A simple function pointer question... - C# Discussion Boards

Stephane Rodriguez.9-Nov-02 9:25

9-Nov-02 9:25

Anonymous wrote:
Is there any adavantage of using begininvoke/endinvoke?

I am afraid not since that's what is done already. By the way, you should also know that the underlying connection is multi-threaded too (with an upperbound I can't remember at the moment).
I believe the only way to cope with the problem you are facing is to write your own httpweb request stuff. The funny thing is the http web request itself is bad only because it doesn't provide configuration capabilities over the underlying connection. There is a lot of application logic underneath.
Which is equivalent to say the people at MS who created it thought developers were ready to do web requesting on a fire and forget basis. That's a stupid assumption of course...

Back to real work : D-21.

Again dialog ... :(

Karavaev Denis9-Nov-02 5:29

Karavaev Denis

9-Nov-02 5:29

Ok, thanks everyone, but I have one more question.
To gett callback of my modal dialog I use this code:

ModalDlgClass myDlg = new ModalDlgClass();
if(myDlg.ShowDialog() == DialogResult.OK)
{
//Do smf.
}

But in the modal dialog there is a small problem ...
I need to check something before close it.

if(textBox1.Text.Length == 0)
{
//cheking and need returf focus to modal dialog
}
else
{
//do smf else, then
this.Close(); // I need 2 close it ONLY if textBox1 is not emty
}

But if my textBox1 is empty after checking modal dialog is closing ... is there any way not to close it?

thanks

=====================
http://wasp.elcat.kg

Re: Well...

Masaaki Onishi10-Nov-02 7:15

Masaaki Onishi

10-Nov-02 7:15

Hello, the codegurus around the world.;)

If you work for MFC, you will figure it out.
Maybe, you just declare MyDialog_OnClose message method, and filter
the textbox input.
And, if there is no input, just return before the base class Close is called.
Just put "return".
I believe that this works.

Please, don't send me your email about your questions directly.
Have a nice day!
Sonork - 100.10571:vcdeveloper Wink | ;)

-Masaaki Onishi-

Re: Well...

Karavaev Denis10-Nov-02 16:36

Karavaev Denis

10-Nov-02 16:36

I deed, but it, not working.
I have modal dialog. And it's closing even if i put 'return'.
Maybe it is becourse I click on button with 'OK' dialog properties?
But is it only way to get response from my Modal dialog?

=====================
http://wasp.elcat.kg

Re: Ooops.

Masaaki Onishi10-Nov-02 17:29

Masaaki Onishi

10-Nov-02 17:29

Hello, the codegurus around the world.;)

Oooops, you're right because I got the same result.
So, I asked "HELP" of VC#.

1) Use DialogResult.NONE

protected void btnOK_Click (object sender, System.EventArgs e)
{
        // OK button clicked.
	// get new message.
	strMessage = txtMessage.Text;

	if(strMessage == "") 
	{
		MessageBox.Show(this, "Error");
		DialogResult = DialogResult.None;
	}
}

2) Disable OK button if TextBox is empty

private void Msg_TextChanged(object sender, System.EventArgs e)
{
   if(txtMessage.Text == "")
	btnOK.Enabled = false;
   else
	btnOK.Enabled = true;
}

Please, don't send me your email about your questions directly.
Have a nice day!
Sonork - 100.10571:vcdeveloper Wink | ;)

-Masaaki Onishi-

Re: Ooops.

Karavaev Denis11-Nov-02 2:36

Karavaev Denis

11-Nov-02 2:36

Yah!!! thanks,

Nice idea to lock button till text is empty! Wink | ;)

=====================
http://wasp.elcat.kg

Re: Again dialog ... :(

mikasa11-Nov-02 6:52

mikasa

11-Nov-02 6:52

I had to do this in VB.NET. What I did was I didn't "HardCode" the "Dialog Result Codes" into my Command Buttons. When the User clicked the "Login" Button of my Form, I would Validate the Login info, if it was Correct, I would just Type "Return DialogResult.OK", otherwise I would not return anything.

A simple function pointer question...

Dave Kerr9-Nov-02 0:40

Dave Kerr

9-Nov-02 0:40

Hi I'm havinh real trouble using this one OpenGL function I'm trying to import into my app. The C function is declared as this:-

void gluTessCallback(GLUtesselator* obj, GLenum type, void(*fn)());

I know that GLUtesselator* is basically just an IntPtr, as I've imported other functions with it in, and they've worked fine. Similarly, GLenum is just a UInt. But what do I do with the void function pointer?
I have declared delegates for all of the possible function types it could be, (depending on the 'type' variable), but I don't know where to go from there.

MSDN only has info for function pointers that are always a set type, but with this function, the pointer can be to a number of different types of function.

Please help me out here!

