COM - STRRET Issues - C# Discussion Boards

Re: Changing border color in a Win Button control.

23-Feb-04 9:16

Why don't you just set Button.FlatStyle to FlatStyle.Flat?

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jose.cebrian23-Feb-04 22:31

jose.cebrian

23-Feb-04 22:31

Thanks Heath, but the flat style include the border too.

The problem is that the border color and the text color are controlled by the same property, no matter the FlatStyle selected.

I think that i need to override a Paint method or something similar.

Cheers! Smile | :)

COM - STRRET Issues

Tristan Rhodes23-Feb-04 8:34

Tristan Rhodes

23-Feb-04 8:34

I'm trying to run the GetDisplayName method of a folder (in this case, the desktop folder). It all executes perfectly as far as I can see, until it reaches the StrRetToStr method, where it crashes with a null pointer error.

I'm slightly confused as its practicaly identical to the tutorial on this site, and all values forwarded are allocated succesfuly by previous functions.

The code follows:

			//Allocate Desktop pidl<br />
			IntPtr desktopPIDL = new IntPtr();<br />
<br />
			//Get desktop folder<br />
			COMStuff.SHGetDesktopFolder(out desktopPIDL);<br />
<br />
			//Set Shell interface type<br />
			Type shellType = typeof(IShellFolder);<br />
<br />
			//Build COM object<br />
			IShellFolder shellFolder = (IShellFolder)<br />
				Marshal.GetTypedObjectForIUnknown(desktopPIDL, shellType);<br />
<br />
<br />
			//Alcoate Interface ptr and relative PIDL ptr<br />
			IntPtr interfacePtr = new IntPtr();<br />
			IntPtr relativePIDL = new IntPtr();<br />
			<br />
			//Get GUID<br />
			Guid myGUID = Marshal.GenerateGuidForType(shellType);<br />
			<br />
			//Bind to parent<br />
			result = COMStuff.SHBindToParent(desktopPIDL,<br />
				myGUID,		//GUID!<br />
				out interfacePtr,<br />
				out relativePIDL);<br />
<br />
			//Build myShellFolder<br />
			IShellFolder myShellFolder = (IShellFolder)Marshal.GetTypedObjectForIUnknown(interfacePtr,shellType);<br />
<br />
			//NOTE: Must be tied to parent folder!<br />
			//Allocate STRRET<br />
			mySTRRET = new STRRET();<br />
			//Get relative PIDL<br />
			result = myShellFolder.GetDisplayNameOf(relativePIDL,SHGDN_Flags.SHGDN_NORMAL | SHGDN_Flags.SHGDN_FORPARSING<br />
						,ref mySTRRET);<br />
			//mySTRRET.uType = 2;<br />
<br />
<br />
			//Allocate File name string<br />
			myFileName = new string(' ',128);<br />
<br />
			//Run Conversion<br />
			result = COMStuff.StrRetToStr(mySTRRET, relativePIDL, out myFileName);

The calling code above gets to the last line before crashing.. STRRET has all it's values set to the same PIDL, which is expected, as the type is identifiened by the type value. However, the type value remains 0 regardless of the flags on the STRRET structure returned by the GetDisplayName of.

The STRRET struct and the StrRetToStr method are declared as follows:

<br />
[StructLayout(LayoutKind.Explicit, CharSet = CharSet.Auto)]<br />
public struct STRRET<br />
{<br />
[FieldOffset(0)]<br />
public uint uType; //1 = PoleStr, 2 = int Offset, 3 = string (char[Max_Path])<br />
<br />
[FieldOffset(4)]<br />
public IntPtr pOleStr; //Pointer to the OLE string<br />
<br />
[FieldOffset(4)]<br />
public UInt32 uOffset; //Offset into the IID list<br />
<br />
[FieldOffset(4)]<br />
public IntPtr cStr; //String Pointer<br />
<br />
}<br />
<br />
<br />
<br />
[DllImport("shlwapi.dll", CharSet=CharSet.Auto)]<br />
public static extern int StrRetToStr(<br />
ref STRRET pstr,<br />
IntPtr pidl,<br />
[MarshalAs(UnmanagedType.BStr)]<br />
out string pbstring);<br />

I'm certain that the error lies in either the declaration of my STRRET structure, or the implementation of StrRetToStr.

