Looping through Datagridview with BackgroundWorker in vb.net

Question

Hi
I am using Datagridview with BackgroundWorker in vb.net to simultaneously check the network connectivity status of list of IP addresses but I am getting an error states that Index was outside the bounds of the array after the 1st successful ping.

Any idea what could be causing it and how I can overcome it?

Answer 1

Is your DoWork accessing the DataGridView directly? You are not supposed to do that. Windows has always not supported accessing a window by any thread that did not create the window. It can work sometimes but Microsoft does not guarantee it will work. You can create a collection (such as a List) for the DataGridView (IP) data and bind the collection to the DataGridView then the DoWork can use the collection. Descriptions of binding a collection to a DataGridView is integrated in the DataGridView Control Overview. I suggest using a BindingSource component as mentioned there. Also see Data Binding - Windows Forms .NET Framework. I am sure that Karen has examples of binding a DataGridView to a collection.

Answer 2

My guess is the array has less elements than rows in the DataGridView e.g.

Dim someArray As String() = {"", "", ""}
For rowIndex As Integer = 0 To DataGridView1.RowCount - 1
    DataGridView1.Rows(rowIndex).Cells("Column1").Value = someArray(rowIndex)
    Console.WriteLine(DataGridView1.Rows(rowIndex).Cells("Column1").Value)
Next

While this would work as there are equal elements in the array as rows in the DataGridView

Dim someArray As String() = {"1", "2", "3", "4", "5", "6", "7", "8"}
For rowIndex As Integer = 0 To DataGridView1.RowCount - 1
    DataGridView1.Rows(rowIndex).Cells("Column1").Value = someArray(rowIndex)
    Console.WriteLine(DataGridView1.Rows(rowIndex).Cells("Column1").Value)
Next

And this would assert we are in range

Dim someArray As String() = {"1", "2", "3", "4", "5"}
For rowIndex As Integer = 0 To DataGridView1.RowCount - 1

    If rowIndex < someArray.Length Then
        DataGridView1.Rows(rowIndex).Cells("Column1").Value = someArray(rowIndex)
        Console.WriteLine(DataGridView1.Rows(rowIndex).Cells("Column1").Value)

    End If
Next

Demo

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        DataGridView1.Rows.Add(New Object() {"CountMe"})
        DataGridView1.Rows.Add(New Object() {"CountMe"})
        DataGridView1.Rows.Add(New Object() {"Other"})
        DataGridView1.Rows.Add(New Object() {"CountMe"})
        DataGridView1.Rows.Add(New Object() {"CountMe"})
        DataGridView1.Rows.Add(New Object() {"CountMe"})
        DataGridView1.Rows.Add(New Object() {"Other"})
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim someArray As String() = {"1", "2", "3", "4", "5"}
        For rowIndex As Integer = 0 To DataGridView1.RowCount - 1

            If rowIndex < someArray.Length Then
                DataGridView1.Rows(rowIndex).Cells("Column1").Value = someArray(rowIndex)
                Console.WriteLine(DataGridView1.Rows(rowIndex).Cells("Column1").Value)

            End If
        Next
    End Sub
End Class