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Hi folks
I've got an array that i am using as a refference to COM that will store the IntPtr's returned from the IEnumID.
<br />
[PreserveSig]<br />
int Next(<br />
int celt,
[MarshalAs(UnmanagedType.LPArray, SizeConst = 100)]<br />
IntPtr[] rgelt,
out int pceltFetched);
While i have it marshaling as an LPArray, the problem i face is that the pointer points to the first element (as far as I can see), and while, forwarding this array to the Next produces a new result (Assumably the next folder in the enumeration), it is only ever allocated to the first possition. The values for the celt increments properly, but the pCeltFetched is always equal to 1 after the first method call.
Am I marshaling it incorectly? I've tried using SafeArray with an IntPtr type, but the compiler keeps spitting it out.
I know that they are marshaled as in only by default, but is there some special handling procedure for selecting the index that the array should begin at?
I have also tried converting the array to a unmanaged structure, so that i can simply use a pointer to handle it, instead of marshaling to and from managed code with each call. However, i get null pointer exceptions, and it's not liking it. I'm calling like this:
IntPtr[] EnumerationArray = new IntPtr[100];<br />
IntPtr ArrayHandle = IntPtr.Zero;<br />
Marshal.StructureToPtr(EnumerationArray, ArrayHandle,true);
Cheers
Cata
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Hi, I don't know the answer to your question, but this 10 minute MSDN video[^] could very well provide the information you need to solve the problem yourself. It discusses the different ways that items are marshalled in platform invoke calls, though not specifically about COM.
BTW, assuming I knew the answer to your problem, it would be difficult to answer your question without also knowing what the COM interface actually expects. You've only listed the part that isn't using the interface correctly. [edit]I might have assumed incorrectly there, if you are referring to the common enumeration interfaces that COM defines.[/edit]
John
"You said a whole sentence with no words in it, and I understood you!" -- my wife as she cries about slowly becoming a geek.
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This is how it is written in C:
HRESULT Next(
ULONG celt,
LPITEMIDLIST *rgelt,
ULONG *pceltFetched
);
where celt is the number of items in the array that is forwarded.
rgelt is a pointer to the array.
pceltFetched is a pointer to a value that holds the number of elements in the returned array.
I shall check this video out.
Cheers
Cata
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That's the way it's supposed to work. Read the documentation in the Platform SDK for IEnumXXXX. It's just like an IEnumerator in .NET, only COM's IEnumXXXX implementations can fetch multiple results depending on what you pass into celt (the first param to Next). If you know the size of the object (like an ITEMIDLIST, which you can get with Marshal.SizeOf), you can get the offset the address and get the next object in the array using other methods in the Marshal class, or using an unsafe context.
Another way would be to create an array of ITEMIDLIST (or whatever struct you need, so long as it's defined and attributed properly) and pin the object to gets its address like so:
ITEMIDLIST[] items = new ITEMIDLIST[40];
GCHandle handle = GCHandle.Alloc(items);
int len;
iEnum.Next(items.Length, handle.AddrOfPinnedObject(), out len);
handle.Free(); Then you should be able to access the elements of the array with managed code.
Microsoft MVP, Visual C#
My Articles
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Hmmmm.
Maybe i've misinterpreted what i read.
I was under the assumption that the array that i hand to the Next object, is something akin to a stack that new PIDL's are added too, and the celt is the number of items currently on the array, or the index at which the next PIDL is added.
Seems kind of dumb now i think about it.
The PIDL that i am getting back in the first part of the array (I only get one PIDL at a time), is the one i'm looking for?
Can i continuously increment next, and store the PIDL in a purely managed array?
Cheers
Cata
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The Catalyst wrote:
Can i continuously increment next, and store the PIDL in a purely managed array?
Sure. Why not? You should use a list, though, since you'd have to resize the array yourself, or use any length property that the enum might have.
The Catalyst wrote:
I was under the assumption that the array that i hand to the Next object, is something akin to a stack that new PIDL's are added too, and the celt is the number of items currently on the array, or the index at which the next PIDL is added.
Nope. The first param is how large the array is. Since an array is just a pointer, you have to tell native APIs how many elements are in that array so it can use offsets to fill the addresses. This is true of any native API that uses arrays (even character arrays like LPTSTR).
Microsoft MVP, Visual C#
My Articles
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Thanks Heath, most helpful. I was planning on using an arraylist. 
One more question.
I'm running my call through Next, like this:
IntPtr[] EnumerationArray = new IntPtr[10];<br />
int ArrayLengthIn = 10;<br />
int ArrayLengthOut = 0;<br />
<br />
ContentEnumeration.Next(ArrayLengthIn,EnumerationArray,out ArrayLengthOut);
But I only ever get a single value returned.