I'm going to experiment with the alternative method as well, StrRetToBuf, but I susspect a similar problem will occur.

If anyone could shed some light on this subject, it would be most grateful.

regards

Cata

Heath Stewart23-Feb-04 9:14

23-Feb-04 9:14

You're not calling StrRetToStr with a ref. A struct - like I've said to you many times - is a value type. StrRetToStr requires it's address, so either use ref when declaring AND PASSING the parameter, or use GCHandle to get the address and free it when finished.

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Tristan Rhodes23-Feb-04 9:41

Tristan Rhodes

23-Feb-04 9:41

My bad, I copied and pasted some code i had beed playing with and edited the ref out of, I am actualy calling it as a Ref. Like this:

			result = myShellFolder.GetDisplayNameOf(relativePIDL,SHGDN_Flags.SHGDN_NORMAL | SHGDN_Flags.SHGDN_FORPARSING<br />
						,ref mySTRRET);<br />
			//mySTRRET.uType = 2;<br />
<br />
<br />
			//Allocate File name string<br />
			myFileName = new string(' ',128);<br />
<br />
			//Run Conversion<br />
			result = COMStuff.StrRetToStr(ref mySTRRET, relativePIDL, out myFileName);

And it's still not working, the object is assigned a value to the union members, but it's type value remains 0. I'm not sure, if this is a problem with the strucure or the GetDisplayNameOf method.

Cata

Heath Stewart23-Feb-04 11:31

23-Feb-04 11:31

Don't use out for the last parameter. A String is already a reference type. Also, when alloc'ing your myFileName variable, use '\0' (null) instead of a space. This makes sure that everything is properly null-terminated in case StrRetToStr does something differently.

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Tristan Rhodes24-Feb-04 7:34

Tristan Rhodes

24-Feb-04 7:34

I see, thanks Heath, it's running without incident now. However, my string is still unasigned after the StrRet call. The STRRET still comes out of the getName function with a type value of 0, and i'm sure that's wrong.

I played around with setting it manualy, but for values 1 and 2, it crashes, and for 3 I get a null string. I didn't think it would work, but had to try.

I can only think it would be the GetName method that's not working properly....

What are your thoughts?

Cata

Draw text on path

Werdna23-Feb-04 7:55

Werdna

23-Feb-04 7:55

Is there an easy way to draw a text on a path? Specifically if I have a curve and I want this text to go along that curve, how can I do that?
Thanks.

Re: Draw text on path

Heath Stewart23-Feb-04 9:10

Is it possible to access a variable declared in c# in an html page

23-Feb-04 9:10

Werdna wrote:
Is there an easy way to draw a text on a path?

No. Lots of calculations and direct font manipulation (if you want to scew fonts) is required. Otherwise, you must trace along the path perpendicular to the normal and draw your fonts with the correct width (of each character, which requires quite a bit of calculations) and space between characters.

It's not as easy as it sounds (if you think this sounds easy). Photoshop CS just added text path support. It hadn't had it previously and there were only a few plugins available that provided such functionality. Just as an example.

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Re: Draw text on path

Werdna23-Feb-04 14:28

Werdna

23-Feb-04 14:28

Thanks. That's what I thought. I got it to work on drawing on ellipse by using some math. It was a pain. Had to brush up on my trig.

VIJAYPAPUPAGER23-Feb-04 7:10

VIJAYPAPUPAGER

23-Feb-04 7:10

I am designing an html redirector page now since the ip of my computer keeps on changing i developed an application to detect whenever there is a change in my computers ip address this ip address is stored in a variable in my application now i want to put this variable in html redirector page is it possible.

Re: Is it possible to access a variable declared in c# in an html page

Nick Parker23-Feb-04 7:39

Nick Parker

23-Feb-04 7:39

VIJAYPAPUPAGER wrote:
I am designing an html redirector page now since the ip of my computer keeps on changing i developed an application to detect whenever there is a change in my computers ip address this ip address is stored in a variable in my application now i want to put this variable in html redirector page is it possible.

