My.settings不为空

Question

我启动了一个新的应用程序并加载了表单，我需要检查my.settings.username键是否存在

我知道如何知道键是否为空或null，如何验证键是否存在？例如，我需要对这一行进行哪些更改或添加，例如，其他内容或类似的内容？行上If String.IsNullOrEmpty(My.Settings.username)

这是我的代码

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

Answer 1

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