Can someone tell what's wrong with that code? - vb.net

Question

this button is to check if there is an empty cells in the last row .
if there is filled cell the button (confirmer) will be enabled .. the application crashes when i debug
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
DataGridView1.AllowUserToAddRows = "true"
DataGridView1.ClearSelection()
DataGridView1.Rows(DataGridView1.NewRowIndex).Selected = True
Dim c As Boolean
Dim D As String
Dim nbrcell As Integer = DataGridView1.CurrentRow.Cells.Count - 1
c = Confirmer.Enabled
Do
For i As Integer = 0 To nbrcell - 1
D = DataGridView1.SelectedRows(0).Cells(i).Value
If D <> "" Then
c = True
End If
Next
Loop Until c = True
End Sub

Answer 1

I have changed your code like this:
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
DataGridView1.AllowUserToAddRows = "true"
DataGridView1.ClearSelection()
DataGridView1.Rows(DataGridView1.NewRowIndex).Selected = True
Dim c As Boolean
Dim D As Object
Dim nbrcell As Integer = DataGridView1.CurrentRow.Cells.Count - 1
c = Confirmer.Enabled
Do
For i As Integer = 0 To nbrcell - 1
D = DataGridView1.SelectedRows(0).Cells(i).Value
If Not IsDBNull(D) Then
c = True
End If
Next
Loop Until c = True
End Sub
Hope it helps

Answer 2

You are trying to read the number of cells from the CurrentRow property.
But if there is no CurrentRow set when you run this code then the code crashes with a Null Reference Exception. (A.K.A. Object Reference not set to an instance of an object)
Instead you should use the row at NewRowIndex.
Dim nbrcell As Integer = DataGridView1.Rows(DataGridView1.NewRowIndex).Cells.Count
and don't subtract 1 from the count of cells. You are doing this two times. One when you get the Count and one more time when you loop over that count (So the last cell is not checked)
Now the loop: You never exit from that loop if the cells are all filled
Dim D as Object
Dim allFilled = True
For i As Integer = 0 To nbrcell - 1
D = DataGridView1.SelectedRows(0).Cells(i).Value
If D Is Nothing OrElse
Convert.IsDBNull(D) OrElse
String.IsNullOrWitheSpace(D.ToString()) Then
allFilled = False
Exit For ' no need to continue the loop
End If
Next
Confirmer.Enabled = allFilled
I have removed the external while, the the loop is executed only using the for and it is stopped as soon as a cell with Nothing, DBNull or empty string value is found. At that point a boolean variable is set to false and applied to the Enabled property of the button. If no cells are found to be invalid then the boolen variable remains set to true and the button will be enabled.
Probably it is possible to change something in the evaluation code of the cell, but this depends on how do you fill the grid (manually or through a database data)

Answer 3

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Confirmer.Visible = True
Confirmer.Enabled = False
DataGridView1.AllowUserToAddRows = "true"
DataGridView1.ClearSelection()
DataGridView1.Rows(DataGridView1.NewRowIndex).Selected = True
Dim c As Boolean = False
Dim D As Object
Dim nbrcell As Integer = DataGridView1.CurrentRow.Cells.Count
Do
For i As Integer = 0 To nbrcell - 1
D = DataGridView1.Rows(DataGridView1.NewRowIndex).Cells(i).Value
If Not IsDBNull(D) Then
Confirmer.Enabled = True
c = True
End If
Next
Loop Until c = True
End Sub
The Problem now is that the button(confirmer) is always enabled even is the cell is empty