vb.net - 对象引用未设置为实例，带有..Split(",") 的公共数组

Question

我想知道下面的 vb.net 代码有什么问题。

Public Class Form10

Public IDs() As String = TextBox1.Text.Split(",")

Private Sub Form10_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    For Each id In IDs
        MsgBox(id)
    Next
End Sub

结束类

当我做

Form10.show()

我收到错误“对象引用未设置为实例”

Answer 1

您已在类中声明了一个字段，该字段将使用相应表单上尚不存在的控件中的值进行初始化。在访问字段成员上的初始化程序时，控件未初始化和加载，从而导致错误。

要保留公共 ID 声明，您可以从字段声明中删除初始化，然后将分配移至 Button1_Click 事件，如下所示：

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    IDs=TextBox1.Text.Split(",")
    ' Do something interesting with IDs now...
End Sub

Answer 2

Public Class Form10
Private Sub Form10_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim IDs() As String = TextBox1.Text.Split(",")
    Form1.somefunction(IDs)
End Sub

在 Form1 中

  Public Sub somefunction(ByVal IDs() As String)
    For Each id In IDs
        MsgBox(id)
    Next
End Sub