|
 Kind of... 
"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar
The Second EuroCPian Event will be in Brussels on the 4th of September
Can't manage to P/Invoke that Win32 API in .NET? Why not do interop the wiki way!
My Blog
|
|
|
|
|
I notice there is no more use of the prefix for the type of the variable anymore. I'm use to using a variable named say "strName" to say the type is a string. Wouldn't the use of just "Name" be a little confusing if you didn't know its type just by looking naming standard for all you know it could be a integer, boolean (hopefully not!)?
|
|
|
|
|
If you are using visual studio or any other ide, you can tell my just leaving your mouse over the variable and it will give you all that info...
/\ |_ E X E GG
|
|
|
|
|
no more notepad then 
|
|
|
|
|
Take also a look at this site[^] from MSDN.
It should give you a general overview before studying the previous posted link.
www.troschuetz.de
|
|
|
|
|
|
Are you gonna extend this into a full-blown managed web browser?
Q:What does the derived class in C# tell to it's parent?
A:All your base are belong to us!
|
|
|
|
|
Currently this only renders xhtml so it would be a quite limited market 
however i am trying to make it as flexible as possible , so if i can find some sparetime
, ill try to add a standard html parser to.
i will only add features to the renderer itself , i will not start making a browser around this control.
the purpose of this lib is not really to compete with the IE ocx ,
it is only a lightweight alternative to it , if you need to display some tables and some formatted text and dont want to load a 16mb ocx into memory , you can use this lib.
//Roger
|
|
|
|
|
Hi,
I'm new to programming... so don't laugh too hard...
How do you run an Event Method (OnClick Button) from a void Method?
The Event Method requires the object and System.EventArgs variables?
How would you supply them from a none Event Method?
Also, I've noticed that I can run an Event Method from another Event Method my using:
btn_ClearTill_Click(sender, e);
Is this not a good idea?
Ron
|
|
|
|
|
myNameIsRon wrote:
How do you run an Event Method (onclick Button) from a void Method?
You can call an event handler, i assume you mean this by Event Method, from everywhere you want as long as you can access it.
myNameIsRon wrote:
The Event Method requires the object and System.EventArgs variables?
How would you supply them from a none Event Method?
As sender object you generally pass this and the EventArgs object has to be constructed.
btn_ClearTill_Click(this, new System.EventArgs());
myNameIsRon wrote:
Also, I've noticed that I can run an Event Method from another Event Method my using:
btn_ClearTill_Click(sender, e);
Is this not a good idea?
You can call an event handler from within another event handler, but it would be better to subscribe them both to the occuring event. This way both event handlers get automatically called when the event occurs.
www.troschuetz.de
|
|
|
|
|
Thanks Stefan,
I appreciate you help  )
Ron
|
|
|
|
|
Does anyone know if it's possible to have VS .NET 2003 check the DLLImport functions at compile time? FOr instance
<br />
class PlatformInvokeTest<br />
{<br />
[DllImport("C_DLL.dll")]<br />
public static extern void BridgeFn(lo);<br />
<br />
public static void Main() <br />
{<br />
try<br />
{<br />
string lo = string.Empty;<br />
BridgeFn(lo);<br />
}<br />
catch (Exception ex)<br />
{<br />
MessageBox.Show(ex.ToString());<br />
}<br />
}<br />
}<br />
While in my DLL There is no BridgeFn function that takes a string. This generates an error only on execution. While not horrible on a small scale, on a larger scale things can get pretty hairy pretty quick. If there is no way to check this at compile time any workflow suggestions to make this easier?
Thanks!
|
|
|
|
|
No, the compiler does not check these things (as you've found). Just make sure that the functions are exported from the DLL you're referencing.
As far as work flow, I really don't see why anyone would just "blindly" P/Invoke a function if they didn't know it was exported. Seems like a backward way of thinking. Typically, you P/Invoke a function because it's there, not vice versa.
If you want to see what exports are available, I recommend using depends.exe (the Dependency Walker) from the Platform SDK (installed by default with VS.NET).
Microsoft MVP, Visual C#
My Articles
|
|
|
|
|
Heath Stewart wrote:
As far as work flow, I really don't see why anyone would just "blindly" P/Invoke a function if they didn't know it was exported. Seems like a backward way of thinking. Typically, you P/Invoke a function because it's there, not vice versa.
Agreed, I don't know about you, but I have never written a program perfectly with out any mistakes before  I just wanted to avoid the case five months from now where I am trying to track down a bug and it turns out I was just passing the wrong data type in (Cause it seems like it doesn't do data type checking either) so guess that was my concern.
We basiclly have DLLs that we want to tie into because C# has such and easy way to design interfaces and that stuff. We have a lot of DLL's so it will be done on a fairly large scale.
|
|
|
|
|
But again, why would you P/Invoke a method before seeing if it either exists? That's like putting the cart before the horse.
