I am using a dataset to pull data from a DB. One of the fields in a row is NULL. I know this. However, the following vb.net code throws a StrongTypingException (in the autogenerated get_SomeField() method in the dataset designer):
If Not IsDBNull(aRow.SomeField) Then
'do something
End If
According to documentation and this question it should be fine.
In my ASP.Net Web-Application, I'm getting this error: Conversion from type 'DBNull' to type 'Boolean' is not valid.
[Code]...
Is there any better performance by checking for a true value like this:
[CODE]..............
Than like this:
[CODE]..............
I use DataGridView in my project. Everything worked fine until I added some code in the RowValidating event. During the form_load event exception is thrown on the statement that set the datasource of the DataGridView.The project uses bindingsource for the datasource of the DataGridView. My validating code is shown below:
Dim currentRow As DataGridViewRow = Me.dgExpenditure.Rows(e.RowIndex)
Dim incexpCell As DataGridViewCell = currentRow.Cells(0)
If Not Me.closingBoolean Then
[code]....
why this gives an error at run-time:
Dim mightBeNothing As List(Of String) = Nothing
Dim a As List(Of String) = IIf(mightBeNothing Is Nothing, New List(Of String)(), New List(Of String)(mightBeNothing))
I am getting ArgumentNullException on the second line. If I replace the last part with:
Dim a As List(Of String) = IIf(mightBeNothing Is Nothing, New List(Of String)(), New List(Of String)())
It works - but the constructor New List(Of String)(mightBeNothing) will never be called if mightBeNothing is nothing, so what is the issue?
I debated whether or not to ask in the database section, but decided this was probably more of a VB question, than DB.I'm performing a query on my database and add its value to a DGV. At the moment, I'm just running tests to make sure the base example works so I can expand on it for more advanced tests.[code]It doesn't matter how I add the row, just adding it causes the error. And yes, the AllowUsersToAddRows property of the DGV is set to True, which wouldn't cause this problem anyway, but I decided to be extra careful.
View 1 Repliesi want to run a query and use the result for something else in my vb.net code. I have, opened the connection, passed the query and the connection object to the SqlCommand object and read it with the datareader object. The DataReader's HasRows property's value evaluates to true but i get an InvalidOperationException when i want to access the results of the query with the DataReader.[code]
View 1 RepliesI'm currently building an application in C#, using a basic design I came up with in VB.net for applications involving openGL. Using the Tao framework in VB, I have the following method:
Private Sub checkForGlutInit()
If glut_initialized = False Then
Glut.glutInit()
[code].....
I'm having an issue with updating a couple list boxes in the form load procedure. I have an array created from a MySQL database, and when I try to add that array to more than one ListBox, I get: A first chance exception of type 'System.ArgumentNullException' occurred in System.Windows.Forms.dll
[Code]...
I have a program that throws out a string of six numbers from 1 to 37, what I need to do is check the the string for for a format you could say.I need to make sure the set of six numbers doesn't contain 4 or more numbers of the same numbers from the same set of ten(s).
Like this:I can't have: 1-3-6-7-8-12 Or 12-14-16-18-20-21 Or 21-23-26-28-30-31 Or 30-32-34-36-20-22
I can have : 1-3-6-12-17-23
////////////: 12-14-16-20-21-22
////////////: 20-1-13-23-26-30
////////////: 1-37-22-33-30-9
[Code]...
I'm getting a "IndexOutOfRangeExeption was unhandled" in my project
Private Sub LookUpButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LookUpButton.Click
'Look up the information on the state.
[Code].....
I'm about ready to give up and go another route. I just thought I'd ask here.
I am trying to update a DateTime object into a datetime field of a sql (SQL Server 2000) database.I have the following function
Public Sub Update(ByVal lastlogin as DateTime)
Using slqupdate as SqlCommand = _connection.CreateCommand()
sqlupdate.CommandType = CommandType.Text
[code].....
For Each ScreenName As String In da.settings_LinkedScreenNames
View 5 RepliesI have the following method to strip hidden and user-specified columns from a gridviewrow and return a tablerow. [Code] However, when I run this code and hit the Add method for the TableRow, I get an InvalidOperationException stating the Collection was modified; enumeration operation may not execute. I've gotten this exception before, but usually it's because I'm attempting to modify a table that is databound.
View 3 RepliesI am trying to show a dialog from one of my WPF view model commands however when i call ShowDialog() it throws a System.ArgumentException?
Here is my code:
Public ReadOnly Property OpenParser As ICommand
Get
Return New RelayCommand(Sub(param As Object) OpenParserExecute(DirectCast(param, Frame)))
End Get
[code]....
Whenever I try and get the InnerText of an element using an XmlDocument, it throws a NullReferenceException. Here is the code below:
Dim SetDoc As New XmlDocument
Dim xmlString As String = "<upload><links><bananas>apple</bananas><original>thirteen</original></links></upload>"
[Code].....
The same happens when I load exactly the same XML from file.
I have created an application using VB.NET in VS2008. When I run the app in the IDE on my development machine it works fine. It also works fine when I build it and run it as an exe on any machine that also has Visual Studio installed (at least 2005 and 2008 anyway) However, when I try to run the compiled executable on any machine without Visual Studio it throws up an error "[program name] has encountered a problem and will close..."
