Re: C# and mysql - C# Discussion Boards

Re: system.array as parameter

26-Oct-05 15:00

try object[]

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Member 239309226-Oct-05 15:12

Member 2393092

26-Oct-05 15:12

thanks for the prompt response.
I did, with not much success.
anyone has an idea ?

Re: system.array as parameter

leppie26-Oct-05 15:26

26-Oct-05 15:26

Seeing its an out parameter, try this:

Array input;
Foo(out input);
MyType[] rinput = input as MyType[];

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C# and mysql

vandread126-Oct-05 13:51

vandread1

26-Oct-05 13:51

I need help trying to open up a mysql database using Visual C#.

Christian Graus26-Oct-05 13:55

Christian Graus

26-Oct-05 13:55

What have you already tried ? Google ? Searching this site ?

Christian Graus - Microsoft MVP - C++

Wjousts26-Oct-05 14:50

26-Oct-05 14:50

There's a very nice MySql Connector for .NET on the MySql.org website.

seee sharp26-Oct-05 18:21

seee sharp

26-Oct-05 18:21

http://www.codeproject.com/cs/database/AbdMySqlSchema.asp[^]

Smile | :)

- ashish

Jeason Zhao27-Oct-05 4:26

Jeason Zhao

27-Oct-05 4:26

Ado.Net2.0 can enum most of metadata from database

Please pardon my weak English!

vandread12-Nov-05 8:12

vandread1

2-Nov-05 8:12

I am unable to see the source code for the first link that you provided. Are there any other suggestions or source code that anyone can provide me with?

C# ArrayList

Doncp26-Oct-05 12:38

Doncp

26-Oct-05 12:38

I am trying to add an instantated class (which is an Object - I hope!) to an Arraylist every time the data in the class changes. This instantated object is composed of several other instantated classes (objects).

Example:
ArrayList myObj = new ArrayList();

class foo;
foo.strName = "name";
myObj.Add(foo);

...

foo.strName = "newname";
myObj.Add(foo);

When I look (via QuickWatch) at the Arraylist elements, they all appear to be the same, i.e.,
myObj[0] foo.strName == "newname" &&
myObj[1] foo.strName == "newname".

Yet, I know the data in the class has changed.

Am I doing something that is invalid? What am I doing wrong?

Thanks Confused | :confused:

Wjousts26-Oct-05 12:48

26-Oct-05 12:48

You need to instantate a new object every time. If you just change a member of the object you still have the same object it doesn't automagically create a new object and it'll still be the same object that is already in your ArrayList.

enjoycrack26-Oct-05 12:49

enjoycrack

26-Oct-05 12:49

hi there,

it sounds to me that u are adding only one object to array list.
and actually the reference to the object stored in the arraylist. So whenever u change it's attribute, all objectes in the arraylist will take affect, I think.
So the code should be:
class foo = new cfoo();
foo.strName="name";
obj.Add(foo);

....
foo = new cfoo();
...
obj.Add(foo);

Try it

<< >>

Edbert P26-Oct-05 12:57

Edbert P

26-Oct-05 12:57

In your code, you did not instantiate a new foo object, instead you are modifying the foo.strName only.
An ArrayList stores reference to your object, therefore if you store two reference to the same object they will result in the same object.

Try this instead:

ArrayList myObj = new ArrayList();

ClassName foo = new ClassName(); //Or however you instantiate a new foo object
foo.strName = "name";
myObj.Add(foo);

...

foo = new ClassName();           //Instantiate a new class with the same object name (foo)
foo.strName = "newname";
myObj.Add(foo);

This will result in two different objects which references are contained in your myObj ArrayList.
Does that help?

Edbert P.
Sydney, Australia

-- modified at 18:58 Wednesday 26th October, 2005

Doncp27-Oct-05 6:01

Doncp

27-Oct-05 6:01

Thanks to All,

My problem was not quite as simple as I showed in my example (i.e., I have multiple embedded classes involved), but all of you put me on the right track. I didn't realize that a reference to my class was what was put into the Arraylist.

I am able to do what I originally wanted, but had to do it a different way.

Thanks

Don D'Oh! | :doh:

P/Invoke problem

Mark Tutt26-Oct-05 12:19

Mark Tutt

26-Oct-05 12:19

After a day of scratching my head, I think I've found the problem with my latest project, however I'm not sure what to do about it.

I've wrapped a legacy DLL with a .NET remoting solution that allows the functions to be accessed easily from ASP.NET. The DLL is used for reporting.

On my test system, with demo configuration and minimal data, everything worked fine.

At the clients site, where the reports are larger, the remoting service returns a null reference exception when the reports are over 4k.

Here is functions P/Invoke signature:

[DllImport("opsrpts.dll", CallingConvention=CallingConvention.Cdecl)]
static extern String DisplayReport(int rvc, int wsobj, int rptnum, int period, int scope, int reset, int range, int start, int end, int suppress);

and the C declaration:

extern "C" DLLIMP_DBI char* __cdecl DisplayReport(int rvc, int wsobj, int rptnum, int period, int scope, int reset, int range, int start, int end, int suppress)

I'm assuming that the attempt to append more than 4k in a single string operation blows something up somewhere. At this point it's the only logical explaination I have.

