如何检查 ListView SubItem 中的空项或空项？

Question

I have created this listview box that when contents are double clicked the values are inserted into text boxes. There are spaces in some items and a couple have null values in the subitems. When these particular list items are clicked it crashes the software. Is there a way I can check if a subitem is null or empty?

Private Sub ListView1_DoubleClick(ByVal sender As Object, ByVal e As System.EventArgs) Handles ListView1.DoubleClick
    For i As Integer = 1 To 7
        Dim tbName As String = "TextBox" & i
        Dim matches() As Control = Me.Controls.Find(tbName, True)
        If matches.Length > 0 AndAlso TypeOf matches(0) Is TextBox Then
            Dim tb As TextBox = DirectCast(matches(0), TextBox)
            If tb.Text.Trim.Length = 0 Then
                tb.Text = ListView1.SelectedItems(0).SubItems(0).Text
                Exit Sub
            End If
        End If
    Next

Answer 1

If you want to check if a subitem is null or empty, you could add something like this line of code:

If tb.Text.Trim.Length = 0 Then
      'check if subitem isn't null and its text is not ""
       If Not IsNothing(ListView1.SelectedItems(0).SubItems(0)) AndAlso ListView1.SelectedItems(0).SubItems(0).Text <> "" Then
            tb.Text = ListView1.SelectedItems(0).SubItems(0).Text
            Exit Sub
       End if
End If

Hope this is helpful

Answer 2

Try to add some validation to ListView1.SelectedItems(0).SubItems(0).Text

It seems to be null sometimes:

Use this validation:

If Not ListView1.SelectedItems is Nothing
   AndAlso Not ListView1.SelectedItems(0) is Nothing
   AndAlso Not string.IsNullOrEmpty(ListView1.SelectedItems(0).SubItems(0).Text)  Then

                tb.Text = ListView1.SelectedItems(0).SubItems(0).Text
End if

Full code:

Private Sub ListView1_DoubleClick(ByVal sender As Object, ByVal e As System.EventArgs) Handles ListView1.DoubleClick
    For i As Integer = 1 To 7
        Dim tbName As String = "TextBox" & i
        Dim matches() As Control = Me.Controls.Find(tbName, True)
        If matches.Length > 0 AndAlso TypeOf matches(0) Is TextBox Then
            Dim tb As TextBox = DirectCast(matches(0), TextBox)
            If tb.Text.Trim.Length = 0 Then
              If Not ListView1.SelectedItems is Nothing
                     AndAlso Not ListView1.SelectedItems(0) is Nothing
                     AndAlso Not string.IsNullOrEmpty(ListView1.SelectedItems(0).SubItems(0).Text)  Then
                tb.Text = ListView1.SelectedItems(0).SubItems(0).Text
              End if
                Exit Sub
            End If
        End If
    Next