Garbage Collection - Question - C# Discussion Boards

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Re: win form

Polis Pilavas24-Apr-05 3:14

Polis Pilavas

24-Apr-05 3:14

vuthaianh wrote:
Could i reference to a windows form from another

Ofourse you can. A form is a class like everything else. If you have assigned public variables or methods in the class you want to access then you can access them from any other class in your solution.

E.g. you have 2 classes, Form1 and Form2 and you want to access Form2 from Form1.
(1) First of all you create one instance of each class:

Form1 <code>myFirstForm </code>= new Form1();
Form2 <code>mySecondForm </code>= new Form2();

(2) Assuming that you have publicly available fields or methods in Form2 then you can access them from any class, including Form1. So if you wanted to call a method located inside Form2 from somewhere within Form1 you could say:

int <code>myRate </code>= mySecondForm.CalculateRate();

Hope this helps

Regards,
Polis

Can you practice what you teach?

Re: win form

Nick Parker24-Apr-05 4:35

Nick Parker

24-Apr-05 4:35

One thing that Polis didn't mention was the use of events and delegates. You can hook into events that another form (i.e., FormB) exposes to notify your main form (i.e., FormA). This will allow you to maintain private methods across both forms and still transfer data.

- Nick Parker
Microsoft MVP - Visual C#
My Blog | My Articles

Re: win form

Polis Pilavas24-Apr-05 6:52

Polis Pilavas

24-Apr-05 6:52

Yes, Nick makes a good point there with events and delegates. I guess the rest is up to you

Regards,
Polis

Can you practice what you teach?

Execute Stored Procedure...

Illegal Operation24-Apr-05 2:53

Illegal Operation

24-Apr-05 2:53

How do I execute a stored procedure in the Page_Load function of C#?

Thanks!

Illegal Operation

WannaBe and GonnaBe Systems Developer

Re: Execute Stored Procedure...

Colin Angus Mackay24-Apr-05 3:42

Colin Angus Mackay

24-Apr-05 3:42

The same way you would execute a stored procedure anywhere else.

I'll assume you are using SQL Server 2000

SqlConnection conn = new SqlConnection(myConnectionString);
SqlCommand cmd = new SqlCommand(storedProcName, conn);
// Add any parameters to the command here
conn.Open();
// Run only one of the following lines depending on what you are expecting.
cmd.ExecuteNonQuery(); // Sproc returns no data 
myValue = cmd.ExecuteScalar(); // Sproc returns a single value 1st col 1st row
myReader = cmd.ExecuteReader(); // Sproc returns many rows

// Everything done. close the connection.
conn.Close();

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Re: Execute Stored Procedure...

Illegal Operation24-Apr-05 4:05

Illegal Operation

24-Apr-05 4:05

thanks for the help.

Just one more question?

Where does the "myReader" fit into the picture? I have inserted the line:

myReader = MyProc.executeReader();

Thanks!

Illegal Operation

WannaBe and GonnaBe Systems Developer

Re: Execute Stored Procedure...

Colin Angus Mackay24-Apr-05 4:11

Colin Angus Mackay

24-Apr-05 4:11

Illegal Operation wrote:
Where does the "myReader" fit into the picture?

It is a SqlDataReader. e.g.

SqlDataReader myReader = myProc.ExecuteReader();

You will then need to set up a loop to iterate through all the rows. e.g.

while(myReader.Read())
{
    // use the SqlDataReader's Get... methods to extract the data.
}

You can find out more about Execute reader from the MSDN Documentation[^]

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Garbage Collection - Question

Tristan Rhodes24-Apr-05 0:33

Tristan Rhodes

24-Apr-05 0:33

I have an item that is a tag value to a list view, and the list view item is also contained in the object. The relationship is two way.

My question is, if i remove these objects, will it persist in memory due to the fact that they refference each other?

From what i've read of the Garbage collector, it will perform a graph search for all objects reachable from root objects. So even if my two objects DO refference each other, they will be removed if they are unreachable from the root objects.

Is this right?

Cheers

Cata

Re: Garbage Collection - Question

WillemM24-Apr-05 2:20

WillemM

24-Apr-05 2:20

That's right. It will remove them.

WM.

What about weapons of mass-construction?

Including a manifest file within the exe file

Anonymous23-Apr-05 23:34

Anonymous

23-Apr-05 23:34

Hi, is it possible to include the myApp.exe.manifest file in the exe file so that I don't have to have two separate files, one exe and one manifest? If so, how should I do this? (Visual Studio .NET 2003, C#)

Re: Including a manifest file within the exe file

DavidNohejl24-Apr-05 2:06

DavidNohejl

24-Apr-05 2:06

http://www.codeproject.com/csharp/dotnetvisualstyles.asp[^]

Never forget: "Stay kul and happy" (I.A.)

David's thoughts / dnhsoftware.org / MyHTMLTidy

windows services

sianatia23-Apr-05 23:18

sianatia

23-Apr-05 23:18

hi,
i have made a service wich loads a another program ,my codes are correct but when i use these codes in my service,they dont work.
here is my codes:

<br />
System.IO.Directory.SetCurrentDirectory(myappPath);<br />
Process.Start("MyApplication" );<br />

i want to know why it happens?

Re: windows services

Claudio Grazioli24-Apr-05 6:14

Claudio Grazioli

24-Apr-05 6:14

What does not work?

Does the application not start? Have you checked with the TaskManager if it really does not start or is it started and you can't just see it?

