CODEWITHSUNDEEP
vb.netdatagridview
Zebriukas Dryžiukas
Zebriukas Dryžiukas

Reputation: 45

[VB.NET]Object reference not set to an instance of an object

I'm trying to add value of column from selected row on my datagridview to Collection(but I get same error if I do it with List or Array)

CODE:

Dim zdgv = MyDataGridView

    For a = 0 To zdgv.SelectedRows.Count - 1

        MsgBox(zdgv.Rows(zdgv.SelectedRows(a).Index).Cells(0).Value.ToString)
        Try
            MyCollection.Add(zdgv.Rows(zdgv.SelectedRows(a).Index).Cells(0).Value.ToString)
        Catch ex As Exception
            MsgBox(ex.Message)
            MsgBox(ex.InnerException)
        End Try

    Next

ex.Message = Object reference not set to an instance of an object

ex.InnerException = empty

ex.InnerException.Message = Makes program crash, goes to code screen, highlights MsgBox(ex.InnerException) line, and gives error: Object reference not set to an instance of an object

ADDITIONAL INFO: Using QuickWatch on zdgv gives me all info. Using it on Rows after it(zdgv) says: 'Rows' is not declared. It may be inaccessible due to its protection level.

P.S. Yes I've googled, but none problem was similar. Yes I've searched here but no info. I've tryed r/visualbasic too - nothing... I've even tryed search for c# related stuff with this error - nothing. :/

Thanks in advance.

EDIT1: I've tryed make non-databound datagridview in new project, and add one value from it to collection - same error. I guess I should go google about "Setting Reference of Object to an Instance of an Object".

EDIT2: This one was fail - newbie mistake.

EDIT3: using quickwatch on 

zdgv.Rows(zdgv.SelectedRows(a).Index).Cells(0).Value.ToString

it shows right value(correct one, without throwing errors) = "1".

Upvotes: 4

Views: 26552

Answers (4)

Steev Ba
Steev Ba

Reputation: 1

Best Solution I found Basically, the error is that your code is making use of a non-existing row.

You will merely need to turn to false the datagridview AllowUserToAddRows property. Then all your normal loops will work properly.

Dim zdgv = DataGridView1
For Each row As DataGridViewRow In zdgv.Rows
    ListBox2.Items.Add(row.Cells(1).Value.ToString) 
Next

or

For i as integer = 0 to datagridView1.rows.count - 2
    'enter code here

Next

MK :)

Upvotes: 0

Chris
Chris

Reputation: 8647

At top of code - just below public class classname and above first sub I've this: Public XXXXX As Collection

You don't' create an instance of collection and then you try add some items to it.

It should be:

Public XXXXX As New Collection

Or you need to create a new instance somewhere else before access it

XXXXX = New Collection

Upvotes: 1

Matt B-L
Matt B-L

Reputation: 253

This code works like a charm on my side.

Did you forget a New on your MyCollection?

Dim zdgv = MyDataGridView
Dim MyCollection As New Collection
For a = 0 To zdgv.SelectedRows.Count - 1

    MsgBox(zdgv.Rows(zdgv.SelectedRows(a).Index).Cells(0).Value.ToString)
    Try
        MyCollection.Add(zdgv.Rows(zdgv.SelectedRows(a).Index).Cells(0).Value.ToString)
    Catch ex As Exception
        MsgBox(ex.Message)
        If ex.InnerException IsNot Nothing Then
            MsgBox(ex.InnerException)
        End If
    End Try
Next

Upvotes: 3

Matt B-L
Matt B-L

Reputation: 253

ex.InnerException is null, and you try to access is Message attribute. It's a normal behavior. You should try something like 

        Try
            MyCollection.Add(zdgv.Rows(zdgv.SelectedRows(a).Index).Cells(0).Value.ToString)
        Catch ex As Exception
            MsgBox(ex.Message)
            If ex.InnerException IsNot Nothing Then
                 MsgBox(ex.InnerException)
            End if
        End Try

InnerException is not null only if a sub method threw an exception under it.

Upvotes: 1

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