If you are writing an application that requires a static IP then you should pay the extra money and get it, DHCP shouldn't be used when a static IP is required. That said, I suppose you could write a quick app that would poll your system for its IP address and store it in a hard file, whatever style you want, be it HTML, XML or your own flavor. It just doesn't appear to be a sound solution to your problem though.

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Re: Is it possible to access a variable declared in c# in an html page

Heath Stewart23-Feb-04 9:07

23-Feb-04 9:07

In addition to what Nick said, you don't need to tell the ASP.NET application what your IP address is. It already knows. From with your page or control, just call Page.Request.ServerVariables["SERVER_NAME"]. This gets the hostname or IP address. There's other ways to get this, too, like Page.Request.Url.Host. If you like, the best place to store this would be in the Page.Application property - kind of like a session variables only they apply to the whole application so that the application can query the variables (like Page.Application["IPAddress"]) and get the same thing everywhere.

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This is odd !

Ashwin C23-Feb-04 6:43

Ashwin C

23-Feb-04 6:43

i want to distribute my C# app to a win98 platform... i installed the framework 1.1 redist on it and ran that app and this is what i get...

" ...some exception... cannot be handled.....[some process value]...[some thread value]..."

whats the conventional way of compiling an app to distribute?

isnt it simply , setting the mode to release instead of debug and then compile?

Heath Stewart23-Feb-04 6:48

23-Feb-04 6:48

You can distribute a debug assembly. You just shouldn't. You compile like you normally would. C# compiles to Intermediate Language, which all .NET languages compile to. This is JIT'd into native code and executed on the machine, essentially like Java does. This is a fundamental concept of .NET.

Your error message helps none. Changes are you're using a class that only works on Windows NT. If you actually read the documentation as you develop (now there's a concept), the docs state which operating systems are supported. If you can't give us the full details to try to help you, then please don't post. This is as informative as something stupid like, "It doesn't work".

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Ashwin C23-Feb-04 6:59

Ashwin C

23-Feb-04 6:59

ok ok chill

my app cant be specific for NT(or for that matter any other) , coz its just a normal beginner c# app. i have used simple basic XML functions and general GUI stuff, so its nothing complex. but sorry for not informing you.

the err goes like ,

application has generated an exception that cannot be handled..
pid = 0xc70(3184) tid = 0xc78(3192),

Heath Stewart23-Feb-04 7:04

23-Feb-04 7:04

Don't tell me to chill. When you post such an uninformative question, expect a uninformative answer. And yes, even some basic things (or things a beginning might think are basic) can be NT-only, like Opacity. You should understand what types you're using and members your calling. You'd be surprised at how much isn't supported on Windows.

This application exception looks more like a win32 exception, which means the .NET Framework isn't installed right. Was your application bult in VS.NET 2002 or 2003? 2002 only compiles for .NET 1.0, and 2003 only compiles for .NET 1.1. If you used the command-line compiler, which version did you use. While the .NET Framework is typically backward- and forward-compatible, it is not always.

Did you reboot after installing the framework? Is your app running locally or from across the network? There's code access security to take into account in those cases, although in Windows NT at least the message is different.

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Ashwin C23-Feb-04 7:12

Ashwin C

23-Feb-04 7:12

.NET ent architect 2k2

i tried this out on systems running .NET 1.1 and 1.037, same err on both !

Heath Stewart23-Feb-04 8:57

23-Feb-04 8:57

VS.NET 2002 builds for .NET 1.0, so make sure that .NET 1.0 (v1.0.3705) is installed. Since you said you did that, make sure you have the same service pack installed as you do on your system (you should have 1.0 sp2 installed). .NET 1.0 has not be released with sp2 included.

Finally, since it's Windows you must reboot. Even a few features in .NET require a reboot on Windows NT. It is a system-level component.

One other thing you can do (as opposed to using MessageBox, which is not a viable form of debugging and can't show you near enough) is to install the .NET Framework SDK on the machine and use cordbg.exe to step through a debug build of your application. Heck, for that matter, you can even try compiling your source using csc.exe that comes with the Framework (not the SDK). It will still compile whether certain Types or members are NT-only, but it could help determine if there are other errors when trying to compile your code (not necessarily with your code).

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