C# Discussion Boards - CodeProject

Profox Jase21-Feb-02 9:38

21-Feb-02 9:38

Thanks for the advice. I will try to figure out how to make an asynchronous call - I assume this would be different to the flags that Jerzy is talking about?

Thanks though, will look into it.

Jase

Jason King

jason.king@profox.co.uk
Feel the love at www.profox.co.uk

Peter Stephens21-Feb-02 9:56

Peter Stephens

21-Feb-02 9:56

Asynchronous calls in .NET use delegates. There are methods on a delegate called BeginInvoke and EndInvoke. I personally have not used async calls yet, but plan to do so soon. Smile | :)

AFAIK .NET async calls use a threadpool behind the scenes.

--
Peter Stephens

Profox Jase21-Feb-02 9:36

21-Feb-02 9:36

Thanks alot, that's a whole lot of detail. The example clinches it. You are the man Cool | :cool:

.

Cheers
J;)

Jason King

jason.king@profox.co.uk
Feel the love at www.profox.co.uk

Profox Jase22-Feb-02 0:37

22-Feb-02 0:37

Hey Jerzy,

I tried this, but for some reason, none of the flags I pass in seem to make any difference. The sound does play though. Also, for some reason, when I use the enums as per your example, the code won't compile. I have tried subsituting the enums in the example for their values, but still things don't go according to my expectation (ie, makes no difference).

Does this declaration look right for c# to you?

public static extern long PlaySound(String lpszName, long hModule, long dwFlags);

As far as I understand it, my alternatives are:

1. no sound at all
2. use a com object as per my original fox pro code
3. for every sound played, create a new thread, play the sound, kill the thread
4. do some asynch calls with beginInvoke and delegates and stuff.

Don't want to do 1., 2. seems a good thing to learn in c#, in fact as does 3 and 4.

4 however I will have to leave until I have learnt a whole lot more or until someone explains the whole delegate thing to me.

If you have any more suggestions along the lines of your original, or anything else for that matter, would love to hear 'em.

Jase

Jason King

jason.king@profox.co.uk
Feel the love at www.profox.co.uk

22-Feb-02 3:35

I tested this code and it's working:

....
....
....
using System.Runtime.InteropServices;

public class Form1 : System.Windows.Forms.Form
{
public enum PlaySoundFlag
{
Synchronously = 0x0000,
Asynchronously = 0x0001,
NoDefault = 0x0002,
Memory = 0x0004,
Loop = 0x0008,
NoStop = 0x0010,
NoWait = 0x00002000,
Alias = 0x00010000,
AliasId = 0x00110000,
Filename = 0x00020000,
Resource = 0x00040004,
Purge = 0x0040,
Application = 0x0080
}

[DllImport("winmm.dll")]
public static extern int PlaySound(String pszSound, int hmod,PlaySoundFlag fdwSound);

public Form1()
{
....
....
....

PlayTest();

....
....
....
}

void PlayTest()
{
PlaySound("c:\\windows\\media\\Windows XP Startup.wav", 0,
PlaySoundFlag.Filename|PlaySoundFlag.Asynchronously);
}

Jerzy

Peter Stephens22-Feb-02 7:48

Peter Stephens

22-Feb-02 7:48

Profox Jase wrote:
public static extern long PlaySound(String lpszName, long hModule, long dwFlags);

Your problem is the long type. In C# this is a 64 bit int. You should use int instead.

--
Peter Stephens

Profox Jase25-Feb-02 5:25

DropDownList in C# Application

25-Feb-02 5:25

Cool, thanks again.

J

Jason King

jason.king@profox.co.uk
Feel the love at www.profox.co.uk

Gavin_Mannion20-Feb-02 23:10

Gavin_Mannion

20-Feb-02 23:10

Hi All,

I have a form which has a dropdown list on it which is being populated by an array. What I am trying to find out how to do is set a value for a option in the dropdown list so that I can query the database using a Integer and not a text field.

Example: Smile | :)

My Drop Down list has the following
Option 1: London
Option 2: Liverpool
Option 3: Other

If my user selects 'Liverpool' I would like to get the value '42' which is the unique ID in the database that is connected to Liverpool.

In ASP and VB you where just able to add a value to the field, can this be done in C#?

Thanks,

Christopher Lord20-Feb-02 23:38

Christopher Lord

20-Feb-02 23:38

If your working in ASP.net, one of the the Add overrides lets you specify a ListItem class, which takes two strings. These map to the text of the option and the value of the option in html. Value can be retrieved from SelectedItem.Value, and the text from SelectedItem.Text.

I expect C# for apps is fairly close, but there are definately differences between the two. One difference I expect is the ability to map an object to the string instead of a second string.

// Rock

Gavin_Mannion21-Feb-02 0:50

Gavin_Mannion

21-Feb-02 0:50

Using ASP I have been able to do it and that is why I expect it to be at least similar in a C# Application. There just doesn't seem to be a possible option for value which is mind boggling if they have decided to scrap that one.

Please let me know if you come across anything that explains this, also how do you mean
CLaW wrote:
One difference I expect is the ability to map an object to the string instead of a second string. ????

Thanks

SimonS21-Feb-02 22:45

SimonS

21-Feb-02 22:45

Hi Gavin

The ComboBox in .NET receives a generic object. This is pretty powerful, but also is quite a change to the normal VB-style. All that's required is to create a simple (or more complex) class and use that to add to the ComboBox.

