Re: Pinvoke ddlimport - C# Discussion Boards

21-May-04 4:13

I've never written for Windows CE or using the .NET CF, but I think you might want to check into P/Invoking this[^] API call.

RageInTheMachine9532
"...a pungent, gastly, stinky piece of cheese!" -- The Roaming Gnome

c+ instead of c#

jelleo21-May-04 5:26

21-May-04 5:26

Hello,

This is a C++ function. How can I access it in C#?

Jelle

Re: c+ instead of c#

Judah Gabriel Himango21-May-04 5:52

Judah Gabriel Himango

21-May-04 5:52

Use P/Invoke (platform invoke). Please see the PInvoke.net wiki[^] for more info.

#include "witty_sig.h"

Re: c+ instead of c#

jelleo21-May-04 6:44

21-May-04 6:44

Hello,
I am using c#. How can I include this in c#?
Jelle

Re: c+ instead of c#

Dave Kreskowiak21-May-04 8:54

21-May-04 8:54

One more time... P/Invoke the function call.

See this[^] MSDN document for a little primer on P/Invoke.

RageInTheMachine9532
"...a pungent, gastly, stinky piece of cheese!" -- The Roaming Gnome

Pinvoke ddlimport

jelleo21-May-04 9:21

21-May-04 9:21

Hello Dave,
I found:
[DllImport("aygshell.dll")]
static extern uint SHFullScreen(???? hwndRequester, ??? dwState);

I do not know how to call this function with what parameters.
I found on msdn: SHFullScreen(HWND hwndRequester, DWORD dwState);

DWORD should match Int32, but HWND? InPtr is a good guess?

Finally, how can I find out what the dwstates are? I found on MSDN SHFS_SHOWTASKBAR, but what is the value of this state?

Please help.
Jelle Smile | :)

Re: Pinvoke ddlimport

Dave Kreskowiak21-May-04 9:51

21-May-04 9:51

HWND and DWORD will both translate to an Int32 in this case. It really depends on the function your calling.

To get the hWnd of your form, just use Me.Handle. The dwState constants can be found in the Aygshell.h file. Just do a search on your hard drive to find it. The constants will be written in C++ so you'll have to translate them into C# code so you can use them in your project.

RageInTheMachine9532
"...a pungent, gastly, stinky piece of cheese!" -- The Roaming Gnome

Handle to form

jelleo21-May-04 10:11

Cannot Call Invoke or InvokeAsync

21-May-04 10:11

I found the constants on my harddrive. However, I cannot get the handle with me.handle. Also this.Handle does not work in .NET compact framework.

Please help.

///SHFS_SHOWTASKBAR 0x0001
///SHFS_HIDETASKBAR 0x0002
///SHFS_SHOWSIPBUTTON 0x0004
///SHFS_HIDESIPBUTTON 0x0008
///SHFS_SHOWSTARTICON 0x0010
///SHFS_HIDESTARTICON 0x0020

GostWryter21-May-04 1:25

GostWryter

21-May-04 1:25

Hi,

I am getting an InvalidOperationException with the message:

"Cannot call Invoke or InvokeAsync on a control until
the windows handle has been created."

This message occurs only at design time (so far) when we build and run the
project no errors related to this occur. Has anyone found the cause of this?

Thanks in Advance

Dave Kreskowiak21-May-04 3:08

21-May-04 3:08

What is your control doing when it is created that requires the Invoke call?
You really shouldn't be calling Invoke in Design mode...

RageInTheMachine9532
"...a pungent, gastly, stinky piece of cheese!" -- The Roaming Gnome

Heath Stewart21-May-04 4:23

Heath Stewart

21-May-04 4:23

Actually, an instance of the control exists even at design-time but you must still make sure the handle exists (IsHandleCreated) before invoking anything that requires a valid window handle.

Microsoft MVP, Visual C#
My Articles

Grimolfr21-May-04 3:57

Grimolfr

21-May-04 3:57

You're trying to call invoke on the control before the control's window is created and the handle is assigned.

I get around this with an if/else

if (myControl.IsHandleCreated)
{
    // Do whatever you're gonna do by invoking
}
else
{
    // Do the same thing, but on the current thread
    // instead of using invoke
}

Grim

(aka Toby)

MCDBA, MCSD, MCP+SB

Need a Second Life?[^]

Heath Stewart21-May-04 4:24

Heath Stewart

21-May-04 4:24

Another common way is if the handle isn't created (see IsHandleCreated) to queue the operation and invoke it when the HandleCreated event if fired. Many classes in the .NET FCL (especially in Windows Forms) do this.

Microsoft MVP, Visual C#
My Articles

Dave Kreskowiak21-May-04 4:36

21-May-04 4:36

I've never actually had to do it, so I'm curious as to how it gets queued? I'd tear into the class code with the disassembler but I'm nowhere near a machine with VS.NET on it at work.

RageInTheMachine9532
"...a pungent, gastly, stinky piece of cheese!" -- The Roaming Gnome

Heath Stewart21-May-04 4:42

Heath Stewart

21-May-04 4:42

All you need is the .NET Framework SDK (which requires the .NET Framework). VS.NET just installs the SDK if you opt for it, but it doesn't come with just the SDK as well.

If you were to set a property for example, the set accessor would contain something like this:

if (IsHandleCreated)
{
  SendMessage(Handle, SOME_MESSAGE, 0, value); // Just making stuff up
  fieldSet = true;
}
else
{
  fieldSet = false;
}
fieldName = value;

In the override to OnHandleCreated, you'd have something like this:

if (!fieldSet)
  SendMessage(Handle, SOME_MESSAGE, 0, fieldName);

To do this with delegates wouldn't be a whole lot different since you can store the delegate in a field or an IList and invoke it later.

Microsoft MVP, Visual C#
My Articles

Dave Kreskowiak21-May-04 4:44

21-May-04 4:44

I thought of that, but was quickly shot down. I can't install it on anything where I work...

RageInTheMachine9532
"...a pungent, gastly, stinky piece of cheese!" -- The Roaming Gnome

Dave Kreskowiak21-May-04 4:43

21-May-04 4:43

Nevermind. I found a couple of examples of the technique. D'Oh! | :doh:

I've been up for four hours and still can't keep my mind or eyes open... Roll eyes | :rolleyes:

RageInTheMachine9532
"...a pungent, gastly, stinky piece of cheese!" -- The Roaming Gnome

best pratice

the last free name21-May-04 1:25

the last free name

21-May-04 1:25

Hi all,
I need some advice on the best method to impelemt some functionality.

I have a reader obj that reads all the files in a folder, running in a thread. After each file has been read I call a processor obj to manipulte the data and fill a database. I'd like to process one file while reading the next, but limit the processor to only one instance (to prevent duplication of data in the DB). If the reader finishes reading before the processor it should wait until the processor is done its current data load, but if the porcessor has finished then the reader should make a new processor and then continue to read the next file.
So whats the best method of controling the reader depending on the state of the processor?

I should point out that I'm fairly new to C# (six months)

Thanks

Re: best pratice

Dave Kreskowiak21-May-04 3:18