Re: object reference not set to an instance of an object error [modified] - Visual Basic Discussion Boards

I don't see where dsData is getting Initialized. Is your database code working?

Mike Lasseter

which database code. I am not sure which one. I wanted to post my program here, but I don't know how to do that. Can you tell me where to initialize my dsdata

<br />
Dim dsData As DataSet  '--THIS VARIABLE IS NOT GETTING INITIALIZED/SET<br />
Dim stSQL As String<br />
<br />
stSQL = "Select * from testbackup Where barcodeid = '" & Value & "'"<br />
<br />
'THIS IS DB CODE I AM TALKING ABOUT<br />
'Database code to return dataset to dsData<br />
<br />

Without seeing the code I can't say exactly where your problem is, but here are some things to check.
1. Is the dsData nothing when you step through your code?
2. If not does it contain any tables?

My guess is the dsData is not getting populated correctly in the Database Code

Mike Lasseter

can i e-mail you my program, so you can see what is happening. let me know. thanks for your help so far

Just post the code for 'Database code to return dataset to dsData in the forum. It shouldn't be that long.

Mike Lasseter

I am not sure what to put in that area. Would you be able to help me with that if you don't mind. thanks

That is what is giving you your problem. Try looking at the following link.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconcreatingusingdatasets.asp[^]

Mike Lasseter

Alright I looked at the website and this is what I got out of it. This is what I have so far, but when I run the program now I don't get anything. It does not go to form2. It just stays at form1 even when I hit the search button. I must have done something wrong and I can't figure out. I am trying my best to figure out. Any help will be appreciated. Thanks again

Public Sub New(ByVal Value As String)<br />
            Dim dsData As DataSet = New DataSet("BackupInfo")<br />
            Dim stSQL As String<br />
            Dim backupTable As DataTable = dsData.Tables.Add("testbackup")<br />
<br />
            stSQL = "Select * from testbackup Where barcodeid = '" & Value & "'"<br />
<br />
            'Database code to return dataset to dsData<br />
<br />
<br />
            backupTable.Columns.Add("Barcodeid", Type.GetType("System.Int32"))<br />
            backupTable.Columns.Add("location", Type.GetType("System.Int32"))<br />
            backupTable.Columns.Add("datein", Type.GetType("System.String"))<br />
            backupTable.Columns.Add("dateout", Type.GetType("System.String"))<br />
            backupTable.Columns.Add("timein", Type.GetType("System.String"))<br />
            backupTable.Columns.Add("timeout", Type.GetType("System.String"))<br />
            backupTable.Columns.Add("comment", Type.GetType("System.String"))<br />
<br />
            Select Case dsData.Tables(0).Rows.Count<br />
                Case 1 'One Row Returned<br />
                    HasData = True<br />
                    TheData = dsData.Tables(0).Rows(0)<br />
                Case 0 'No Rows Found<br />
                    HasData = False<br />
                    TheData = Nothing<br />
                Case Else 'More then one row returned<br />
                    'Decided how to handle<br />
                    HasData = True<br />
                    TheData = dsData.Tables(0).Rows(0)<br />
            End Select<br />
<br />
<br />
        End Sub

-- modified at 16:57 Saturday 22nd July, 2006

You need to fill the dataset with the data from the database. Look at the link below.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconpopulatingdatasetfromdataadapter.asp[^]

Mike Lasseter

Alright. I finally made progress with your help. thanks a lot. But now when I run the program I get the message that I put in "not valid". It is not picking up the record. This is the code I have so far. Any help will be appreciated. Thanks

Public Sub New(ByVal Value As String)<br />
            Dim dsData As DataSet = New DataSet1<br />
            Dim stSQL As String<br />
            Dim backupTable As DataTable = dsData.Tables.Add("testbackup")<br />
<br />
            stSQL = "Select * from testbackup Where barcodeid = '" & Value & "'"<br />
<br />
            'Database code to return dataset to dsData<br />
<br />
<br />
            Dim orderConn As OleDb.OleDbConnection = New OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;" & _<br />
                                                       "Data Source=backup.mdb;")<br />
            Dim orderDA As OleDb.OleDbDataAdapter = New OleDb.OleDbDataAdapter("SELECT * FROM testbackup", orderConn)<br />
<br />
           <br />
            orderConn.Open()<br />
<br />
            Dim custDS As DataSet = New DataSet<br />
<br />
           <br />
            orderDA.Fill(custDS, "testbackup")<br />
<br />
            orderConn.Close()<br />
<br />
            backupTable.Columns.Add("Barcodeid", Type.GetType("System.Int32"))<br />
            backupTable.Columns.Add("location", Type.GetType("System.String"))<br />
            backupTable.Columns.Add("datein", Type.GetType("System.String"))<br />
            backupTable.Columns.Add("dateout", Type.GetType("System.String"))<br />
            backupTable.Columns.Add("timein", Type.GetType("System.String"))<br />
            backupTable.Columns.Add("timeout", Type.GetType("System.String"))<br />
            backupTable.Columns.Add("comment", Type.GetType("System.String"))<br />
<br />
            Select Case dsData.Tables(0).Rows.Count<br />
                Case 1 'One Row Returned<br />
                    HasData = True<br />
                    TheData = dsData.Tables(0).Rows(0)<br />
                Case 0 'No Rows Found<br />
                    HasData = False<br />
                    TheData = Nothing<br />
                Case Else 'More then one row returned<br />
                    'Decided how to handle<br />
                    HasData = True<br />
                    TheData = dsData.Tables(0).Rows(0)<br />
            End Select<br />
<br />
<br />
        End Sub

This is the code where it says not value.

