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Hello,
Thanks for the nice link it was very useful.
Still confusing how to understand the code but having a guide
on what to do is a bit more easier 
Thanks,
DAN
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You may use the Comments and Discussions section below the article and add a new message to the article writer and ask what you more want to know.
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How to generate script of a database at run time in c#.
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See here[^]
The funniest thing about this particular signature is that by the time you realise it doesn't say anything it's too late to stop reading it.
My latest tip/trick
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Wrong again! - don't worry, I won't bother going back through any more of your so called answers
return 5;
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Hey there,
I'm working on an NTFS Master File Table reader as part of a project for University. I've already got a Console API working in C++ which reads the current $MFT file/table, and i've begun work on porting the code over to C# (as per my requirements), however my version of SetFilePointerEx doesn't seem to move the file buffer pointer.
My C++ code:
BOOL __stdcall SetFileBlockLocation(HANDLE address, LARGE_INTEGER position)
{
return SetFilePointerEx(address, position, NULL, FILE_BEGIN);
}
My C# code:
public bool AssignPointerPosition(Int64 position, EFileMove movement)
{
if (this.IsBufferReady == false)
return false;
if (Win32API.SetFilePointerEx(this.block, (long)position, IntPtr.Zero, movement) == false)
{
this.errorcode = Marshal.GetLastWin32Error();
this.errorpos = MFTHaltPosition.MoveFile;
return false;
}
return true;
}
Where EFileMove is set to EFileMove.FileBegin (aka. 0)
When I run another ReadFile, it continues to read out the same block of data into the buffer (the first four bytes should be FILE, but instead reads the beginning of the NTFS block).
Does anyone have an idea why it wouldn't move the pointer forward (position is a value far above 0), and is there a solution?
Thank you,
Chris
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What does your import/p-invoke look like for SetFilePointerEx? What is this.block defined as?
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My SetFilePointerEx import looks like this:
[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool SetFilePointerEx(IntPtr fHandle, long lDistance, IntPtr lpNewPointer, EFileMove dwMove);
And the block attribute is an IntPtr:
private IntPtr block;
Which stores the file pointer created by CreateFile, and is used to read the data.
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Is SetFilePointerEx returning 0? If so, what is GetLastError reporting?
I would recommend using SafeFileHandle instead of IntPtr for the file handle.
I assume you are doing a verbatum translation of your C++ code to C#, so that you know the actual sequence of calls you are performing are valid.
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Yes, my EFileMove structure is inheriting uint.
When I get chance, i'll try converting the code to use SafeFileHandle.
When I run SetFilePointerEx and sending 0 as the distance to move, and setting the file movement to EFileMove.FileEnd, the resulting long value is always 0. It doesn't seem to adjust the pointer at all.
I'm wondering if I should try passing a LARGE_INTEGER structure through it instead?
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if SetFilePointerEx is returning false, then you should look at the error code.
<br />
if (!SetFilePointerEx(...)) {<br />
throw new Win32Exception(Marshal.GetLastWin32Error());<br />
}<br />
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It's not returning false, but the long output for the 3rd argument (if I change the argument type to ref long) returns 0 (which documented by MSDN, would return the position of the pointer, thus the pointer hasn't changed).
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The third argument is actually 64 bit unsigned, so strictly speaking long is not the correct cast.
Henry Minute
Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”
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Edit
Nevermind. Seems passing Threading.NativeOverlapped to ReadFile was causing issues with the buffer. And I also changed all IntPtr to SafeFileHandle, and it's working now. Thanks!
Previous
It makes no difference if I convert all the Int64 types long, it still doesn't adjust the pointer and my SetFilePointerEx(this.block, 0, out pos, EFileMove.FileEnd); still assigns 0 to the pos variable (and the buffer is not changed).
modified on Saturday, January 1, 2011 7:41 AM
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Not that it should make any difference, so far as I can tell, but just in case it triggers something in your brain cell.
Is the type of your EFileMove set to uint?
enum EFileMove : uint
{
FileBegin = 0,
.................
.................
{
The documentation I have read says the dwMoveNethod should be a uint.
Henry Minute
Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”
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the boundary between managed and unmanaged code does not care about the exact numeric type, all it needs is the right amount of bits. Signed and unsigned are irrelevant at run-time, as it used to be in purely native code.
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On the way in, I agree.
Although I understood that if the unmanaged part filled those bits with what it considered an unsigned value and then on return to the managed code those same bits were treated as or cast to a signed value, there is a possibility of unpredictable results.
Henry Minute
Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”
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If you use P/Invoke sufficiently correctly (it does not care about the exact integer types, all that matters is the size of the variables), the C# version should behave the same as the C++ version.
And then the MSDN documentation says: "The file pointer returned by this function is not used for overlapped read and write operations. To specify the offset for overlapped operations, use the Offset and OffsetHigh members of the OVERLAPPED structure." Maybe that explains some.
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How do I get access to dynamically created controls on a form in something like this?
form f = new form();
Button pbutton = new Button()..
TextBox pText = new TextBox()...
...
f.controls.add(pButton)
f.controls.add(pText)
....
private void MyHoverHandler(object sender, EventArgs e)
{
}
Thanks
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TextBox pText = new TextBox();
pText.Name = "MyTextBox";
f.Controls.Add(pText1);
private void MyHoverHandler(object sender, EventArgs e)
{
TextBox pText = (TextBox)this.Controls["MyTextBox"];
}
If you can't refer to the form with this, use:
Form f = ((Control)sender).FindForm();
TextBox pText = (TextBox)f.Controls["MyTextBox"];
Greets
Flo
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Thanks for the answer. This method can get tedious if you have lots of dynamic controls though. What if I had 100 buttons and 100 textboxes..etc, Do you have to maintains an array manually, or does the form have all these controls available somehow where you can just do foreach(..)?
Thanks again
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A Form (actually a Control, a Form is a Control) has a Controls collection[^] which keeps track of all the controls placed on it.
So you can do a foreach over that.
Henry Minute
Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”
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The initial posting shows him adding elements to the Controls collection ...
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