Normally, a service application cannot interact with the desktop. Because of that, if you start an application from a service, the application will not be visible to the user.

To allow a service to interact with the desktop open the Service Control Manager. Select your service and open the properties.
- Select the "Log On" tab
- Select "Log on as: Local System account" and enter a valid account and password
- Check "Allow service to interact with desktop.

hth

Claudio
Claudio's Website
Hommingberger Gepardenforelle

List the files in another computer

Johny Ng23-Apr-05 18:58

Johny Ng

23-Apr-05 18:58

Hi folks,

I need to write a piece of code that will list all the files in a folder in another machine.
Could you guys give me a hint?

Thanks.

Re: List the files in another computer

lubos_h24-Apr-05 2:06

lubos_h

24-Apr-05 2:06

you can set up the sharing on the another computer and access the directory directly using System.IO.Directory or make some sort of simple service which will send the data on request via tcp/ip protocol.

Value Types Vs Reference Types

vchedalla23-Apr-05 18:57

vchedalla

23-Apr-05 18:57

1.Value types are allocated on stack and Reference types are allocated on heap,managed by garbage collector.
if reference type contains value type as a member,where does meomory allocated for value types?
eg: class employee
{
int i; //stack or heap? or some boxing?
}
2.Value types are initialized to zero or null. does reference type member variables are initialized to zero or null?

Thanks
Viny.

Re: Value Types Vs Reference Types

Colin Angus Mackay23-Apr-05 22:42

Colin Angus Mackay

23-Apr-05 22:42

vchedalla wrote:
if reference type contains value type as a member,where does meomory allocated for value types?

On the heap with the rest of the reference type.

The idea that value types are always created on the stack is not correct. If you have a method that creates a value type as part of its operation then it will be created on the stack, when the method ends it will be removed from the stack, along with everything else that was created on the stack during the method - and that includes any references to objects (NOTE: not the actual object - that will be done by the garbage collector if there are no other references to the object)

When a value type is a member variable of an object then it will be placed on the heap as it would not be logical to put it on the stack. A stack, as the name suggests, is built up as values are placed on it, and brought down as they are removed. You cannot remove a value from the middle of the stack.

vchedalla wrote:
Value types are initialized to zero or null. does reference type member variables are initialized to zero or null?

Value types cannot be initialised to null, but they can be initialised to some default value (like 0). Reference types are initialised to null.

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using the serial port

Mridang Agarwalla23-Apr-05 18:06

Mridang Agarwalla

23-Apr-05 18:06

i have a remote control, whose sensor is attached to the serial port. I would like to know how to use the serial port in .NET so i can create custom applications for the remote....

Re: using the serial port

Peter Ritchie24-Apr-05 8:21

Peter Ritchie

24-Apr-05 8:21

Check out http://msdn.microsoft.com/msdnmag/issues/02/10/netserialcomm/[^] and http://www.codeproject.com/dotnet/DotNetComPorts.asp[^]

PeterRitchie.com

Exception handling problem..

23-Apr-05 13:51

myCommand = new SqlCommand("INSERT INTO CES VALUES('"+(textBox1.Text)+"',"+
(textBox2.Text)+",'"+
(textBox3.Text)+"',"+
(textBox4.Text)+",'"+
(textBox5.Text)+
"','"+(textBox6.Text)+"','"+
(comboBox1.Text)+"',"+
(comboBox2.Text)+","+
(comboBox3.Text)+","+
(comboBox4.Text)+")"
,Form1.myConnection);

The problem is when I executed it , sometimes it throws an exception because of parameter missmatch...What I want is , I want to know which part of the command throws that exception.. Does anyone has any idea how to locate it?
Why I want is :
for example , if textBox1 has the problem the user can correct the wrong value of the field without entering all the values the other fields has..

Re: Exception handling problem..

Carl Mercier23-Apr-05 14:03

Carl Mercier

23-Apr-05 14:03

The way you do it is just plain bad.

What if the user types in a value that contains an '??? It will crash right away. You need some validation. You should also make use of SqlParameter.

Re: Exception handling problem..

Tugbay Sahin23-Apr-05 14:55

Tugbay Sahin

23-Apr-05 14:55

I have some validations...It is not the problem for me.. The code is just an example..

Re: Exception handling problem..

Carl Mercier23-Apr-05 16:43

Carl Mercier

23-Apr-05 16:43

Ok.

Use SqlParameter, it is much more efficient than adding all the values to a string. It should solve your problem.

Re: Exception handling problem..

Dave Kreskowiak23-Apr-05 17:31

Dave Kreskowiak

23-Apr-05 17:31

Then demonstrate how to do it the right way. Use the SqlParameter class. It'll take care of escaping the things that need to be, defend against a good number of SQL injection attacks and also makes it easier to find out where your problem is.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Re: Exception handling problem..

Colin Angus Mackay23-Apr-05 22:48

Colin Angus Mackay

23-Apr-05 22:48

Tuğbay wrote:
I have some validations...It is not the problem for me..

You should use parameterised queries as a matter of course. Injecting values into a SQL String like this is not acceptable in today's security aware world.

See this article[^] which explains the security issues with the way you are doing this and gives an example of moving from this injection based way to using parameterised queries.

As a general bit of advice. If you are getting a syntax error and you need help on a forum you need to post the exact code that caused the syntax error and the syntax error itself. In this case you need to post the result of the string concatenations as it is quite difficult to tell from just the C# code alone.

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