“未将对象引用设置为对象的实例?" [英] "Object reference not set to an instance of an object?"

问题描述

如果文本框的文本正确，则尝试显示其他形式.当我调试时，我收到一条错误消息，提示对象引用未设置为对象的实例".代码如下:

Trying to show other form if textbox's text is correct. When I debug I get an error saying "Object reference not set to an instance of an object". The code is below:

'OK is OK button, MainForm is the form I'm trying to open     

Private Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK.Click
    Dim pass As String = My.Computer.FileSystem.ReadAllText("password.txt")
    If PasswordTextBox.Text = pass Then
        MainForm.Owner = Me
        Me.Hide()
        '"Object reference not set to an instance of an object" error when debugging on line below
        MainForm.Show()
    End If
End Sub

推荐答案

您需要创建要显示的表单的新实例.为此，您可以创建一个 T 形式的变量，然后将其显示出来.

You need to create a new instance of the form you want to display. You do this by creating a variable of form T and then showing it.

如果您不创建表单的实例，MainForm.Show() 代码将在空引用上调用 Show().

If you don't create an instance of your form the MainForm.Show() code will be invoking Show() on an null reference.

If PasswordTextBox.Text = pass Then
    Me.Hide()
    Dim theFormIWantToShow As New MainForm
    theFormIWantToShow.Show()
End If

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