How do you create an object from a C++ DLL in C# - C# Discussion Boards

Changing value of all TextBoxes

24-Feb-02 11:43

Thanks, James, for the link to those two DotNet mailing lists. I'm already signed up! Big Grin | :-D

--
Peter Stephens

Gavin_Mannion21-Feb-02 22:59

21-Feb-02 22:59

Hi All,

Simple question here (I Hope)

I need to reset all my textboxes back to blank and am trying to do it in a nice clean loop.

I have the following but it does not work

foreach (TextBox t in this)
{
	t.Text = "";
}

I am getting the error message

C:\Documents and Settings\gavin\My Documents\Visual Studio Projects\LTBRMaintenance\EditClinic.cs(487): foreach statement cannot operate on variables of type 'LTBRMaintenance.EditClinic' because 'LTBRMaintenance.EditClinic' does not contain a definition for 'GetEnumerator', or it is inaccessible

I have a feeling I am nearly there but am missing something obvious..

Thanks

SimonS21-Feb-02 23:07

21-Feb-02 23:07

I think that this is just an object and doesn't natively expose a GetEnumerator method. Try this:

foreach(Control c in this.Controls)
{

if(c.GetType().ToString()=="System.Windows.Forms.TextBox")
c.Text="new vlaue";

}

Cheers,
Simon

X-5 452 rules.

Gavin_Mannion21-Feb-02 23:26

21-Feb-02 23:26

That is exactly it.

Smile | :)

Thanks

James T. Johnson22-Feb-02 7:27

James T. Johnson

22-Feb-02 7:27

simons wrote:
if(c.GetType().ToString()=="System.Windows.Forms.TextBox")

You could also use; if( c is System.Windows.Forms.TextBox ) this lets the value change for controls derived from TextBox too 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

SimonS25-Feb-02 0:14

How to Chnage the Default Select bgcolor of the TreeView item

25-Feb-02 0:14

James T. Johnson wrote:
if( c is System.Windows.Forms.TextBox )

That's a better way. Probably more robust too (if MS changes the text of class names).

Cheers,
Simon

X-5 452 rules.

Welson21-Feb-02 16:05

Welson

21-Feb-02 16:05

I would like to set owner bgcolor while the user select an item in the treeview.
how do i do the work Confused | :confused:

How do you create an object from a C++ DLL in C#

21-Feb-02 14:05

Hi,

I have a c++ DLL it contains a class called MyClass with methods GetName and SetName.

[DllImport("MyClass.dll")]
public static extern void GetName( string name);

This doesn't work because I need to instanciate the class.

How do I declare the class and methods within the class?

Then how do I instancial the class and call the method?

Thanks

Mike

Re: How do you create an object from a C++ DLL in C#

Nemanja Trifunovic21-Feb-02 14:52

Nemanja Trifunovic

21-Feb-02 14:52

No way to do this from C#. Either use MC++, or wrap your class into a COM object and the reference it from your code.

I vote pro drink Beer | [beer]

Playing sounds through c#

Profox Jase21-Feb-02 4:57

21-Feb-02 4:57

Hello helpers.

So far, my asteroids game is coming along nicely, and I am learning lots. Now has come the time to get c# to play some sounds - by searching around I have found this:

[DllImport("winmm.dll")]
public static extern long PlaySound(String lpszName, long hModule, long dwFlags);

This does is fact work, however, the keener amongst you will realise that code execution stops until this function returns a value. Of course, in my game, I don't want the game to freeze everytime I call this function, so, is there
a) another method for playing a sound file (I used a com object in Foxpro) and if so, can somebody tell me how to do it in C#
b) a way to call PlaySound without waiting for a return value?

Many thanks you gorgeous hamsters
Confused | :confused:

J

Jason King

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

21-Feb-02 7:22

Use ASYNC flag that has a value 0x0001.

You can use enum to include other flags:

public enum PlaySoundFlag
{
// Play synchronously (default)
Synchronously = 0x0000,

// Play asynchronously
Asynchronously = 0x0001,

// Silence (!default) if sound not found
NoDefault = 0x0002,

// pszSound points to a memory file
Memory = 0x0004,

// Loop the sound until next sndPlaySound
Loop = 0x0008,

// Don't stop any currently playing sound
NoStop = 0x0010,

// Don't wait if the driver is busy
NoWait = 0x00002000,

// Name is a registry alias
Alias = 0x00010000,

// Alias is a predefined ID
AliasId = 0x00110000,

// Name is file name
Filename = 0x00020000,

// name is resource name or atom
Resource = 0x00040004,

// Purge non-static events for task
Purge = 0x0040,

// Look for application specific association
Application = 0x0080
}

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

Should work

Jerzy

Peter Stephens21-Feb-02 7:42

21-Feb-02 7:42

Or you could use an Asynchronous method call or make your synchronous call on a different thread.

--
Peter Stephens

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

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

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

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

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

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

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