UI Marshal Class With INotifyProperty Changed?
Jan 24, 2010
creating a business layer in a .dll which at the moment is being used on a windows forms application. I have some objects with properties that use iNotifyPropertyChanged to update the UI which has all been working fine. My problem is tarted to explore using multiple threads and ing a cross-thread error because the properties are being changed on a different thread to the UI and iNotifyPropertyChanged is attempting to update the values (shown in labels) on the UI thread... shows the best way to solve my problem. The .dll will never know what Forms application is using it so I really dt want to hard code references into the objects. From what I gather this code allows you to register a form with the .dll and then add the invoke to OnPropertyChanged to avoid any threading issues. Is this correct?
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Nov 14, 2010
I am using a class to track if a user cleared their personal information found within some text boxes on a form. In the button click event to clear the text boxes I am creating a new object to the class and assigning true to one property value. Sounds simple until I try and submit the form with a different button, and create a another object reference that I use in an IF statement to check the property value for true. Every time the statement fails because the value being returned from the getter in my class is false.
[Code]...
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May 10, 2011
I've written a custom class MyClass and marked it with the <Serializable()> attribute. I have a set of binary files on my hard drive that I've serialized using BinaryFormatter that came from instances of MyClass.
I've recently changed the structure of MyClass slightly (added some properties, deleted some properties, changed a few methods, etc).
What happens when I try to deserialize the existing objects to this changed class using the code below? I've tried it and not had an error thrown or anything - but surely it can't deserialize properly when the class has changed? Is there a way I can get some useful information out of the serialized files even though I've updated the class?
Here's the code I'm using to do the serialization:
Public Sub serializeObject(ByVal obj As Object, ByVal outFilename As String)
Dim fStream As FileStream
Try
[Code]....
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May 5, 2012
I changed my Username on my computer from i.e. "xxxxxx x xxxxx" to "Dennis"
VB 2008 during a compile gave me the following error: Error reading icon 'C:Usersxxxxxx x xxxxxAppDataRoamingMicrosoftVBExpress9.0VSProjectApplication.ico' -- The system cannot find the path specified.
The file "VSProjectApplication.ico" is in 'C:UsersDennisAppDataRoamingMicrosoftVBExpress9.0'
Somewhere in the VB2008 "configuration" files I believe that I need to manually change the old path to the new path.
I found the old path in the ".suo" file. The ".suo" file is not a text file. How can I edit the .suo file, save it so that it will work?
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Jan 20, 2010
on my Form I have a DataViewGrid and some textboxes with a save button (they are filled with additional data of the selected row).Save is disabled first, when I change something in the textboxes the save button is enabled.When the user changes a gow in the grid, I want to ask before changing the grid row, if he wants to save (if the button is enabled).I am using RowEnter but this is too late, then the selected row already changed (and my textboxes already got new data)...What event can I use to ask if I should save stuff before the user changes a row?Something like BeforeRowChanging with a chance to cancel changing the row?
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Jan 14, 2009
I'm a VB6 programmer who was forced to upgrade to Visual Studio 2005 Version 8.0.50727.42 .NET Framework Version 2.0.50727. I am trying to write a call-back which will intercept a Windows message for when our USB HID device is plugged or unplugged. We have a custom .dll which handles the majority of the HID interface. I just need to call a few API's to connect to the device. I can connect and communicate.
I am looking at USB Complete Third Edition. The code examples do not compile. I'm unsure if this is because of the .NET version 2 or the 2005 dialog of VB. I cannot resolve "StructLayout..." statements, but the program appears to be working without them. I cannot get any "Marshal." statements to compile, which is where I am finding it difficult to get around.
[Code]...
Although OnDeviceChange() is being called six times, both IF statements fail. m.msg is 0x219, which is Device Change. m.WParm is always 7, m.lParm is always 0. And, this is where I'm stuck. m.lParm should be a pointer which gets me to the device path? Don't know what 7 is.
So, maybe I'm not registered to receive the proper messages from the device (or I'm looking in the wrong place). The missing step might be to call the RegisterDeviceNotification() API. This book is telling me to use frmMy.Handle declared globally as Friend frmMy As frmUSB - that gives me a null reference runtime error, so I swapped in Me.Handle for the first parameter to RegisterDeviceNotification(). It likes that. But, then it has heartburn with the buffer pointer - not so easy to resolve in Visual Basic. The call wants a LONG. I have DevBroadcastDeviceInterfaceBuffer, which the book says to use Marshal.AllocHGlobal(Size) and Size is Marshal.Sizeof(DevBroadcastDeviceInterface). Neither Marshal statement compiles and I'm not sure if it was removed in this version of .NET? Anyone? I really don't need a dynamically allocated buffer. This is quickie VB app for a single USB device.
Can anyone tell me how far down the rabbit hole I am and what I'm missing. I can tell when something changes to some USB device. I have a handle to that device supplied to me by a custom API library - probably is the HID handle.
How can I setup to receive a message when my HID USB device is unplugged or plugged in?
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Feb 20, 2012
I need an array with fix String lenghts and fix rows... I do this...
Imports System.Runtime.InteropServices
Public Class Class1
Public WPFFunktion As String
[code]....
