Object reference not set to an instance of object in VB

Question

I try to register an account but all it says is Object reference not set to an instance of object at the dsNewRow = ds.Tables("Username").NewRow() part.

Here's the code listing.

    ElseIf inc <> -1 Then

        If Not ExistAccount(txtUsername.Text, txtPassword.Text) Then

            Dim cb As New OleDb.OleDbCommandBuilder(da)

            Dim dsNewRow As DataRow

            dsNewRow = ds.Tables("Username").NewRow()

            dsNewRow.Item(1) = txtUsername.Text
            dsNewRow.Item(2) = txtPassword.Text

            ds.Tables("Username").Rows.Add(dsNewRow)

            da.Update(ds, "Username")
            txtUsername.Clear()
            txtPassword.Clear()

            MsgBox("Your account has been created.")

        End If

    End If

End Sub

ds is Nothing or ds doesn't contains a table named UserName.... show the code that initialize and fill the dataset — Steve, Jan 07 '14 at 23:45
http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it — Ňɏssa Pøngjǣrdenlarp, Jan 08 '14 at 00:00

score 0 · Answer 1 · answered Jan 07 '14 at 23:49

If you are getting the error chances are the ds.Tables("Username") doesnt exist therefore calling a new row on a null DataTable will result in an exception. Check to ensure that the DataTabe "Username" is not null before calling the NewRow() method.

Something like (this is just an idea)

Dim dsNewRow As DataRow

If ds.Tables("Username") Is Nothing Then
    Dim dt As DataTable = New DataTable
    dt.Columns.Add("Username", GetType(String))
    dt.Columns.Add("Password", GetType(String))

    ds.Tables.Add(dt)

End If

dsNewRow = ds.Tables("Username").NewRow()

Now the whole section about creating a new table is optional and up to you if that's the direction you would like to go with if the table does not exist. Again the main point is changes are the "Username" table does not exist.

Cheers.

score 0 · Answer 2 · answered Jan 10 '14 at 06:56

0

Since DataRow type is an object, you might try

     SET  dsNewRow = ds.Tables("Username").NewRow()

answered Jan 10 '14 at 06:56

donPablo

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Set isn't needed in VB.NET – Joe Jan 10 '14 at 06:58
The TAGS on this item were set to "database vb.net ms-access registration" and I had filtered on ms-access but I did not notice the vb.net – donPablo Jan 11 '14 at 20:32

score -1 · Answer 3 · answered Jan 07 '14 at 23:44

-1

You have to use the New keyword to instanciate the Datarow as:

Dim dsNewRow As New DataRow

answered Jan 07 '14 at 23:44

SomeNickName

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The answer is incorrect – Steve Jan 07 '14 at 23:44
AND he has that in the code – Ňɏssa Pøngjǣrdenlarp Jan 08 '14 at 00:02
There is no constructor for a DataRow accessible by user code. Even if that was possible, what kind of schema such a constructor would build for that row? – Steve Jan 08 '14 at 00:10

Object reference not set to an instance of object in VB

3 Answers3