I just want to check and see if this object is null. if i do not and it is my applications closes.I have also looked into a null reference exception. I will do whatever as long as it handles "null".[code]
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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))
Next
Then I am presented with a Object reference not set to an instance of an object error on menuData.Children.AddRange(GetChildren(menuData))
I'm using FileHelper to generate object's property. Here is an example of one property:
<FieldOptional(), _
FieldTrim(TrimMode.Both)> _
<FieldNullValue(GetType(String), " ")> _
Public StoreNo As String
As you can see the StoreNo will either have a value or " ", one of the business policy is to check if the StoreNo is empty or nothing if the object's StoreNo is empty or null then the record will not create.
I though about creating an HasValue Function in the class to check the StoreNo and other properties in the object but I feel like it is a hack.
Public Function HasValue() As Boolean
Dim _HasValue As Boolean = True
If StringHelper.IsNullOrBlank(Me.StoreNo) Then
[Code]....
I don't think this approach is an ideal solution. what if the StoreNo is remove or change to something else. What's the best approach to check object's property?
Use the "new" keyword to create an object instance & Check to determine if the object is null before calling the method. I'm reading text from a text file using the following [Code]
View 9 RepliesHow 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]....
I am making use of a 3rd party dll and am encountering some strange behavior in VB, which doesn't occur in C# Perhaps someone can explain what is going on. Anyhow, I am making use of a method in this 3rd party library which accepts an array parameter ByRef. The end result is the variable should remain null after the method call, but it is returning initialized for some reason.
[Code]...
Currently working on the status bar for application. I would like the status bar to display message errors if a user makes an invalid entry. I have a module which contains the main procedure and procedures to change the text property of my status bar. A Call is made to the procedures from one of the forms that requires the user input. The application compliles but I get an unhandled exception of type 'System.Null ReferenceException' Object reference not set to an instance of an object. [Code]
View 4 RepliesAll I want to do is check if an object is null, but no matter what I do, if it compiles, it throws a NullReferenceException just trying to check! Here's what I've done:
[Code]...
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
Exit Sub
end if
Dim Conn As ADODB.Connection
Dim Null As String
Dim NullRecordset As ADODB.Recordset
[code]....
Im trying to check my database for a null value. If the database is null, then I want it to start the timer, otherwise I want it to skip over some stuff and automatically load the main form.
I am trying to check to see if a DataSet is null or not. If it is I would like to show a MessageBox. For some reason it is not recognizing null returns and skipping the message box and going right to the Else commands. [code]....
View 3 RepliesI have a problem with verifying db null value. Actually I don't know the syntax.
Here is the code.
If Not IsDBNull(Me.DeliveryReviewDataSet.Delivery(Me.CustomerIDListBox.SelectedIndex).Signature) Then
"Signature" is the image field (binary data).
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If MyBase.Dispose(disposing) <> DBNull.Value Then
Dispose() = DBNull.Value
[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.
I retrieve data from database like below. How do I check whether the value retrieved from database is null?
[Code]...
i'm working with a database application and i want to check if there is a null value in a specific column but it works only when its not null but if its null it throws an exception automatically
i tried to change the nullvalue property of this column but i'm not able it shows a message that its not a valid property
i tried to change the source code in the code editer but it changes back automatically
I am working on a program that has many integers (q1, q2, etc.), and each of them can be 0 or 1. This is dependent on which radiobuttons are selected. I need it to check and make sure that all of the integers have a value, but since "Null" is the same as "0",
View 8 RepliesI 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.
Here is the code that is failing and I need to check to make sure that there is a value before setting the text on the windows clipboard.[code]...
How can I check if a datatable has never been set ? or Null or Nothing ? I don't mean empty Datatable ... For example,
[Code]...
[if me.textbox1.text= system.dbnull then msgbox("please inter a value")] it says system.dbnull can't be used as an expression so how can i check the if the textbox has a null value
View 13 RepliesTable contains 2 columns Tags10 and TU. Its values are:
NDX___________TUI48
JJI_________ NULL
CmdSelect.CommandText = "Select * From Tags Where Tags10='" & s_temp02 & "'" 'OK
ReaderSelect= CmdSelect.ExecuteReader() 'OK
[code]....
How to check this? If NULL there is nothing to do, if not NULL, we should put the value into s_temp03.
I want to display a message if the value of cell of my datagridview is Null.
View 1 RepliesWhat 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]....
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
'if this returns a null then go to this
Path.GetDirectoryName(OpenFileDialog2.FileName) & "" & Form3.ListBox1.SelectedItem.ToString
Check multiple expressions for null?I have this bit here[code]...
View 8 Replies 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].....
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 ...
Will throw the exception!
I have a sub that updates a form on certain occasions. Sometimes I need to update a form when some of the entries in my table will still have a NULL value. I used this code to prevent the sub from trying to fill the form fields with NULL data:
[Code]...
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].....
The code below works fine as long as there are values within an XML node (For example the <CPU>Intel</CPU> node below) but it throws an Exception error when the node value is blank/null whatever as in the example node <Monitor> </Monitor>.t's ok if the node value is blank, I just want to check for it and not throw an exception error.This question uses the following XML snippet below: Note: The tag <Monitor></Monitor> has no value in it.
<PCSettings>
<SystemSettings>
<CPU>Intel</CPU>
[code].....
I usually have a check to see if a certain database column is DBNull and if it is convert it. Current with a datatype of money in SQL 2008 with the row column containing
Null, i declare the equivalent value as Decimal (in .Net) then get the error "'DBNull' to type 'Decimal' is not valid".... How could i check this column for null and convert it?