I'm not sure why this is, as i know that there is more than 1 folder on my C drive. I'll have a play with one of the pointers i get back from the array, but can you see any reason why it's only returning a single value?
Cata
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COM requires the address of the first element of an array. IntPtr is the managed representation of that address. The COM implementation doesn't care about arrays, only that address, so declaring the method to accept an array and passing an array in does not matter - it's only going to assign the address of the first array element in its implementation. You need to offset that address to get additional elements, which the Marshal class (or unsafe code) can help with.
Microsoft MVP, Visual C#
My Articles
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AWESOME! Thanks DUDE!
I got it enumerating properly.. well... i got a sub folder name without it crashing, exploding, or whatever. I'll worry about getting multiple PIDL's later.
One thing is confusing me though.
My StrRetToStr, while working, does odd stuff. 0 seems to be the value that works, but in COM it's supposed to be 1-3. Is this because i'm using signed ints?
Also, my StrRetToStr method refuses to work with a string base type, no matter how I marshal it. But if i change it to a pointer, process it, and change it back, it works fine. I know it's trivial, but i don't understand why it's doin it, and it's bugging me.
Again, thanks for all your help. While i know i've got a long way to go, it's another step towards me grasping COM more completely. *grin*
Cheers!
Cata
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The Catalyst wrote:
While i know i've got a long way to go, it's another step towards me grasping COM more completely.
You REALLY need to learn COM first. Thinking you'll learn COM through .NET Interop is really a naive assumption. Learn COM first - it's difficult enough. You clearly don't understand as much about marshaling as you should. Write a few COM applications first and pick up a good book on COM. You need to know both .NET and COM appart from each other before interop'ing the two. That's pretty much a universal truth.
Microsoft MVP, Visual C#
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I've been playing with the GCHandle class, and trying to get a full array, but still not having any joy with it. The array still contains only one entry when it is returned.
IntPtr[] EnumerationArray = new IntPtr[10];<br />
GCHandle handle = GCHandle.Alloc(EnumerationArray, GCHandleType.Pinned);<br />
<br />
int ArrayLengthOut;<br />
<br />
ContentEnumeration.Next(EnumerationArray.Length,handle.AddrOfPinnedObject(),out ArrayLengthOut);<br />
<br />
handle.Free();<br />
<br />
IntPtr pTest = EnumerationArray[0];
Where can i look for information on manualy offsetting arrays? I understand how it's done in structs.
Cata
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ok i have a webservice written in foxpro and it accesses a database and passes me back information from the database how do i call this webservice
i added ref. to the webservice how do i use it can somebody give me an example
(the foxpro service generated a test.wsdl file this is the file i am adding ref. to)
thanks
chad
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Once you've added a reference to your XML Web Services (presumably in C#, since this is the C# forum), you only need to create an instance of the proxy class and call it's methods:
MyWebService service = new MyWebService();
service.MyMethod();
Microsoft MVP, Visual C#
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I am doing an application to print my companies invoices. Currently it uses the .net printing framework. I am looking to change that to straight Win32API to help speed it up. Plus that will use less resources. Three questions.
1) I can't seem to create a font with CreateFontIndirect(LOGFONT). I think that I am putting in the wrong value for the height. Could someone give me an example of how to create a font with that API?
2) I can't seem to use the DrawText function. I can print using the TextOut but I wanted to use the DrawText function for the formatting options. However, whenever I try to use it, it prints out a blank page. Could someone give me an example of how to print text with that API?
3) Does anyone know of a good resource to printing with pure Win32API?
Thanks alot for any help.
Shaun
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i've have been asked to create a gui that is a mdi in a mdi. by this i mean that the main form at a mdiparent and the host mdichildern who in turn act as a mdiparents and host their own mdi children. i've this and received a clear error say a mdiparent can not be a mdichild as well. my question is does anybody know a way around this or an alternative to a "mdi in a mdi"? any reply is appreciated.
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i've tried this too...but to no avail it wasnt possible..anyone has got any idea abt this.
CODER
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also i don't care if there's some tool i have to buy to this. at this point i'll take anything.
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At the very, very worst, you could completely avoid any built-in MDI functionality and write it yourself. Besides some interesting user-interface tweaks, MDI is basically a set of forms inside another set of forms, which can be done rather easily.
John
"You said a whole sentence with no words in it, and I understood you!" -- my wife as she cries about slowly becoming a geek.
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thats fine as it seems to be my only option but, can point in the direction to find out how to that because i'm guessing it would invole some win32 calls?
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The Win32 calls would only come in if you need to have the main form, its sub-form, and then the 3rd level sub-form all showing a title bar that indicates it is active. I'm not really if there is anything else to the base MDI document behavior.
