vb.net 如何检查 ListView SubItem 中的空项或空项？
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How do I check for a null or empty item in a ListView SubItem?
提问by 85l00k85
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?
我创建了这个列表视图框，当双击内容时，这些值会插入到文本框中。某些项目中有空格，并且有几个子项目中有空值。当单击这些特定的列表项时，它会使软件崩溃。有没有办法可以检查子项是空还是空？
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
回答by davidsbro
If you want to check if a subitem is null or empty, you could add something like this line of code:
如果要检查子项是否为 null 或为空，可以添加类似以下代码行的内容：
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
希望这有帮助
回答by Carlos Landeras
Try to add some validation toListView1.SelectedItems(0).SubItems(0).Text
尝试添加一些验证ListView1.SelectedItems(0).SubItems(0).Text
It seems to be null sometimes:
有时似乎为空：
Use this validation:
使用此验证：
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:
完整代码：
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
