Re: from VC6 dll - C# Discussion Boards

22-Mar-04 11:56

The only way to determine whether a file exists without going to all the trouble using WebDAV extensions (which may not be supported by the web server, and often isn't for unauthenticated users) would be to make a request for it. You wouldn't have to necessary stream the response to a file, though, just check the HttpWebResponse.StatusCode.

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from VC6 dll

yyf22-Mar-04 10:10

yyf

22-Mar-04 10:10

Hi, everyone

1. When I call a function imported from a VC6 dll, it returns 42949672970 when it is supposed to return -1. Anyone knows why?

2. There's another function in this VC6 dll like this loginDlg(LPCTSTR Name, long NameLength). This function will return the login name by the first parameter, 2nd parameter is tell the function how long the buffer is.
How to import and use this kind of functions properly?

Thanks in advance.

Heath Stewart22-Mar-04 11:47

22-Mar-04 11:47

Looks like the address of a return value is being returned. How are you declaring the native function to be P/Invoked?

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yyf23-Mar-04 3:10

yyf

23-Mar-04 3:10

Here is how the function declare in the VC6 dll head file

#ifndef LONG<br />
typedef long LONG;              /* 32 bit */<br />
#endif<br />
<br />
LONG _stdcall SelectChildProjects<br />
(<br />
   LONG lProjectId               /* i  Number of parent project */<br />
);

Here is how I declare the function in my .Net code

<br />
[DllImport("dcli.dll", EntryPoint="SelectChildProjects")]<br />
public static extern long SelectChildProjects(long lProjectId);

Thanks.

Heath Stewart23-Mar-04 3:13

23-Mar-04 3:13

A LONG (long) in C++ is a 32-bit integer. A long (Int64) is a 64-bit integer. You're marshaling is all wrong which might explain why you're getting extra data from overflow. You should declare it as:

[DllImport("dcli.dll")]
public static extern int SelectChildProjects(int lProjectId);

Notice I also dropped the EntryPoint property, which you only need in cases where your declared method differs in name from the entry point exported by the native DLL.

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yyf23-Mar-04 4:01

yyf

23-Mar-04 4:01

Thank you very much! It works prefectly now.

Loop through a Datagrid

Anonymous22-Mar-04 9:55

Anonymous

22-Mar-04 9:55

Hi,

Is it possible to loop through a datagrid? For eg.

for (int i=0;i

Heath Stewart22-Mar-04 11:46

22-Mar-04 11:46

Loop through the underlying data source, not the DataGrid itself.

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Anonymous22-Mar-04 11:51

Anonymous

22-Mar-04 11:51

Actually the source is a dummy query which has no underlying table or any such database connection. The query exists only because I wanted to populate the datagrid. Its the data grid I want to manipulate actually. Or if there is another way to populate the rows and cols of a datagrid into an array that would be fine. Do you know if I can do that? I could the loop through the array and retreive the records I want.

Thanks
Al

Heath Stewart22-Mar-04 11:57

22-Mar-04 11:57

Read the documentation for the DataGrid.DataSource property in the .NET Framework SDK. It just has to be an object that implements IList or IListSource, so you could use an array or a collection as well. This is true for the rest of the data-bindable controls using a CurrencyManager.

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Ruchi Gupta22-Mar-04 12:11

Ruchi Gupta

22-Mar-04 12:11

A liitel addition to what Heath Stewart said....

grid1.DataSource = dataTable;

CurrencyManager cm = (CurrencyManager)this.BindingContext[grid1.DataSource, grid1.DataMember];

DataView dv = (DataView)cm.List;

for(int i = 0; i < dv.Count ; i++)
{
//do what u want
}

Ruchi

Heath Stewart23-Mar-04 2:46

23-Mar-04 2:46

Whether you're binding to a DataSet or DataTable, it's a lot easier to just get the table you want to enumerate and create a DataView over that table using:

DataView dv = new DataView(dataTable1);
// Or
DataView dv = dataTable1.DefaultView;

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Property questions

gkrish522-Mar-04 9:01

gkrish5

22-Mar-04 9:01

What is a limitation on a property ? I think none of the below are but am i correct ?

Choice 1
Properties cannot be inherited.
Choice 2
Properties do not allow for lazy initialization.
Choice 3
Properties cannot be defined as write-only.
Choice 4
Properties cannot return unsigned value types.
Choice 5
Properties cannot be used as method parameters.

II
(I feel "abstract" is right. Can anyone confirm ?
What modifier do you use in a base class to require any derived class to implement a property?
Choice 1
sealed
Choice 2
virtual
Choice 3
protected
Choice 4
abstract
Choice 5
mustoverride

Thanks

GK

CWIZO22-Mar-04 9:20

CWIZO

22-Mar-04 9:20

Properties do not allow for lazy initialization.

I never heard of lazy initialization.

Properties cannot be inherited.: Property itself of corse it cannot be inheriated, but as a part of a class there is no probblem.

As for second abstract is correct.

// btw: May I ask from where these questions are?

Q:What does the derived class in C# tell to it's parent?
A:All your base are belong to us!

leppie22-Mar-04 9:27

leppie

22-Mar-04 9:27

CWIZO wrote:
I never heard of lazy initialization.

Then I suggest you look at ROTOR's codebase. Its full of it. EG

object foo = null;
public object Foo
{
  get {return (foo == null) ? (foo = new object()) : foo;}
}

CWIZO wrote:
Properties cannot be inherited.: Property itself of corse it cannot be inheriated, but as a part of a class there is no probblem.
Now only a VB person would think that way! Laugh | :laugh:

^{top secret}

CWIZO22-Mar-04 9:31

CWIZO

22-Mar-04 9:31

I am not a VB person (never programmed there).
I never heard one would inheriate only the property in C#.

I am confused (maybe this would be becouse of my bad english?)

Q:What does the derived class in C# tell to it's parent?
A:All your base are belong to us!

gkrish522-Mar-04 11:20

gkrish5

22-Mar-04 11:20

I found these as part of a quiz somewhere

Does this control exists???!!!

leppie22-Mar-04 9:22

leppie

22-Mar-04 9:22

1. none, i concur with u
2. again i agree with u, mustoverride is a VB6 keyword. I reckon this catches all of them wannabe VB.NET web monkeys Laugh | :laugh:

^{top secret}

Andretux22-Mar-04 8:16

Andretux

22-Mar-04 8:16

Hello friends, how are you?

My name is André, I´m brazilian, so my english is not so good, but I hope that you understand. Wink | ;)

I need a Grid Control (or a ListView) that I can put 2 lines in the same cell....

If you could, please, see the next link, so this have a System Screen Picture that have the control I need. The control is these that contains tha products list: the product name in the first line, and the price and others informations in the second line (for each product).

http://www.acsn.com.br/Imagens/Frente%20de%20Caixa/Ampliadas/vendas%20ampliado.jpg

If you could help, I will be glad...

Thanks...

André

André

Re: Does this control exists???!!!

Heath Stewart22-Mar-04 9:05