Thanks in advance
Dave

Dave Kerr
focus_business@hotmail.com
www.focus.esmartweb.com

Re: A simple function pointer question...

beetung9-Nov-02 1:13

beetung

9-Nov-02 1:13

Dave Kerr wrote:
declared as this:-

void gluTessCallback(GLUtesselator* obj, GLenum type, void(*fn)());

....
I don't know where to go from there.

Is C# really that much different from C++??

//declaring three variables
GLUtesselator* gPtr =...;
        GLenum gType =...;
        void(* gFuncPtr  )(void);
        gFuncPtr = ...;

// call the function
gluTessCallback(gPtr, gType, gFuncPtr);

wont compile under C#??

Re: A simple function pointer question...

Stephane Rodriguez.9-Nov-02 2:50

Stephane Rodriguez.

9-Nov-02 2:50

Did you give a look at this[^] ?

To ease the marshaller's job, you may also add this attribute : [MarshalAs(UnmanagedType.FunctionPtr)]

Back to real work : D-21.

MDI application

Le centriste8-Nov-02 17:43

Le centriste

8-Nov-02 17:43

is it possible to build an MDI application in C#, especially using VS.NET?

Michel

It is a lovely language, but it takes a very long time to say anything in it, because we do not say anything in it, unless it is worth taking a very long time to say, and to listen to.

- TreeBeard

Re: MDI application

Stephane Rodriguez.8-Nov-02 19:37

Stephane Rodriguez.

8-Nov-02 19:37

You've got a MDI sample written in C# in your .NET framework samples : SDK\Samples\Quickstart\Winforms\samples\mdi.

Back to real work : D-21.

Re: MDI application

Le centriste9-Nov-02 7:33

Le centriste

9-Nov-02 7:33

Tx. but I found this in MSDN

ms-help://MS.VSCC/MS.MSDNVS/vbcon/html/vbconMDIApplications.htm[^]

NOTE: You must have MSDN installed to follow this link. If not:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vbcon/html/vbconmdiapplications.asp[^]

Michel

It is a lovely language, but it takes a very long time to say anything in it, because we do not say anything in it, unless it is worth taking a very long time to say, and to listen to.

- TreeBeard

Re: MDI application

Eric Gunnerson (msft)11-Nov-02 7:44

Eric Gunnerson (msft)

11-Nov-02 7:44

If you go to http://www.csharp.net, in the 'Code' section there's a library that I think does this. IIRC, it's called Genghis.

FileSize

kavehdr8-Nov-02 12:08

kavehdr

8-Nov-02 12:08

Hi, Does anyone know here how to make a file with C# that has a wrong size. Say 10TB, but a single file that actually only takes a few bytes on the drive?

Thanks

K.D.

Re: FileSize

ian mariano8-Nov-02 20:03

ian mariano

8-Nov-02 20:03

You can see if a file or directory is a Sparse File[^] in c# by examining the file attributes.

Using win32 and unmanaged code, you'd mark a file / dir as sparse using DeviceIoControl passing in FSCTL_SET_SPARSE as the i/o control mode, that is, after you've confirmed the file system supports sparse files. FSCTL_SET_SPARSE[^].

There doesn't appear to be a managed version.

"The greatest danger to humanity is humanity without an open mind."
- Ian Mariano - http://www.ian-space.com/

C# determinism

AaronStibich8-Nov-02 12:03

AaronStibich

8-Nov-02 12:03

I have been reading alot about C# determinism, and most of the literature addresses destructors. I understand that the garbage collection is now responsible for calling the class destructor, and the GC is undeterministic. I have read recommendations to implement IDispose and have the client call Dispose(), but what about client server architectures. If I have one C# server connected to multiple clients, which client calls Dispose()? Isn't this why reference counting was invented?

My biggest concern is whether or not my C# server will contain a message pump - someone alluded earlier that it will. Anyone who has created a COM STA server will know that message pumps make your code slow and VERY undeterministic. How to you create a message pump free C# server (something equivilent to a MTA server in COM)?

Thanks,

Aaron

Aaarrrgggghhh what have I done???

LongRange.Shooter8-Nov-02 9:24

LongRange.Shooter

8-Nov-02 9:24

I created a Windows Application project in C#.
I created a number of forms that are inherited forms.

If I keep the original form in the project, I can only set that form as the Startup object, and it goes without saying that if I remove it, I cannot set anything to the Startup object. (compile says myNamespace.formname does not exist if I manually enter the inherited form name)

Why can't I set an inherited form as a Startup object and how do I get around this???? Even if I add a normal form (not inherited) after my inherited forms it does not allow me to set even that normal form now. In fact, I get no dropdown box in the StartObject property of the project!!!!!

Confused | :confused:

_____________________________________________
_{I have a tendancy to where my mind on my sleeve
I have a habit of losing my shirt...}

Re: Aaarrrgggghhh what have I done???

