ASP.NET w/ VB.NET - Winforms 到 Web - NullReferenceException 字符串拆分/字符串生成器错误

Question

背景：我有一个 winForm 应用程序，它根据提供的信息在数据库中注册用户，自动生成随机密码和用户名，并通过电子邮件向用户发送一个链接，以根据所选的营销公司进行申请。

问题：

• 当用户单击“发送邀请”并在除调试中的捆绑列表框之外的所有字段中输入数据时，会引发 NullReferenceException 错误，突出显示该行： Dim MChort As String = Trim(splitMC(0))

如何解决此问题

以下是 Web 应用程序的屏幕截图：

以下是 default.asx.vb 中的 Send_Button_Click 方法的代码：

Private Sub Send_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Send_Button.Click

    'TODO Add code to validate that all selections that are reaquired are met.
    'ccemail and the additional message are not required
    Dim firstname As String = txtFirstName.Text
    Dim lastname As String = txtLastName.Text
    Dim ccEmail As String = txtccEmail.Text

    Dim sb As New StringBuilder

    sb.AppendLine("<?xml version=""1.0"" encoding=""utf-8""?>")
    sb.AppendLine("<root>")
    sb.AppendLine("<MarketingCompany>")
    sb.AppendLine("<MarketingCompanyName>")

    ''Get Marketing Company Short Name
    Dim splitMC As String() = Split(marketingCo.SelectedItem, "|")
    Dim MCShort As String = Trim(splitMC(0))
    sb.AppendLine(String.Format("<MCNAme>{0}</MCNAme>", MCShort))


    'sb.AppendLine(String.Format("<MCNAme>{0}</MCNAme>", My.Settings.MarketingCompanyShortName))

    sb.AppendLine(String.Format("<ccEmail>{0}</ccEmail>", txtccEmail.Text))
    sb.AppendLine(String.Format("<emailMessage>{0}</emailMessage>", txtMessage.Text))
    sb.AppendLine(String.Format("<MarketerName>{0}</MarketerName>", txtMarketerName.Text))
    sb.AppendLine("<agent>")
    sb.AppendLine(String.Format("<FirstName>{0}</FirstName>", txtFirstName.Text))
    sb.AppendLine(String.Format("<LastName>{0}</LastName>", txtLastName.Text))
    sb.AppendLine(String.Format("<Email>{0}</Email>", txtEmail.Text))
    sb.AppendLine("<CRMGuid>123456</CRMGuid>")

    Dim spltBundles() As String

    For Each item In bundles.Items
        If Trim(item) <> "" Then
            spltBundles = Split(item, "|")
            sb.AppendLine("<ContractingOpportunity>")
            sb.AppendLine(String.Format("<Carrier>{0}</Carrier>", Trim(spltBundles(0))))
            sb.AppendLine(String.Format("<ContractingOpportunityName>{0}</ContractingOpportunityName>", Trim(spltBundles(1))))
            sb.AppendLine("</ContractingOpportunity>")
        End If
    Next

    sb.AppendLine("</agent>")
    sb.AppendLine("</MarketingCompanyName>")
    sb.AppendLine(" </MarketingCompany>")
    sb.AppendLine(" </root>")
    Dim xmlStr = sb.ToString


    Dim int1 As Boolean = proxy.AddContractOpportunity(xmlStr.ToString, "test", "test")

    MsgBox("aComp Invitation Sent! :)")


End Sub

Answer 1

对于第一个问题，您可以使用 lbCarriers 的 OnSelectedIndexChanged 事件。

关于提交时缺少数据的问题，您应该在提交的页面上使用某种验证。 ASP.Net 包含一组验证控件，使工作变得简单。在最简单的级别上，您可以将表单控件设置为必需，这将允许表单在触发代码隐藏事件之前提示用户填写所有必填字段。

Answer 2

我重写了以下代码区域以消除错误：

    ''Get Marketing Company Short Name
    Dim splitMC As String() = marketingCo.SelectedItem.ToString().Split("|")
    Dim MCShort As String = Trim(splitMC(0))


Protected Sub lbCarriers_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles lbCarriers.SelectedIndexChanged
    Dim splt() As String
    Dim ac1 As Array
    bundles.Items.Clear()
    Dim item As ListItem = lbCarriers.SelectedItem
    splt = item.ToString().Split("|")
    ac1 = proxy.GetContractingBundles("test", "test", Trim(splt(0)))
    For Each Pitem In ac1
        bundles.Items.Add(Trim(splt(2)) & " | " & Pitem.FormBundleName)
    Next
End Sub