C# to VB.net Invoke error

Question

Hey all I am trying to figure out how to get the code below to work in VB.net. I already converted it from C# to VB.net:

Dim dt As New DataTable()
Dim dr As DataRow

dt.Columns.Add("Name")
dt.Columns.Add("Number")

For Each item As KeyValuePair(Of String, String) In vCardReader.dicNumName
    dr = dt.NewRow()
    dr(0) = item.Value
    dr(1) = item.Key
    dt.Rows.Add(dr)
Next

Me.Invoke(New MethodInvoker(
 Sub()
          contactNameNumList.DataSource = dt
          contactNameNumList.AllowUserToResizeRows = False
          contactNameNumList.AllowUserToResizeColumns = False
          contactNameNumList.AllowUserToOrderColumns = False
          contactNameNumList.CellBorderStyle = DataGridViewCellBorderStyle.None
          contactNameNumList.Columns(0).Width = 30
          contactNameNumList.Columns(1).Width = contactNameNumList.Width / 2 - 25
          contactNameNumList.Columns(2).Width = contactNameNumList.Width / 2 - 25
End Sub))

However, when I run the program, the error I get for the above code is this:

Object reference not set to an instance of an object.

How can I correct this error?

enter image description here

Can you use the debugger and tell us which line is throwing this error? — cost, Apr 19 '14 at 05:27
Could you humor me and put GC.KeepAlive(dt) before your Me.Invoke? Also, might want to check that your loop is actually adding things to your datatable, but that really shouldn't matter here — cost, Apr 19 '14 at 05:34
@cost Same error even with the **GC.KeepAlive(dt)** before the Me.Invoke. — StealthRT, Apr 19 '14 at 05:37
**contactNameNumList** is null (nothing populated) until it goes through that **MethodInvoke** to populate it with the **dt** data. — StealthRT, Apr 19 '14 at 05:41
@HansPassant I **don't** know if **dt** has data or not. I only know for sure that **dr** has data its trying to put into **dt** and **dt** doesn't seem to be saving it? — StealthRT, Apr 19 '14 at 05:42
Or when you sat contactNameNumList is null, do you mean contactNameNumList.DataSource is null? — cost, Apr 19 '14 at 05:43
@cost The whole box has nothing populated into it. It only gets it's data from this part of the code. — StealthRT, Apr 19 '14 at 05:43
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/51003/discussion-between-stealthrt-and-cost) — StealthRT, Apr 19 '14 at 05:46

score 0 · Answer 1 · answered Apr 19 '14 at 05:15

0

How can I correct this error?

The short answer make sure your objects are initialized. I'll assume contactNameNumList is a DataGridView and dt is a DataTable. If you created either or both of these in code make sure you used the New keyword or initialized them with real data.

answered Apr 19 '14 at 05:15

tinstaafl

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I have **Dim dt As New DataTable()** for the dt and does have values for it. The contactNameNumList is a DataGridView that was placed on the form itself. – StealthRT Apr 19 '14 at 05:16
You seem to be on the right track. **dt** doesn't seem to be holding its value each go around (see updated OP). The **dr** does have data each go around but it doesnt seem to be placed into the **dt**. – StealthRT Apr 19 '14 at 05:25
@StealthRT This has nothing to do with the internals of your datatable or datarows. I'm going by the line you mentioned the error occurring on. `contactNameNumList` is null when you're trying to assign a property of it. Either assign `contactNameNumList` before your code, or move your code to a place in the program flow where `contactNameNumList` is not null. If this is some kind of webforms or winforms app for example, make sure your code runs after any designer code that creates the grid and assigns it to `contactNameNumList`. – Asad Saeeduddin Apr 19 '14 at 06:35

C# to VB.net Invoke error

1 Answers1