Most simply put, I want to connect to a built in web cam in my computer using visual basic, take a single picture, and save that in a file. I have spent about an hour or so looking for a reasonable way to do this, and have found a few suggestions. Unfortunately many the methods that I have tried seem unnecessarily complicated and I have yet to see one of them work on my computer. For example, I have tried using the icam class referenced in several places, where this code
Public Class Form1
Private Sub Snap()
Dim Webcam As iCam = New iCam
Webcam.initCam(PictureBox1.Handle.ToInt32)
Application.DoEvents()
If Webcam.iRunning Then
PictureBox2.Image = Webcam.copyFrame(PictureBox1, New RectangleF(0, 0, PictureBox1.Width, PictureBox1.Height))
End If
Webcam.closeCam()
Webcam = Nothing
End Sub
Private Sub PictureBox2_Click(sender As Object, e As EventArgs) Handles PictureBox2.Click
End Sub
End Class
Threw this error:
An unhandled exception of type 'System.InvalidOperationException' occurred in facerecognition.exe
Additional information: An error occurred creating the form. See Exception.InnerException for details. The error is: Failed to initialize because CategoryName is missing.
While with some work I could probably get the class functioning as it is meant to, the issue remains that there is really no simple and clean solution to this that I know of. Does anyone have a better idea of how to do this?
Related
So basically, I believe I am using the correct code yet the database will still not update. It will work for the current session, however, when I stop and restart the program, it appears that the data has not been updated in the database.
The really interesting part is that I am using the same method to update the database elsewhere, which when used and session restarted, the database has been updated.
p.s. I also have the same adapters and binding sources set up etc on both forms
I am so confused, help pls
Code that I believe is correct but is not working: (updating on another form so I have one place where all forms update hence FRMMain. etc)
Private Sub btnConfirm_Click(sender As Object, e As EventArgs) Handles btnConfirm.Click
Dim CurrentPoints As Integer
Dim UpdatedPoints As Integer
CurrentPoints = FRMMain.MyDBDataSet.Tables("TBLPupil").Rows(looopcount)(15)
UpdatedPoints = CurrentPoints + stfPoints
FRMMain.MyDBDataSet.Tables("TBLPupil").Rows(looopcount)(15) = UpdatedPoints
FRMMain.TBLPupilTableAdapter.Update(MyDBDataSet.TBLPupil)
FRMMain.TBLPupilTableAdapter.Fill(MyDBDataSet.TBLPupil)
End Sub
Code that I am using in another form that that DOES work:
Private Sub BtnYes_Click(sender As Object, e As EventArgs) Handles BtnYes.Click
Dim Points As Integer = FRMPupil.Pointss
Dim Cost As Integer = FRMPupil.RewardCost
Points = Points - Cost
FRMPupil.LePoints = Points
MyDBDataSet.Tables("TBLPupil").Rows(FRMLogin.DBLocation)(15) = Points
FRMMain.TBLPupilTableAdapter.Update(MyDBDataSet.TBLPupil)
FRMMain.TBLPupilTableAdapter.Fill(MyDBDataSet.TBLPupil)
Me.Hide()
End Sub
My code is correct but is not working.
No, if it is not working, then it is not correct!
There are different things you can do: DRY, Dont Repeat Yourself. You are repeating the code for updating points at several places in your code. This is error prone. Write it once and re-use it, e.g. by applying the the Repository Pattern. It makes it easier to detect errors and correct them. It allows you to re-use code that has already been tested in other scenarios (on another form).
Debug, debug, debug. Place breakpoints in the not working methods and see what happens. Do all the variables have the expected values? E.g., does looopcount have the same value as FRMLogin.DBLocation? There must be a difference somewhere. See: Navigating through Code with the Debugger or the more recent article Debug your Hello World application with Visual Studio 2017.
Trying to use an access database with Visual studio 15. After failure I found a number of tutorials and followed them with a new project and new database.
The database is connecting but the data inside the database won't display (although no error) and even using the built in save function in VB results in a run time error.
If anyone can point me in the right direction I'd be grateful. Code below.
Public Class Form1
Private Sub CustomersBindingNavigatorSaveItem_Click(sender As Object, e As EventArgs) Handles CustomersBindingNavigatorSaveItem.Click
Me.Validate()
Me.CustomersBindingSource.EndEdit()
Me.TableAdapterManager.UpdateAll(Me.CustomersDataSet) 'Error is here****
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'TODO: This line of code loads data into the 'CustomersDataSet.Customers' table. You can move, or remove it, as needed.
Me.CustomersTableAdapter.Fill(Me.CustomersDataSet.Customers)
End Sub
Private Sub BindingNavigatorDeleteItem_Click(sender As Object, e As EventArgs) Handles BindingNavigatorDeleteItem.Click
End Sub
Private Sub BindingNavigatorAddNewItem_Click(sender As Object, e As EventArgs) Handles BindingNavigatorAddNewItem.Click
End Sub
End Class
The error message I get is An unhandled exception of type 'System.Data.OleDb.OleDbException' occurred in System.Data.dll
Additional information: Unspecified error.
Here is a video that I made a while ago that should be able to help you, If you have any questions about it, i can definitely help you out.
https://www.youtube.com/watch?v=vvzY0LsAUNE
Also do you definitely need to use Access? I would recommend using an SQL database because when you publish your program, the end user may have to have a link to your access database in the same spot as yours, which can be a pain.
