VB调试错误

-1

当我去调试我的项目在Visual Basic中，我得到它说的错误消息：VB调试错误

An unhandled exception of type 'System.InvalidOperationException' occurred in Name Database.exe

Additional information: An error occurred creating the form. See Exception.InnerException for details. The error is: Object reference not set to an instance of an object.

这里是我的代码：

Public Class Form1 
Dim member As String = TextBoxName.Text 
Private Sub ButtonAdd_Click(sender As Object, e As EventArgs) Handles ButtonAdd.Click 
    ListBoxName.Items.Add(member & " " & TextBoxDate.Text) 
    TextBoxDate.Text = "" 
    TextBoxName.Text = "" 
End Sub 

Private Sub ButtonRemove_Click(sender As Object, e As EventArgs) Handles ButtonRemove.Click 
    ListBoxName.Items.Remove(ListBoxName.SelectedItem) 
End Sub 

Private Sub ButtonCheck_Click(sender As Object, e As EventArgs) Handles ButtonCheck.Click 
    If ListBoxName.Items.Contains(member & " " & Date.Today.ToString) Then 
     MsgBox(ListBoxName.Items.Contains(Date.Today.ToString) & "membership needs to be renewed") 
    End If 
End Sub 
End Class

来源

2014-02-19 user3267723

读取内部异常堆栈跟踪。 – SLaks

这可能是错误：'Dim member As String = TextBoxName.Text'表单尚未创建（不是任何控件），但是您引用了其中一个控件（这不是任何控件）。声明它，但不要初始化（'member = ...'），直到FormLoad – Plutonix

什么是“内部异常堆栈跟踪”？ – user3267723

Dim member As String = TextBoxName.Text

这不能工作，TextBoxName变量在执行此分配时尚未初始化。您必须使用如下构造函数：

Dim member As String 

Public Sub New() 
    InitializeComponent() 
    member = TextBoxName.Text 
End Sub

它是设置TextBoxName控件引用的InitializeComponent（）。请注意，它仍然不太可能工作，Text属性不会被用户设置。所以会员将包含一个空字符串。除非你给设计师一个价值。这表明这更可能是正确的：

Dim member As String = String.Empty

来源

2014-02-19 18:14:05

回答

相关问题