[2008] Check Integer For Null Value Instead Of 0

Jan 19, 2009

Basically, when you set an Integer to "Nothing" it seems to equal the same value as if you were to set it to 0. So, in a function that returns an Integer how can I return something that will show that the function failed? In most cases I would use -1 or something but in this case I need to allow for negative values too.

Here's some more detailed information: I'm using the GetValue method of the Microsoft.Win32.RegistryKey class to read a numeric value from the registry. The GetValue method has an optional argument that you can pass in that specifies what should be returned if the value did not exist, normally I would use Nothing but in this case because I am storing the returned value in an Integer then it is just the same as if the GetValue method returned 0 (which is a valid value in this case).

Example:

vb.net
Dim Reg As Microsoft.Win32.RegistryKey = My.Computer.Registry.LocalMachine
Dim SubKey As Microsoft.Win32.RegistryKey = Reg.OpenSubKey("SYSTEMCurrentControlSetControlTimeZoneInformation", False)

[Code].....

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How to check whether a column is null i use the following code but I got this error "Input string was not in a correct format."

[Code]....

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I tried to do it this way but _intDLocation = "" throws an exception

[code]...

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Feb 8, 2011

I have a function that takes in a number of parameters.. it then does a db insert.i have a foreign key on one of the fields (modelID)i want to pass a NULL if no model ID is selected.[code]but now i get an error saying: Nullable object must have a value.if i pass in a 0, it does not insert because it breaks the DB constraints.

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I have a field in a datatable (dt) that can be integer or NULL.

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If you assign a value to a nullable integer via a ternary operator, it can't become null..While this question may seem like a duplicate of many, it is actually being asked for a specific reason.Take this code, for example: Dim n As Integer? = If(True, Nothing, 1) In that code, the ternary expression should be returning Nothing, but it's setting n to 0. If this were C#, I could say default(int?) and it would work perfectly. Now it looks like I am going to have to ditch the ternary and use a regular If block, but I really want to use the ternary. If Nothing were truly VB.NET's equivalent to C#'s default, how can you explain this behavior?

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I am getting System.NullReferenceException:Object reference not set to an instance of an objectwhile executing the below code..!!

Dim arr() As Integer
Dim g,j As Integer
g=10

[code]....

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Jun 24, 2010

I have some code which gets child items for a menu via the GetChildren function which takes a list of menuData: Dim builtMenu As New List(Of MenuData)(_rawData.FindAll(Function(item) item.GroupingID = 0))

For Each menuData As MenuData In builtMenu
If menuData.Children IsNot Nothing Then
menuData.Children.AddRange(GetChildren(menuData))
End If
Next

If I check if menudata.children isnot nothing, it always is nothing because the GetChildren function is yet to run (providing the child items, which do exist). If I remove this check and just have this code:

Dim builtMenu As New List(Of MenuData)(_rawData.FindAll(Function(item) item.GroupingID = 0))

For Each menuData As MenuData In builtMenu
menuData.Children.AddRange(GetChildren(menuData))
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[Code]...

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I have a dataset. I'd like to check if one item in the dataset is null or zero.

If IsDBNull(ds.Tables(0).Rows(0)("TotalCostPerUnit")) or CInt(ds.Tables(0).Rows(0)("TotalCostPerUnit") = 0 Then
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end if

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Dim Conn As ADODB.Connection
Dim Null As String
Dim NullRecordset As ADODB.Recordset

[code]....

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I have a problem with verifying db null value. Actually I don't know the syntax.
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Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If MyBase.Dispose(disposing) <> DBNull.Value Then
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[Code]....

I am getting error

1) Expression does not produce a value.

2)Expression is a value and therefore cannot be the target of an assignment.

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I retrieve data from database like below. How do I check whether the value retrieved from database is null?

[Code]...

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Mar 2, 2011

I have multiple textboxes that are saved using my settings and buttons to add them to the clipboard.

The problem is when the textbox is blank and I click on the copy button.

The saving to my.settings happens on close so when someone enters text that they plan on saving later and then clicks the copy button, whammo it crashes.

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[Code]...

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Table contains 2 columns Tags10 and TU. Its values are:

NDX___________TUI48
JJI_________ NULL
CmdSelect.CommandText = "Select * From Tags Where Tags10='" & s_temp02 & "'" 'OK
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[code]....

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This is probally more of an elegance question than functionality. I am looking for the absolutely safest way to check for an integer from a string and an object,

Using most of the built in functions for this in .net seem to generate a first chance exception, displayed in the Immediate window, and over time they just build up. what are the implications of these exceptions as they don't seem to affect the operation of the system.

Here are my two attempts, both feel clunky and I know there has to be a better way than using VB.IsDBNull and Integer.TryParse... Or am I just being anal.[code]....

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I want to display a message if the value of cell of my datagridview is Null.

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What im trying to do is check a row for null values in my datagridview before saving the data back to my access database, in particular the first columns cell of the new row being added. This is the code I have so far'

Private Sub LatheprogramsBindingNavigatorSaveItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LatheprogramsBindingNavigatorSaveItem.Click
Dim test As String = Me.LatheprogramsDataGridView.Columns(1).ToString()

[code]....

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i hav two openfilefialogs(1 and 2). So i also have a listbox. the files opened with the openfiledialogs will be added to the listbox. and when i need to open the files i need to see if they are from which openfiledialog. so

it is like this.

Path.GetDirectoryName(OpenFileDialog1.FileName) & "" & Form3.ListBox1.SelectedItem.ToString
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I am getting product id value some times null and empty from databasehere how i check if valule null and empty

productid = IIf(IsDBNull(TempDT.Rows(0).Item("productid")) =
True,
"", TempDT.Rows(0).Item("productid"))

[code].....

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DataGridViewX.CurrentRow.Cells.Item(0).Value.ToString
If the item is blank and no data is entered it will throw a null exception, so the question is that how can I check if the item is null or not? Even using this:
If DataGridViewX.CurrentRow.Cells.Item(0).Value.ToString IsNot Nothing Then ...
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[Code]...

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