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May 22, 2010
What is the most timers you have used in an application? I think the most I have ever used is 2.In another forum this question was asked. "I have a Timer ... I have a situation where I want to run the code in the Tick event ONLY ONCE not on the interval i have the timer set too."
I responded with Timer1_Tick(New Object, New System.EventArgs) Which led to this "The 'sender' object is VERY important when you have more than one Timer being handled by the Tick event procedure. This is because in a multi-timer tick event procedure, the only way your program knows which timer just fired is by querying the 'sender' object.When you use code like this you are putting nothing into the 'sender' object, so that if you were ever going to query it a 'kaboom' is going to happen.""...this 9 timer Tick event handler job done. Remember, all that is required is the correct timer name gets put into the ListBox." "The need for multi-timers to be handled by a single Tick event handler happens all the time. How would a real life programmer handle this? "Oh, to test the "kaboom" theory I wrote this and ran it overnight successfully:
[code]...
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Dec 15, 2009
I am using a COM library in my VB.NET app that has an asynchronous execution method and signals my application via an event when it completes. The event handler is on a different thread from the calling thread. I want to invoke another execution on the main thread when I receive the completion event. If I call directly in the event handler for another execution it starts on the new thread. How do I marshal back to the main thread. This is done in a dll not in a form.
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Jun 8, 2010
I'm trying to call the GetInterfaceInfo Windows API - it accepts a structure as one of its parameters and this structure has a member that is an array. The API populates the contents of the array when it is called and there can be any number of items in the array. How can I define such an array in my structure?
If I just use a normal .NET array like so then the program just crashes (no exception thrown)
<StructLayoutAttribute(LayoutKind.Sequential)> _
Public Structure IP_INTERFACE_INFO
Public NumAdapters As Integer
[Code]...
and this works fine, but the problem is I have to define the SizeConst attribute as you can see to something large (64 in this example) so that the API doesnt fail because the array wasnt big enough. Firstly this is a waste of memory as in most cases the number of items the API sticks in the array will be less than 10, but secondly if there was ever a case where the API wanted to put more than 64 items in then it would fail.
Using ReDim to set the length of the array at runtime seems to have no effect, and that SizeConst attribute has to be set to a constant value so there's no way I can dynamically set it.
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Dec 24, 2010
I get an AccessViolationException using this code (attempted to access protected memory, this is often an indication that other memory is corrupt) on the line in DoWaitNotify that copies the pixel data back to the location in memory. In my experience, that usually means that the array is too large, but it all seems to check out. Does image data expire after a certain time or something?
Public Class Form1
Private Const NUM_THREADS As Integer = 3
Private Original As Bitmap
[Code]....
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Jan 11, 2010
VS 2010 [RESOLVED] Marshal.ReadInt32 -> AccessViolationException
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Apr 28, 2012
I tried to translate this code to vb.net using Marshal.copy but I can't get it to work
for (int y = 0; y < bitmapdata.Height; y++)
{
byte* destPixels = (byte*)bitmapdata.Scan0 + (y * bitmapdata.Stride);
[Code]...
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Jun 20, 2012
I'm just needing a simple bit of code for vb.net that will allow me to marshal an object into a string, allowing for the saving and loading of this string so I can save my classes, needs to be simple and easy!
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Sep 24, 2010
Marshal attributes to be passed as an argument in this Declare statement? [code]...
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May 17, 2010
I've created a simple Windows Forms Application and the idea is I want to identify all instances of Excel, save any open workbooks to my desktop and close all the Excel instances down.[code]I'm pretty new to this C# business so hints on the following two possible issues I've identified would be much appreciated:The ForEach loop doesn't seem to be successfully looping through the XlApp.Workbooks collection as I was hoping.
It seems that I can't quit each Excel application which, with my current code structure, is causing an infinite loop. My suspicion is that Marshal.GetActiveObject() is locking it up and preventing it from closing?If nothing obvious jumps out then I might try the alternative method by Andrew Whitechapel mentioned and linked to on this thread.
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Dec 5, 2010
I get this error on this line: System.Runtime.InteropServices.Marshal.Copy _
(Scan0, Data2, 0, Data2.Length)
"Attempted to read or write protected memory. This is often an indication that other memory is corrupt."
I also sometimes get an error on this line:
Dim dc1 As IntPtr = CreateDC("DISPLAY", Nothing, Nothing, CType(Nothing, IntPtr))
What I'm trying to do is take a screenshot and then read the colors of pixels. I currently have a working vb.net copyfromscreen method but it's SLOW and using 100% cpu usage.
[Code]...
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Jun 14, 2011
I didn't think it fair to post a comment on Fredrik Mörk's answer in this 2 year old post, so I thought I'd just ask it as a new question instead..NB: This is not a critiscm of the answer in any way, I'm simply trying to understand this all before delving into memory management / the marshal class.
