Want to display message for particular rows with list item which column value is null or blank in datagridview

Question

Dear All Master,

I Want to display message for particular rows with list item column value is null or blank in datagridview.

so I want to display the message from the list item of "column1" where the null and blank. Is there a recommended solution that is best?

Thanks

so the output should be like this :
The following rows, Column2 must have a value.
from list item column1 :
A1
A3
A5
A6
A7
or
A1,A3,A5,A6,A7
Please check

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        DataGridView1.Rows.Add(New Object() {"A1", Nothing, "C1"})
        DataGridView1.Rows.Add(New Object() {"A2", "B2", "C2"})
        DataGridView1.Rows.Add(New Object() {"A3", Nothing, "C3"})
        DataGridView1.Rows.Add(New Object() {"A4", "B4", "C4"})
        DataGridView1.Rows.Add(New Object() {"A5", 0, "C5"})
        DataGridView1.Rows.Add(New Object() {"A6", 0, "C6"})
        DataGridView1.Rows.Add(New Object() {"A7", Nothing, "C7"})




    End Sub
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim Results =
            (
                From T In DataGridView1.Rows.OfType(Of DataGridViewRow) _
                .Select(Function(r, i) New With
                                       {
                                           .Item = r,
                                           .Index = i
                                       })
                Where Not T.Item.IsNewRow AndAlso IsNothing(T.Item.Cells("Column2").Value)
            ).ToList

        If Results.Count > 0 Then
            MessageBox.Show("The following rows, Column2 must have a value." &
                            Environment.NewLine &
                            String.Join(",", Results.Select(Function(x) x.Index).ToArray))
        Else
            '
            ' Column2 has values for each row
            '
        End If
    End Sub


End Class