Data-type checking isn't supported because you're marshaling to an unmanaged platform. C/C++ doesn't perform any type checking, either, except for what the compiler can perform at compile-time. In an unmanaged world, arguments and return values are only pointers on the stack (most usually). There would be no way to determine this using a managed compiler.
The best way to avoid errors is to truly understand the unmanaged and managed types, like that an unmanaged int is platform-dependent, i.e. 32 bits on a 32-bit processor and 64 bits on a 64-bit processor,thus you should use an IntPtr. A LONG is always 32 bits, hence is a managed Int32 (C#'s int primitive). A char* is a managed string (no ref or out) and should use CharSet.Ansi, where an LPTSTR is also a string but should use CharSet.Auto, etc. etc.
One thing to note is that currently in the .NET FCL Microsoft uses int where it should be an IntPtr because .NET 1.x does not support the 64-bit platform (it will in 2.0). I suspect they will either change to using IntPtr internally or maintain two different builds specifying an int for 32-bit platforms and a long for 64-bit platforms. I honestly don't know, but making your code use an IntPtr now will ensure that when it is compiled for the 2.0 framework and run on a 32- or 64-bit platform that it will work correctly.
Microsoft MVP, Visual C#
My Articles
|
|
|
|
|
Heath Stewart wrote:
But again, why would you P/Invoke a method before seeing if it either exists? That's like putting the cart before the horse.
So is there a way to do this in code? I am not the programmer writing the DLL's so while I'll try to keep my eye out the chances that something with the function (Data types etc) might change without me knowing right away.
|
|
|
|
|
This is what internal processes are for. Some version control systems alert you of changes, such as the upcoming Microsoft Team System. If something changes, the compiler won't know - it's P/Invoking an unmanaged API so there is no type metadata, plain and simple.
Microsoft MVP, Visual C#
My Articles
|
|
|
|
|
I am using the calendar control available with the webforms. Is there a way to get a week count (ie) I would like to have the count from 1-52.. I will display the corresponding week no in a label next to each week. Is there a way to calculate it, or is there a function that can be used.
Tarakeshwar
CCIE Q(Routing and Switching), MCSE Security
|
|
|
|
|
You can use the System.Globalization.Calendar class. The best way is to get the Calendar for the current CultureInfo:
CultureInfo ci = Thread.CurrentCulture;
Calendar cal = ci.Calendar;
int week = cal.GetWeekOfYear(dt, CalendarWeekRule.FirstDay,
DayOfWeek.Sunday);
Microsoft MVP, Visual C#
My Articles
|
|
|
|
|
I'm having a little problem with receiving messages from a thread of mine.
let's say i have this thread method :
private void DoSomething()
{
for (i=0;i<10000;i++)
{
sleep(100);
}
}
How could i send this message back to the calling thread ? Don't misunderstand me : i know all about postmessage, I just don't want to use it. There must be something in the framework to achieve the same goal in a .net fashion.
Thanks for any ideas.
Sacha
|
|
|
|
|
The thread can call a delegate:
<br />
public delegate void Message(string parameter); <br />
public event Message SendMessage; <br />
...<br />
this.Message += new Message( thread_SendMessage );<br />
<br />
private void thread_SendMessage( string parameter ){<br />
Console.WriteLine(parameter);<br />
}<br />
<br />
...<br />
<br />
private void DoSomething(){<br />
for (i=0;i<10000;i++) {<br />
if(Message != null){ SendMessage("hello"); }<br />
sleep(100);<br />
}<br />
}<br />
|
|
|
|
|
Thanks for your answer Corinna,
But i'm afraid this doesn't quite answer my question. using this delegate, the call will be synchronous (at least i think so). Besides, it will be executed on the DoSomething thread instead of being executed on the "calling thread". So, if i have several DoSomething threads active, i would need to lock the content of your thread_SendMessage method, which is precisely what i want to avoid.
Thanks though.
Sacha
|
|
|
|
|
That where Control.Invoke comes in, if you're calling this on a Control (or anything that implements ISynchroniseInvoke). This invokes the delegate in the thread in which the Control was created. Read more about it in the .NET Framework SDK.
Microsoft MVP, Visual C#
My Articles
|
|
|
|
|
So, if i understand well, the target object for my call needs to implement the ISynchronizeInvoke interface (I'm not working with controls), then my thread method would look like this :
private void DoSomething()
{
for (i=0;i<10000;i++)
{
EventTargetObject.BeginInvoke(new MyEventDelegate(EventTargetObject.OnEvent), null)
sleep(100);
}
}
public EventTargetClass
{
private void OnEvent()
{
//do stuff on EventTargetObject without taking care of locking
}
}
does this sound right ?
Looks like we're approaching the solution! Thanks for your answer 
|
|
|
|
|
i found an example on how to implement ISynchronizeInvoke.
http://www.componentware.net/idesign/DesktopDefault.aspx?tabindex=5&tabid=8
That's the only example i could find using google.
Thanks for pointing this interface out.
Sacha
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