In that answer, the function GetByteArray allocates memory to each object within the given array, within a loop.Would the GetByteArray function on the aforementioned post have benefited at all from allocating memory for the total size of the provided array:
Dim arrayBufferPtr = Marshal.AllocHGlobal(Marshal.SizeOf(<arrayElement>) * <array>.Count)
I just wonder if allocating the memory, as shown in the answer, causes any kind of fragmentation? Assuming there may be fragmentation, would there be much of an impact to be concerned with? Would allocating the memory in the way I've shown force you to call IntPtr.ToInt## to obtain pointer offsets from the overall allocation pointer, and therefore force you to check the underlying architecture to ensure the correct method is used*1 or is there a better way? (ToInt32/ToInt64 depending on x86/64?)
*1 I read elsewhere that calling the wrong IntPtr.ToInt## will cause overflow exceptions. What I mean by that statement is would I use:
Dim anOffsetPtr As New IntPtr(arrayBufferPtr.ToInt## + (loopIndex * <arrayElementSize>))
I've read through a few articles on the VB.Net Marshal class and memory allocation; listed below, but if you know fo any other good articles I'm all ears![URL]..
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Dec 16, 2009
If Class X is within the scope of Class Y, is X a subclass of Y?If Class A is a sub Class of B, then is Class B considered a super class of A?if Class C inherits Class D is Class D a superclass or parent of Class C?if Class E extends Class F then we can consider Class E a child of F?if Class G inherits Class H and is within the scope of Class I then who is the parent of Class G? Classes that inherits Class J and classes that are within Class J are all sub classes of Class J?
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Apr 15, 2010
I have put this code in the global form Inherits System.Windows.Forms.Form. And then in the form that will inherit this from the global Inherits MenuStrip. "MenuStrip" is what the global form is called. But keep getting this error: Error1Base class 'MenuStrip' specified for class 'Lesson2' cannot be different from the base class 'System.Windows.Forms.Form' of one of its other partial types.
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Jul 22, 2011
I have a class (see below)
Imports Microsoft.VisualBasic
Imports System.Data.SqlClient
Public Class ClientProfile
#Region "Variables"
[CODE]...
It is in the file ClientProfile I have placed in both App_Code and also App_Code/Models
In my code behind I have the following
[CODE]...
The last word, "ClientProfile" has the scary squiggly red line below it. It is not recognizing my class.Even the Intellisense is not picking up te class. Do I have to register the class file in any way?
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Mar 14, 2012
I've got a structure that's giving me fits. I have been searching the net looking for help on this and one posting says that you shouldn't use Marshal.SizeOf but to use SizeOf instead. However, I can't seem to figure out how to do this in VB.Net.
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Sep 11, 2009
Dim a as Type=GetType(className) would gimme the type. But I have only the name of the class as string. I want something like GetType("class1") which would return the type.
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May 15, 2009
I can't make difference between public class and private class and friend and protected friend class.
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Jan 21, 2010
I can do this without problem.
Class A
End Class
Class B : Inherit A
End Class
Dim Obj1 As A = New B
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Feb 22, 2010
To make this more simple,(as I have gone further through this project I have learned a bit more)...
[Code]...
How would I execute the above statement? When multiple dropdownlist's are handled in the same sub, how do you tell which one is actually calling the sub? The post by atconway was helpful in guiding me in a direction, but I dont understand the whole concept enough to dive into the msdn library... I would probably spend all my next 7 hours today reviewing it and still not get much further :-P
[Code]...
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Oct 4, 2011
Can anyone explain exactly why Method 1 in the following code does not alter the DataTable where the other 2 methods do? It's obviously some kind of referencing issue, but why exactly?
[Code]...
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Jul 26, 2011
I'm trying to write a little utility which will check periodically and tell me if/when a web page's (could be any URL) content has changed. I've read the other postings but they don't really answer my question (as far as I can tell).I know for static pages there is a last-modified header. However, what about dynamic pages? I got Oli's comment that storing a hash of the contents works but that's not really idea because the page might simply have a time stamp on it (the date-time that the page was produced). Clearly, in this case, the content would be different on every single request even though nothing significant has changed.So, now I'm thinking to tie it to a percentage of 'changedness.' Something like, more than 5% changed will cause the 'changed' logic to run.
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Aug 6, 2009
Is there a way I can add an event for when a value is changed, because, I need to add an OnDisconnected() event that detects when the mobjlistener.Connected value has changed...would I have to do a timer, is there a way I can do an event for getting disonnected?
mobjClient = New TcpClient("IP", 5000)
I would rather not add a timer, I would rather have an event that fires when mobjlistener.Connected changes, but if I can't I will go ahead and use the timer instead.The problem I have that I need to detect when this changes is because sometimes I get disconnected for an unknown reason using the TCP Multi-User Chat, it has handlers for disconnected, but whatever is causing the disconnect, it is just not detecting it, so if I could make it so that it will trigger when this is changed, then I can stop the problem I have once and for all.
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Apr 15, 2010
Is there a simple way of tracking the change of an Mdi's children i.e. when they are created and closed, something like an event OnMdiChildListChanged (I realise this doesn't actually exist).
I am also aware that I could have a method within my Mdi that handles the creation of child forms and logs the state of them or even create an Interface that defines that a child form has a "NotifyParent" method that is then called on close of the form, but i was wondering if there was any built in events that i could plumb into?
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