Re: How to control the controls of another form from current form - C# Discussion Boards

Re: How to avoid from copy of windows in Visualg .Net C#

9-Dec-06 4:26

Hi,

just use the search[^] function.

Robert

mav.northwind9-Dec-06 4:28

mav.northwind

9-Dec-06 4:28

Search the forums and articles for "single instance", these are the right keywords you are looking for.

Regards,
mav

--
Black holes are the places where God divided by 0...

Re: How to avoid from copy of windows in Visualg .Net C#

karam chandrabose9-Dec-06 9:08

karam chandrabose

9-Dec-06 9:08

u would have to use MUTEX variable to maintainn single instance

Re: System.Security.Cryptography.RSAParameters

edchan9-Dec-06 3:49

edchan

9-Dec-06 3:49

Hi,
I want to know how to create my own public & private key pairs, is it correct to use the following codes? And what are valid parameters P, Q, Modulus, any sample codes?

----------------------------------------------------------------------
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(1024);
System.Security.Cryptography.RSAParameters parameters = new System.Security.Cryptography.RSAParameters();
parameters.P=???;
parameters.Modulus=???;
.............
...............
rsa.ImportParameters(parameters)

----------------------------------------------------------------------

Thanks & best regards,
Ed.

Add Cotrol Problem

MHASSANF9-Dec-06 3:21

MHASSANF

9-Dec-06 3:21

I have a Problem To add dynamic control to the Form

i save the controls in array list but when i add the control to Form The added ( the count property of this.Controls updated) But they areen' add to Form ( can't see any thing)
my code is :

int count = 1;
foreach (MyControl _control in ArrayList)
{

this.Controls.Add(_control);
_control.Location = new Point(count * 20, count *20);
count++;

}
What's The Problem

?
With Thanks

MHF

Re: Add Cotrol Problem

Robert Rohde9-Dec-06 4:24

Doubt on C# virtual functions

9-Dec-06 4:24

Hi,

I would first check if the Size and Visible properties of the added controls are correct. Other than that the code principally looks fine.

Robert

Re: Add Cotrol Problem

MHASSANF10-Dec-06 2:55

MHASSANF

10-Dec-06 2:55

I think Problem is that i read the control's data from ArrayList
because when i use the 'new' keyword that's work

if is it true ?

With Thanks

MHF

jithus9-Dec-06 2:30

9-Dec-06 2:30

The following is a question i faced in an interview...They asked me the ouput of the following code snippet

using System;<br />
<br />
namespace CsharpTestQ<br />
{<br />
	public class ClassA<br />
	{<br />
		public virtual void printStr()<br />
		{<br />
			Console.Write("A");<br />
		}<br />
	}<br />
<br />
	public class ClassB:ClassA<br />
	{<br />
		public override void printStr()<br />
		{<br />
			Console.Write("B");<br />
		}<br />
	}<br />
<br />
	public class ClassC:ClassB<br />
	{<br />
		public virtual void printStr()<br />
		{<br />
			Console.Write("C");<br />
		}<br />
	}<br />
<br />
	public class ClassD:ClassC<br />
	{<br />
		public override void printStr()<br />
		{<br />
			Console.Write("D");<br />
		}<br />
	}<br />
<br />
	class Class1<br />
	{<br />
		<br />
		[STAThread]<br />
		static void Main(string[] args)<br />
		{<br />
<br />
			ClassD d=new ClassD();<br />
			ClassA a=d;<br />
			ClassB b=d;<br />
			ClassC c=d;<br />
<br />
			a.printStr();<br />
			b.printStr();<br />
			c.printStr();<br />
			d.printStr();<br />
<br />
			Console.ReadLine();<br />
			<br />
		}<br />
	}<br />
}

I thought it would be "DDDD" since the object is the same (d) and the vtable in "d" points to the function printStr in ClassD. But when i tried it, the output is "BBDD". Can any one explain what is happening here?

Robert Rohde9-Dec-06 2:48

9-Dec-06 2:48

Hi,

class C shadows the printStr function and thus every call on C or D will call the new function. When compiling this I would think the C# compiler should give out a warning, because normally a explicit new should be put onto the shadowing method declaration.

Robert

jithus9-Dec-06 3:35

9-Dec-06 3:35

Hi,

Thanks for the reply.

Does this mean that when an object of ClassD is created there's actually two implementation of "printStr" (old and new)within the object? how does the runtime determine which function to call?

Jithu

Robert Rohde9-Dec-06 4:22

9-Dec-06 4:22

Hi,

the implementation of the function is not hold within the object, but yes the class has two different implementations. Which one is called is already determined at compile time. There is another fancy behavior like this when working with explicit interface implementations:

public interface ITest {
   public string GetString();
}

public class TestClass : ITest {
   public string GetString() {
      return "A";
   }

   string ITest.GetString() {
      return "B";
   }
}

Now guess what the output of the following code is...

TestClass testClass = new TestClass();
ITest testInterface = testClass;
Console.Write(testClass.GetString());
Console.Write(testInterface .GetString());

The output is AB. Smile | :)

Robert

jithus9-Dec-06 6:08

9-Dec-06 6:08

Hi,

Thanks!!!

Basic Inheritance in itself is difficult...and these fancy feautures aren't making things easier... Frown | :(

When do we apply these concepts of Shadowing and explicit interface in our code?

Jithu

Robert Rohde9-Dec-06 9:16

9-Dec-06 9:16

Hi,

explicit interface implementations are nice for interfaces like IClonable. The Clone method of IClonable always returns an object (I know there is also a generic version but thats another story). But in most case you also want a typesafe version. With explicit interface implementation you can implement ICloneable while still supplying a typesafe Clone method:

public class Test : IClonable {
   public Test Clone() {
      //Clone the object
   }

   IClonable.Clone() {
      return this.Clone();
   }
}

So if you call clone on a variable typed to Test you will also get a Test instance while you'll get an object when working on the interface.

Shadowing can also be useful. Lets assume you have an interface which has a Name property. Lets also assume you have some user control which should implement this interface. Now you have the problem that the Name property from the user control (inherited from Control) does have a complete different meaning than the Name property of your interface. You could even break the designer when changing the normal Name property. Thus you could either use explicit interface implementation (see above) or use shadowing. When using the new keyword on your Name property it will look like a normal property and can be used as an implicit interface implementation. But everyone using the Name property from a Control typed variable (like the designer does) still gets the same behaviour as before.

Robert

jithus10-Dec-06 3:22

10-Dec-06 3:22

Thanks...The examples were gr8...Now i have got some idea where to apply the concepts...