View 5 RepliesI have a project that I am working on which requires my datagridview to have certain columns set as readonly according to the user authentication results. But, almost every time I set readonly = true I get a nullreference exception.I have added ALL the datagridview events trying to see where I can handle this problem. The only event it calls into after I say readonly = "true" is my cell validation event. And that event always passes fine. It is after I hit f11 to continue past the "End Sub" of my validate event that I return to the calling code and all of the sudden have an exception too.
I've looked around and can't figure out how to debug this one so I am asking for help here. I have seen other bugs about scrolling content in columns and turning off scrollbars to fix random datagridview bugs but I dont know about this one. I can't find the same problem anywhere else yet.
-my admin timer elapses and I call a timeout routine which sets the grids back to readonly = true. One of my grids (one bound by datatable/bindingsource) almost always throws a nullreference when I set the readonly = true.
-when authenticating my user if their credentials pass I want to set the whole grid to readonly = false, and then individually set two columns to readonly = true so they cannot be modified while the rest of the grid is editable. I throw my nullreference here after my first individual column call to readonly = true.
I'm using multiple grids on my project, but the timeout nullreference exception seems to be tied directly to only one of my grids. In particular, this problem grid has the least complicated queries and barely any cell validation. I dont understand how it could be the cause of so much frustration. However, it seems that when changing readonly property on individual columns that both my main grids for my project will exhibit the same behaviors with the nullreference exception.
It's important to note that usually I can just drag the debugger back into the failure statement and it will actually succeed.By figuring this out I was able to set a flag if I wasn't able to change the status of the grid and recall it. Usually that fixes most things, but when it comes to doing the individual columns I cannot code my project to try/catch/recurse for each individual column.
I've got source and a test DB available if needed.I am not sure what is relevant out of my project to post? But I can offer some compensation via Paypal if someone on this board actually helps me fix my problem in a way that I can understand and troubleshoot for future projects. This is the last bit of functionality for my requirements and I have about 48 hours to get it bug free and working as designed or I will have to revert to some older spaghetti code and do a lot of this over.
Is there a way to call a function everytime it throws an error? I could use try catch, but I need to do it with unexpected errors.
View 8 RepliesI have a piece of code that I believe is the culprit in a "Object reference not set to an instance of an object" error being thrown.[code]
View 4 RepliesI use the expression below to evaluate for a certain value, '91'. If however, the value at that array position is '0B' a System.FormatException is thrown. How do I alter the evaluation so this exception won't be thrown?
View 12 RepliesI was working with a class used to update database.All things were working for 3 years perfactly.Now it started throwing exception for two records only.When i edit these two records and try to save back to db it throws exception.Else it works fine.
View 3 RepliesYes its me again with yet another problem Ok so I've now gotten round to trying to display some data from my database and displaying it in a DataGridView Heres the critical part
[Code]...
I remove the datagridviewcomboboxcolumn from the datagridview and dispose it. When I go to dispose of the datatable that is the datasource to the comboboxcolumn an ArgumentOutOfRangeException is thrown from the datagridview. Apparently the datagridview is still handling events for datagridviewcomboboxcells for comoboboxcolumns that have been removed from the datagridview.
View 8 RepliesI want to send files to my SQL server database. It works on smaller files, but when I try to send a 323MG file my byte array throws a OutOfMemoryException.Here is my code where the error happens...
Dim MediaFile As New FileInfo(txtFileName.Text)
Dim br As New IO.BinaryReader(New IO.FileStream(txtFileName.Text, IO.FileMode.Open, IO.FileAccess.Read, IO.FileShare.Read, CInt(MediaFile.Length)))[code].....
The length of the file is 339476208.When I create a BinaryReader object and pass it in a Filestream object for the file that I am wanting to send to the database through FILESTREAM. I pass the length of the file to the byte array and I get a OutOfMemoryException.I have read in several places that the solution is to break it up into byte array chunks.
i am writing a program that will store some passwords in order to make it more user friendly. Ofcourse i want to encrypt it and so i started to learn how to use the 3Des encryption method.
[Code]...
In our code base there is a function which should return either an object or nothing. The exact code is this : Return NothingThe calling method looks something like thismyObj = theClass.function()if myObj <> nothing then // fails
View 1 RepliesI am trying to get the selected rows from a listview. To achieve this, I did this:
Dim numsel As Integer
numsel = Me.ListView1.Items.Count
For countme As Integer = 0 To numsel
[Code]....
It does count the selected rows, but it always throws out the error saying "ArgumentOutOfRange Exception", or something along those lines. For example, if I selected a row, it will output the results of that row. But the loop goes on. I tried everything I can but to no avail. I specifically want to select multiple rows, and I can achieve that if someone can assist me with this simple "problem" I have.
i am trying to develop a simple app to automate binding of data from access db for filling a form in a sequential order vb 2008 express. an error keeps coming up 'expression expected' on an sql query in the code i wrote. the code is shown below:
Private
Sub STARTButton_Click(ByVal
sender As System.Object,
ByVal e
[code]....
I have a major problem. Things were going great until I came across this little bug(?) which has thrown a stick in my spokes. As I will demonstrate below, it seems that when defining certain numbers Visual Studio will throw an overflow error.
Dim T As ULong = 14774537964905701134 'Overflow error in the IDE
Dim M As ULong = ULong.MaxValue '(18446744073709551615) we are below the maximum value so it should work, right?
The one solution I have found is that we can use the following declaration instead.
Dim T As ULong = ULong.Parse("14774537964905701134")
However, to make matters even more complicated the value in question is unknown and must be compiled using CodeDOM so using the Parse method isn't an option. Unless there is some way I can determine if that value in particular will give me an overflow error.