColor,
ref textColor,
ref matchCase,
ref matchWholeWord,
ref matchPrefix,
ref matchSuffix,
ref matchPhrase,
ref matchWildcards,
ref matchSoundsLike,
ref matchAllWordForms,
ref matchByte,
ref missingp,
ref missingp,
ref missingp,
ref missingp,
ref missingp,
ref ignoreSpace,
ref ignorePunct,
ref missingp);
System.Diagnostics.Process.Start(fileName.ToString());
}
catch (Exception ex)
{
Console.WriteLine("Error : " + ex.Message);
}
}
tbhattacharjee
modified 8-Mar-13 7:45am.
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