To get values out, just cast to your object and call your custom props. The ToString() override caught me out, but the ComboBOx uses it to show values.

private void Form1_Load(object sender, System.EventArgs e)
{
comboBox1.Items.Clear();
comboBox1.Items.Add(new cComboLoader("Bill",1));
comboBox1.Items.Add(new cComboLoader("Steve",2));
comboBox1.Items.Add(new cComboLoader("Paul",3));
comboBox1.Items.Add(new cComboLoader("Reinout",4));

}

private void button1_Click(object sender, System.EventArgs e)
{
MessageBox.Show(((cComboLoader)comboBox1.SelectedItem).ToString());
MessageBox.Show(((cComboLoader)comboBox1.SelectedItem).myIndexVal().ToString());
}

public class cComboLoader
{
private string _Txt="";
private int _iVal=0;
public cComboLoader(string sTxt, int iVal)
{
_Txt=sTxt;
_iVal=iVal;
}
public override string ToString()
{
return _Txt;
}
public int myIndexVal()
{
return _iVal;
}
}

Does this help you?

Cheers,
Simon

X-5 452 rules.

Gavin_Mannion21-Feb-02 22:53

Gavin_Mannion

21-Feb-02 22:53

Wow, just a little bit more complicated than VB Smile | :)

...

Well that is exactly what I was looking for but as usual it has arrived about 2 hours after I came up with another solution. I will keep it in my code bank though because it is most probably better than mine Smile | :)

..

What I have done is load a 2 dimensional array with the ID's and strings, then loaded the combobox with the string. When a option is chosen it loops through my Array to find the matching ID.

Hey it works Poke tongue | ;-P

Thanks for the help though

SimonS21-Feb-02 22:59

SimonS

21-Feb-02 22:59

You can easily combine the 2 solutions by using the temp. inline cComboLoader class in your Combo.Items.Add.

What will happen if you get 2 values with the same text, but diff. ID's?

Cheers,
Simon

X-5 452 rules.

How to Map a C++ Struct from a DLL into C#

James T. Johnson22-Feb-02 7:29

James T. Johnson

22-Feb-02 7:29

There is another way, it involves using the DataSource, DisplayMember and ValueMember properties of the combo box. If I weren't late for work I'd describe exactly how to use it, but if you search the docs for DisplayMember there is an example of using it Smile | :)

James

Sonork ID: 100.11138 - Hasaki
"My words but a whisper -- your deafness a SHOUT.
I may make you feel but I can't make you think." - Thick as a Brick, Jethro Tull 1972

Setting a timeout

20-Feb-02 19:36

Hi,

I have a Socket which is binded to a local UDP endpoint. When recieving data using the Recieve() funtion, the host may timeout and my program just sits there.

Any idea on how to set a timeout ? I remember java having a method to do it which throws an exception if the timeout occours.

Any ideas people ?

Cheers

Felix Nielsen20-Feb-02 11:44

Felix Nielsen

20-Feb-02 11:44

Hi
I am using a DLL, where one of the functions need a pointer to a C/C++ struct, here is the struct :

struct Transaction {
char card_number[21];
int card_expirymonth;
int card_expiryyear;
}

So I need to be able to declare the struct in C#, and pass a pointer from the C# "struct/class" to the DLL funcion. Of cause the sizeof should be the same. I hope it can be done Smile | :)

Thanks
Felix Smile | :)

20-Feb-02 14:48

When you have a struct of simple datatypes creating the struct should be fairly easy.

[StructLayout(LayoutKind.Seqential)]
public struct Transaction {
  [MarshalAs(UnmanagedType.LPStr, SizeConst=21)] string card_number;
  [MarshalAs(UnmanagedType.U4)] int card_expirymonth;
  [MarshalAs(UnmanagedType.U4)] int card_expiryyear;
}

Of course this is untested code, but I believe that is correct attributes used.

HTH,

James

Sonork ID: 100.11138 - Hasaki
"My words but a whisper -- your deafness a SHOUT.
I may make you feel but I can't make you think." - Thick as a Brick, Jethro Tull 1972

20-Feb-02 22:15

Hi James,

THX - I'll try that Smile | :)

, btw. is it possible to use the sizeof() function on the struct?

Felix

Filip21-Feb-02 3:32

Filip

21-Feb-02 3:32

I have the same problem

i have to pass a pointer to the DOC_INFO_1 structure via the winapi
StartDocPrinter(handle, data, *DOC_INFO_1)

DOC_INFO_1
{
LPTSTR pdocname
LPTSTR pdatatype
LPTSTR poutputfile
}

can anyone help me?

James T. Johnson21-Feb-02 19:56

James T. Johnson

21-Feb-02 19:56

Oops, I think there is an error in what I suggested trying.

[StructLayout(LayoutKind.Seqential, CharSet=CharSet.Ansi)]
public struct Transaction {
  [MarshalAs(UnmanagedType.ByValTStr, SizeConst=21)] public string card_number;
  [MarshalAs(UnmanagedType.U4)] public int card_expirymonth;
  [MarshalAs(UnmanagedType.U4)] public int card_expiryyear;
}

What I told you the first time would have been correct if card_number were a pointer to a char* and not an array in the struct.

Sorry about that,

James

Sonork ID: 100.11138 - Hasaki
"My words but a whisper -- your deafness a SHOUT.
I may make you feel but I can't make you think." - Thick as a Brick, Jethro Tull 1972

Felix Nielsen21-Feb-02 23:01

Felix Nielsen

21-Feb-02 23:01

Hi James,

Thanks, I did some testing Yesterday, and it did'nt work, when I passed the struct to the DLL, it got a the pointer to "card_number", and the DLL was unable to fetch the other fields.

Felix

Felix Nielsen22-Feb-02 11:26

Felix Nielsen

22-Feb-02 11:26

Hi James,

It seems to working as a CHARM Smile | :)

Thanks again Smile | :)

Felix