LongRange.Shooter8-Nov-02 9:41

LongRange.Shooter

8-Nov-02 9:41

Never mind. I found my problem....I have to add the following section to my code manually:

<br />
		[STAThread]<br />
		static void Main() <br />
		{<br />
			Application.Run(new myForm());<br />
		}<br />

_____________________________________________
_{I have a tendancy to where my mind on my sleeve
I have a habit of losing my shirt...}

Hashtable

afronaut8-Nov-02 6:57

afronaut

8-Nov-02 6:57

In a C# hash is it possible to get an item by its key and to get a key by a value? Something like this:

myhash.Add("David","C#")
myhash.Add("Chris","Perl")

?myhash.Items("David") -- should be C#
?myhash.Keys("Perl") -- should be Chris

What is the correct syntax?

sigh, the things you do for date/times.

*->>Always working on my game, teach me
*->>something new.
cout << "dav1d\n";

Re: Hashtable

perlmunger8-Nov-02 7:19

perlmunger

8-Nov-02 7:19

Add a key value pair:

myhas["David"] = "C#";

Get a key by it's value:

string item1 = myhash["David"]

Iterate through all items:

foreach( string key in myhash.Keys )
{
  // 1st iteration key holds "David"
  string item1 = myhash[key];
  // item1 now holds "C#"
}

Determine if hashtable contains a particular key:

if( myhash.Contains("David") )
{
  // do something
}

Determine if hashtable contains a particular value:

if( myhash.ContainsValue("C#") )
{
  // do something
}

In general you won't want to look up a key by it's value since keys are (usually) unique, but values aren't. Does this help?

-Matt

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

The 3 great virtues of a programmer:
Laziness, Impatience, and Hubris.
--Larry Wall

Re: Hashtable

afronaut8-Nov-02 8:51

afronaut

8-Nov-02 8:51

Thanks Matt -

I needed to have a hashtable of months of the year:
"January","1"
"February","2"
...
and be able to get a month based on a numeric index OR an index based on a month string.
I thought it would be easy with a Hashtable but you're right - it doesn't support lookups by value assuming you could have multiple 'values' with different keys. But there are a lot of cases like this where I know there is a one to one mapping of name/value pairs. Items that are always used in association and are unique.

I used a simple array and wrote a finder method that looked like this:

<br />
string[] months = {"Jan","Feb","Mar",...}<br />
<br />
		private int GetMonthIndex(string mo){<br />
			for(int i=0;i<mos.Length;i++){<br />
				if(mos[i]==mo)return i+1;<br />
			}<br />
			return -1; // <-- if it doesn't pan out...<br />
		}<br />

Incidentally I asked my perl jedi master and he must have been laughing when he wrote this:

<br />
$hash{'David'} = 'C#';<br />
$hash{'Chris'} = 'Perl';<br />
@keys = grep { $hash{$_} eq 'Perl' } keys %hash;  #perl is s1ck<br />

In the end, while I didn't change my use of a simple array and a brutally slow sequential search, I wrote this for future reference:

<br />
		public static string GrepHashForKey(Hashtable ha, string search){<br />
			foreach(object o in ha.Keys){<br />
				if(ha[o].ToString().Equals(search))<br />
					return o.ToString();<br />
			}<br />
			return "";<br />
		}<br />

*->>Always working on my game, teach me
*->>something new.
cout << "dav1d\n";

Re: Hashtable

perlmunger8-Nov-02 9:22

perlmunger

8-Nov-02 9:22

Just use an ArrayList. Just make sure you add the months to the ArrayList in the right order. Like this:

ArrayList months = new ArrayList();
months.Add("January");
months.Add("February");
// .... etc

int monthNum = months.IndexOf("January") + 1; 
// +1 to account for the zero-based index.

string monthName = months[monthNum - 1];
// -1 to account for the zero-based index.

That should do it eh?

-Matt

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

The 3 great virtues of a programmer:
Laziness, Impatience, and Hubris.
--Larry Wall

Re: Hashtable

afronaut8-Nov-02 9:52

afronaut

8-Nov-02 9:52

A two liner for my woes! Humbling but good to know -

Thanks Matt.

*->>Always working on my game, teach me
*->>something new.
cout << "dav1d\n";

Re: Hashtable

leppie8-Nov-02 12:48

leppie

8-Nov-02 12:48

afronaut wrote:
I needed to have a hashtable of months of the year:
"January","1"
"February","2"
...
and be able to get a month based on a numeric index OR an index based on a month string.

static string PrintMonth(int i)
{
   return new DateTime(0).AddMonths(i).ToString("MMMM");
}

static int PrintMonthNr(string month)
{
   for (int i = 0; i < 12; i++) 
   {
      if (PrintMonth(i) == month) return i;
   }
   return -1;//some impossiblerroroccured
}

"I dont have a life, I have a program."

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