Is there any way other than modifying the report to get the larger reports back? Since there is no way to just take the char* and work with it, I can't think of a way other than changing the DLL to use multiple calls to pull the data back in chunks.

Thanks in advance!

Re: P/Invoke problem

leppie26-Oct-05 12:59

26-Oct-05 12:59

Mark Tutt wrote:
char* __cdecl DisplayReport

Shoot the person that wrote that function, shoot him dead. People like that should not be allowed behind a keyboard. Suggest to him in a nice way that he should join the police academy.

Alternatively if you run out of bullets, or dont have any handy, try the StringBuilder class instead.

The correct way would be to get the value for that char*, then do Marshal.PtrToString, then pray the person that wrote the DLL used the default malloc/free mechanism. PInvoke free() passing the char* to prevent memory leaks.

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Re: P/Invoke problem

Mark Tutt26-Oct-05 13:22

Mark Tutt

26-Oct-05 13:22

leppie wrote:
Shoot the person that wrote that function, shoot him dead. People like that should not be allowed behind a keyboard. Suggest to him in a nice way that he should join the police academy.

Alternatively if you run out of bullets, or dont have any handy, try the StringBuilder class instead.

Now now, the DLL in question is part of a legacy codebase that goes back nearly 15 years, and is pretty much exclusively C/ASM. Gotta give a little respect to the people who wrote the stuff that the world runs on.

I'll take a look at Marshal.PtrToString...

Re: P/Invoke problem

leppie26-Oct-05 13:31

Calling dynamicly created buttons

26-Oct-05 13:31

Mark Tutt wrote:
pretty much exclusively C/ASM.

Even for C that is bad.

Mark Tutt wrote:
Gotta give a little respect to the people who wrote the stuff that the world runs on.

Now I'm getting more worried... Sigh | :sigh:

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mwallon26-Oct-05 12:17

mwallon

26-Oct-05 12:17

Hi all, I'm new to this forum and to c# and my first project is a simple calendar for my tablet pc. In this project I dynamicly create buttons based on current month, looks like this:
private void createButtons()
{
int xet;
int numFirstDay;
DateTime myDateTime = new DateTime(activeYear,activeMonth,1);
if(myDateTime.DayOfWeek==DayOfWeek.Monday)
{
//functions for checking witch day in week the first day is }
int yet=569; int numdays =
DateTime.DaysInMonth(activeYear,activeMonth);
for(int i=1; i350)
{
yet+=20;
xet=16;
}
p.Y=yet;
p.X=xet;
aButton.Location=p;
aButton.Width=50;
aButton.Height=20;
aButton.Tag=i;
aButton.Name="button"+i;
aButton.Text=i.ToString();
if(i==activeDay)
{
aButton.BackColor = System.Drawing.SystemColors.ControlDark;
}
aButton.Click+=new EventHandler(aButton_Click);
this.Controls.Add(aButton);
xet+=50;
}
showDate();
}

This works fine and the buttons works as planned, now to my problem. When I change month from current to upcoming or earlier I like to relocate the buttons (x and y value) and hide for example button 31 if the next month only has 30 days. But I don't know how to adress these buttons from other functions?

Best Regards
Magnus

enjoycrack26-Oct-05 12:51

enjoycrack

26-Oct-05 12:51

hi there,

mwallon wrote:
But I don't know how to adress these buttons from other functions

Just suggest: whenever u create a button, u should store it into an arraylist
So u should be able to reference to the button via arraylist

<< >>

Wjousts26-Oct-05 12:53

26-Oct-05 12:53

I assume you're missing a aButton = new Button(); from your code somewhere?
If you are dynamically creating buttons in your loop you will need to keep a reference to them to be able to access them again. Putting them in an ArrayList is usually a good solution. Another way to do it would be to iterate through your form's ControlCollection and find your buttons again which is also an option, but if you have a lot of other controls it isn't very efficient. Another alternative would be to add a group box or a panel to your form and put all your buttons in there.

mwallon26-Oct-05 13:16

mwallon

26-Oct-05 13:16

Yes Wjousts you are right that line disapeard for some reason while I pasted the code.
The arrayList sounded very good but I didn't realy got it to work.
I just triead a simple thing like hidding one button:
btnList[1].Visible=false;
but got an error message saying:

'Object does not contain a definition for visible'

I created the list like this:
ArrayList btnList = new ArrayList();

and add buttons to it like this:
btnList.Add(aButton);

Wjousts26-Oct-05 14:47

26-Oct-05 14:47

The problem is that the array list contains objects, not buttons. btnList[1] returns an object that happens to be a button and you are responsible for casting it back to a button. In other words, like this:

<br />
Button b = (Button)btnList[1];<br />
b.Visible = false;<br />