Nevertheless here is a video i also made regarding setting up an SQL database via Visual Studio.
https://www.youtube.com/watch?v=NLs44hxV514
If you have any issue, leave a comment and i will be happy to help you out :)
Keep In Mind
Don't forget that you need to also have a Number/unique word/or something a like in the Primary key column even if you haven't added any details to the database. eg Name and so on. If not your program may crash, so you could use the Try statement to fix this issue if the Primary Key column is left empty.
I used the following code:
Sub AppStartup()
AddHandler AppDomain.CurrentDomain.UnhandledException,
Sub(sender As Object, args As UnhandledExceptionEventArgs)
Dim e = CType(args.ExceptionObject, Exception)
ShowMessage("Oops...", HandleErr(e), MessageBoxImage.Error)
End Sub
End Sub
and I don't get the property handled Although it appears this link is supposed to be his
Your link points at XAML article, your question is probably about WinForms.
Are you starting this inside VS? Please note that exception will first be handled by VS, and then by this handler. When you run as a standalone executable, it should work as expected. You don't need to set any e.Handled to anything.
While your question doesn't really make sense, I'd say its safe to say you are trying to implement an unhandled exception handler.
This article should have all the information you need.
http://msdn.microsoft.com/en-gb/library/system.appdomain.unhandledexception.aspx
So I have this form that loads a page, and after the page is loaded I want to insert the source into RichTextBox1.Text
However after the page load the program crashes(?) and gives me this error
"An unhandled exception of type 'System.AccessViolationException' occurred in Awesomium.Windows.Forms.dll
Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt."
This is my code and it is worth mentioning that I am using awesomium for this!
Public Class Form1
Dim Thread As System.Threading.Thread
Dim html_source_code As String = ""
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Control.CheckForIllegalCrossThreadCalls = False
Thread = New System.Threading.Thread(AddressOf Load_Page)
Thread.Start()
End Sub
Private Sub Load_Page()
While html_source_code = ""
If WebControl1.IsDocumentReady Then
html_source_code = WebControl1.ExecuteJavascriptWithResult("document.documentElement.outerHTML").ToString()
RichTextBox1.Text = html_source_code
End If
End While
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Thread = New System.Threading.Thread(AddressOf Load_Page)
Thread.Start()
End Sub
End Class
Thanks in advance!
Here is your first clue...
Control.CheckForIllegalCrossThreadCalls = False
This is a pretty obvious red flag. You should never use this except perhaps for very specific debugging purposes, and for very good reason. Given that the remainder of your code is full of illegal cross thread calls, it's no wonder your program is crashing.
Every single line of code you have written that is executed in a worker thread is touching UI components. You cannot do this. See this post for examples : Cross-thread operation not valid
UI controls are continuously operated on by the main thread of your application. The main thread must be able to access them to handle their associated events, draw them to the screen, etc. If another thread is modifying their contents while the main thread is attempting to read or write to them then bad things happen.
Consider a text box that the main thread is attempting to draw to the screen. It obtains a reference to the location of the string that contains the textbox's text and, in the middle of reading the string, another thread modifies the string, invalidating the reference that the main thread is using. When the main thread tries to read, its existing reference now points to an invalid memory location and, voila, access violation.
In almost all circumstances you should never, ever set CheckForIllegalCrossThreadCalls to False. Leaving it set True will raise an exception, but it gives you the opportunity to see where the problematic code is and allows you to correct it. Setting it False simply hides the illegal call, which may or may not fail, and your application will be vulnerable to random, buggy failures when those illegal calls end up causing problems. Suggest you do some reading about how to write multithreaded .NET applications. A good start would be here : StackOverflow Search.
See also : How to: Make Thread-Safe Calls to Windows Forms Controls
I have searched and searched and searched enough until my Head aches! What I am trying to do is take an ATOM feed from here: National Weather Service Alerts and incorporate it into my program, however, I don't even KNOW where to begin :( What I want to do eventually is download the Atom feed and place it in a scrolling label. I don't want to parse it pulling out sections or anything. Just want to display the NWS alert for my area. I don't expect anyone to just write out the code or anything, but any help pointing me in the right direction for programming it simply and painlessly for an intermediate vb programmer would be greatly appreciated. Please Help!
Here is a code sample that should work for your case. Assuming you already downloaded your Atom feed and saved it to your disk. If not, you may need a slight modification:
Imports System.Xml
Imports System.ServiceModel.Syndication
Public Class Form1
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
Dim messageList As New Generic.List(Of String)
Using feedReader = XmlReader.Create("X:\vi.php.webintents")
Dim feedContent = SyndicationFeed.Load(feedReader)
If feedContent Is Nothing Then Return
For Each item As Object In feedContent.Items
messageList.Add(Convert.ToString(item.Title.Text))
Next
End Using
lbl_warnings.Text = String.Join(vbNewLine & vbNewLine, messageList)
End Sub
End Class
Replace "X:\vi.php.webintents" with your file location.
For System.ServiceModel.Syndication to be available, you need to add System.ServiceModel.dll to your references (.NET 4.0). For .NET 3.5 you would use System.ServiceModel.Web.dll
I used this answer as a base for SyndicationFeed usage in this example.