Private Sub btnSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSearch.Click<br />
        Dim oForm2Data As New Form2.Form2Data(Me.txtbarcodeid.Text)<br />
<br />
        If oForm2Data.HasData Then<br />
<br />
            Form2.Initialize(Me, oForm2Data)<br />
<br />
        Else<br />
            ' The Data does not exists for the item in the textbox<br />
            MsgBox("Not valid")<br />
        End If<br />
    End Sub

i have experienced like this one too.
the problem was the data type. How come???
let see your code below :

stSQL = "Select * from testbackup Where barcodeid = '" & Value & "'"

if we see at barcodeid = '" & Value & "'" , we can say that barcodeid is string data type.
But it's possible in your datasource, the barcodeid is integer..

so the solution is remove ' charachters, and it will be like this:

stSQL = "Select * from testbackup Where barcodeid = " & Value

-- modified at 7:43 Friday 4th August, 2006

hiiii all
please i need to find the hard disk (volume) serial number,
the number that is given to the hard disk from manufacturer not the one that changes after formating the hard disk.
can anyone help me to this in VB.Net please Cry | :((

mayoush

Windows Management Instrumentation (WMI)

You can also try this code

<br />
Dim moReturn As Management.ManagementObjectCollection<br />
Dim moSearch As Management.ManagementObjectSearcher<br />
Dim mo As Management.ManagementObject<br />
moSearch = New Management.ManagementObjectSearcher("Select * from Win32_PhysicalMedia")<br />
moReturn = moSearch.Get<br />
For Each mo In moReturn<br />
   MsgBox(Trim(mo("SerialNumber")))<br />
Next<br />

regards
Mubashir

hi thx for your help,
but the VB.Net didn't recognize the "Management.ManagementObjectCollection"
do i need to import anything for it to work?
thx again for your help;)
i do Appritiate it Smile | :)

You need to import System.Management
You have to select
Project Menu --> Add Reference --> .NET tab --> System.Manegement

Regards,

Chatura Dilan

it did work
thx a lot Smile | :)

I'm taking a VB.Net course. I've written several ASP.Net apps. My employer gave me a new PC with Windows XP and now I can not get into any of the programs I wrote, all were working on the old PC.

The message is:
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level. This error can be caused by a virtual directory not being configured as an application in IIS.

It points to this line of code in the webconfig file:

<authentication mode="Windows">

On both the old and the new PC my code is on the C drive in INETPUB/WWWROOT

open your IIS . right click on the project folder and click properties. Press the Create Button on the pop window selected tab. click ok and try now it will work.

Rizwan Bashir

thanks, but I can't find anything like a Create Button.
By project folder - do you mean the folder .VBPROJ?
When I right click on properties I the tabs are GENERAL SECURITY and SUMMARY. I check all the other folders , dont see any create button

Hi At site http://www.windowsforms.net/FAQs/default.aspx?PageID=3&CategoryID=3&SubcategoryID=4 under the link "How do I create a ComboBox column in a DataGrid?"
they say that you cannot have the ComboBox bound with the same
BindingContext to the same datasource as the datagrid. I wounder why and
what they mean with not the same BindingContext, the DataSource or the DataMember or what

Thanks for answers

Fia

vb 6 .. long time back.. well I remember that there are two functions
1. DateFormat
2. Format

use either of them to set the date format. format will be "dd/MM/yyyy"

Rizwan Bashir

Hi,

I am stuck with this problem for weeks. To put it simple, for example, I have two related tables in MS SQLServer 2000 express: Author and Publications. The Publications table has a foreign key author_id and its primary key is of type int, which Identity is set to "Yes", Seed is set to "0". After playing with the tables for a while, when I use the addnew() to add a new record in the "Publication" table, the index number of the author_id always give me a wrong number: 2 more than the desired number. For example, I have the last record with author_id = 100 in my database, when I try to add the new record, it always give me the author_id of 103. So after update(), there are two records shown here, one with author_id 101 and the other 103. Of course the 103 is wrong, and if I keep working with this fake record, an error with occur. I have to close the form and reopen it, then only the desired record with author_id 101 shown up. The following is the addnew function I used:

Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click

Me.BindingContext(DsAuthorPub, "Author.AuthorPub").EndCurrentEdit()
Me.BindingContext(DsAuthorPub, "Author.AuthorPub").AddNew()

End Sub

Could anyone please give me some hint why I have this problem and how to deal with it?

Thanks alot,

VBDotNetNewbie

VBDotNetNewbie

Sorry for the confusion of the question I just posted, what doesn't show right is the "publication_id" not the "Author_id". Sigh | :sigh:

VBDotNetNewbie

Someone to help me with a vb6 code that can save Picture into an access/SQL Server database.
Presently i save the Picture Path as a string inside the database table but i want the actual picture to be saved as part of the table.

What is the implication of saving picture inside access table?

t.aransiola