Vb.net My.settings不为空

我启动了一个新的应用程序，当表单加载时，我需要检查my.settings.username密钥是否存在

我知道如何知道密钥是空的还是空的，如何验证密钥是否存在？ 例如，我需要更改或添加到此行中的内容 比如说别的什么东西？ 如果String.IsNullOrEmpty（My.Settings.username）为空，则在该行中

这是我的密码

Private Sub trial_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Dim today As System.DateTime
    Dim answer As System.DateTime

    today = System.DateTime.Now


    Dim trialregister = Label2
    Dim username = TextBox1.Text



    Label2.Text = today
    Label6.Text = My.Settings.trialend

    If String.IsNullOrEmpty(My.Settings.username) Then
        MsgBox("Email cannot be blank!", vbExclamation, "Media Mega Voip")
        TextBox1.Focus()


    End If
    If String.IsNullOrEmpty(My.Settings.trialregister) Then
        today = System.DateTime.Now

        My.Settings.trialregister = today
        My.Settings.trialend = today.AddDays(30)
        My.Settings.Save()
    End If
    If String.IsNullOrEmpty(My.Settings.trialend) Then
        My.Settings.trialregister = today
        My.Settings.trialend = today.AddDays(30)
        My.Settings.Save()
    End If



    If My.Settings.trialregister = My.Settings.trialend Then
        Serials.Show()
        Me.Hide()

    End If
End Sub

---

以下是一种检查设置名称是否存在的方法：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    If SettingPresent("username") Then
        Debug.Print("Setting `username` present.")
    Else
        Debug.Print("Setting `username` NOT present.")
    End If
End Sub

Private Function SettingPresent(ByVal SettingName As String) As Boolean
    Try
        Dim x = My.Settings.Item(SettingName)
        Return True
    Catch ex As Exception
        Return False
    End Try
End Function