To add a form as a child of another form, make a constructor to the (sub)form class which takes the parent as a parameter. Then, in that constructor, set TopLevel to false, and Parent to the parent form. It would look like this:
public MyMdiForm(System.Windows.Forms.Form parent)
{
InitializeComponents();
this.TopLevel = false;
this.Parent = parent;
}
To handle the look that needs multiple forms to display as active, check this[^]out.
John
"You said a whole sentence with no words in it, and I understood you!" -- my wife as she cries about slowly becoming a geek.
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Hi, I'm creating a C# windows application and I've got a problem. I need to temporarily lock a file directory, do something to a xml file in that directory, then unlock the directory. Is this possible? Can anyone help me with this? I know I need to use the Directory object somehow.
Thanks
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You can't really lock a directory, but why not just lock the XML document? It's simple using the FileStream class like so:
using (FileStream stream = new FileStream(
path, FileMode.Open, FileAccess.ReadWrite, FileShare.None))
{
XmlDocument doc = new XmlDocument();
doc.Load(stream);
}
Microsoft MVP, Visual C#
My Articles
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Is their a way to programmatically take away permissions to a folder, then give it back? I think that is what I really need to do.
Thanks!
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Yes there is, but no pure .NET way. Read NT Security Class for .NET[^], which of course only works on NT. Pay attention to the note toward the top of the page, too. There's a library written by Microsoft developers for NT security that you should use instead. That library will be included in .NET 2.0 in Q1 of 2005. Getting familiar with it now will help in the future if you upgrade your code base.
Still, though - what's the point? All you're doing is updating an XML document, so that's all that needs to be locked. Taking away permission and giving them back is dangerous if you don't account for every single exception. What if your code bombs and permissions are restored? It's not an effective solution.
If you need to update the XML document with a list of files in that directory and don't want that list to be modified while updating the XML document, the solution is simple: get a collection of filenames - which is a read-only collection of the files in that directory when you got the files. This can easily be achieved with the Directory.GetFiles static method, or the DirectoryInfo.GetFiles instance method. Update your XML document with those collections. That's an effective and proper solution.
Microsoft MVP, Visual C#
My Articles
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Hi there. I'm working on a custom control where each side can have a different border thickness. I found this code while googling which allows me to modify the controls non-client area so I can draw my borders:
[StructLayout(LayoutKind.Sequential)]
private struct RECT
{
public int Left;
public int Top;
public int Right;
public int Bottom;
}
enum WM_MESSAGE
{
WM_NCCALCSIZE = 131,
WM_NCPAINT = 133,
WM_NCHITTEST = 132,
WM_NCLBUTTONDOWN = 161,
}
[StructLayout(LayoutKind.Sequential)]
struct NCCALCSIZE_PARAMS
{
public RECT rgrc0, rgrc1, rgrc2;
public IntPtr lppos;
}
[DllImport("User32.dll")]
private extern static IntPtr GetWindowDC( IntPtr hWnd );
[DllImport("User32.dll")]
private extern static int ReleaseDC( IntPtr hWnd, IntPtr hDC );
private Rectangle _rcButton = Rectangle.Empty;
protected override void WndProc(ref Message m)
{
switch (m.Msg)
{
case (int)WM_MESSAGE.WM_NCCALCSIZE :
if (m.WParam == IntPtr.Zero)
{
NCCALCSIZE_PARAMS csp;
csp = (NCCALCSIZE_PARAMS)Marshal.PtrToStructure(m.LParam, typeof(NCCALCSIZE_PARAMS));
csp.rgrc0.Left += 1;
csp.rgrc0.Top += 5;
csp.rgrc0.Right -= 1;
csp.rgrc0.Bottom -= 1;
Marshal.StructureToPtr( csp, m.LParam, false );
}
break;
case (int)WM_MESSAGE.WM_NCPAINT :
{
IntPtr hDC = GetWindowDC(m.HWnd);
Graphics g = Graphics.FromHdc(hDC);
g.FillRectangle(SystemBrushes.Highlight, 0, 0, this.Width, 5);
g.FillRectangle(SystemBrushes.Highlight, 0, 0, 1, this.Height);
g.FillRectangle(SystemBrushes.Highlight, this.Width-1, 0, 1, this.Height);
g.FillRectangle(SystemBrushes.Highlight, 0, this.Height-1, this.Width, 1);
ReleaseDC( m.HWnd, hDC );
break;
}
}
base.WndProc(ref m);
}This works fine until the control is resized - it's client area gets reset. Any ideas on how to fix this?
"I think I speak on behalf of everyone here when I say huh?" - Buffy
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