几天来我一直在与这个问题作斗争，如果有人能为我提供一些启示，我将不胜感激。
我正在根据来自另一个 dorpdownlist 的选择填充一个下拉列表。只要没有回发发生，我就会看到列表被正确填充，但是在回发之后，我的下拉列表是空的。
起初，我试图手动设置 ddl 的 Text 属性，但它一直给我以下错误：
System.ArgumentOutOfRangeException：..ddl 有一个无效的 SelectedValue，因为它不存在于列表中
然后我在某处读到我需要设置 DataValueField 属性，所以我做了消除错误的操作，但现在我在回发后看到了空的 dll。
ddl 的 ViewStateMode 设置为 Enabled。
我所指的两个 ddls 在我的 .aspx 文件的 Formview 中定义为 ddlCompanyBuyerNVListInsert 和 ddlCompanyNameListInsert（我只列出了插入模式）。基于在 ddlCompanyBuyerNVList 中所做的选择，我正在填充 ddlCompanyNameList。
下面是 Page_Load 的代码和填充 ddlCompanyNameList 的函数。
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) 处理 Me.Load
If Not IsPostBack Then
If NavHelper.User.UserName = "" Then
Dim UserIP As String
Dim UserLogin As String
Dim UserEmail As String
UserIP = HttpContext.Current.Request.UserHostAddress
UserLogin = HttpContext.Current.Session("Username")
UserEmail = HttpContext.Current.Session("Email")
GetUserInfo()
CurrentRFQ = Nothing
If NavHelper.RFQ.ID = -1 Then
formview_RFQ.ChangeMode(FormViewMode.Insert)
tabpanelCustomerParts.Visible = False
tabpanelDocuments.Visible = False
tabpanelReviews.Visible = False
tabpanelRFQReviewHistory.Visible = False
listview_CustomerParts.Dispose()
Else
formview_RFQ.ChangeMode(FormViewMode.Edit)
listview_ReviewContracts_Initial.EditIndex = 0
SessionHelper.CurrentObject = TAA.Library.RFQ.GetObject(NavHelper.RFQ.ID)
mRFQ = DirectCast(SessionHelper.CurrentObject, TAA.Library.RFQ)
Dim UserdeptTotal As Long
UserdeptTotal = HttpContext.Current.Session("DepartmentTotal")
If formview_RFQ.FindControl("ddlCompanyBuyerNVList") IsNot Nothing Then
Dim ddl As DropDownList = DirectCast(formview_RFQ.FindControl("ddlCompanyBuyerNVList"), DropDownList)
FillCompanyNameDropDownList(ddl)
End If
tabpanelCustomerParts.Visible = True
tabpanelDocuments.Visible = True
tabpanelReviews.Visible = True
tabpanelRFQReviewHistory.Visible = True
If NavHelper.RFQ.Copy = True Then
SetModifyCopy()
End If
End If
Else 'IsPostBack
datasource_BuyerNVList.Dispose()
datasource_RFQ.DataBind()
datasource_RFQNote.DataBind()
Dim ddl As DropDownList
If (formview_RFQ.CurrentMode = FormViewMode.Insert) Then
ddl = DirectCast(formview_RFQ.FindControl("ddlCompanyBuyerNVListInsert"), DropDownList)
ElseIf formview_RFQ.FindControl("ddlCompanyBuyerNVList") IsNot Nothing Then
ddl = DirectCast(formview_RFQ.FindControl("ddlCompanyBuyerNVList"), DropDownList)
End If
FillCompanyNameDropDownList(ddl)
End If
End If
End Sub
Protected Sub FillCompanyNameDropDownList(ddlCompanyBuyerNamesList As DropDownList) 尝试使用 cn 作为新的 SqlClient.SqlConnection(DB.RFQconnection) cn.Open()
Using cm As SqlClient.SqlCommand = cn.CreateCommand
cm.CommandType = CommandType.StoredProcedure
cm.CommandText = "GetCompanyNamesForThisBuyer"
cm.Parameters.AddWithValue("@BuyerName", (ddlCompanyBuyerNamesList.SelectedItem.Text))
Dim ddlCompanyNamesList As DropDownList
If (formview_RFQ.CurrentMode = FormViewMode.Insert) Then
ddlCompanyNamesList = DirectCast(formview_RFQ.FindControl("ddlCompanyNameListInsert"), DropDownList)
Else
ddlCompanyNamesList = DirectCast(formview_RFQ.FindControl("ddlCompanyNameList"), DropDownList)
End If
Using r As New SCF.Data.SafeDataReader(cm.ExecuteReader)
ddlCompanyNamesList.Items.Clear()
ddlCompanyNamesList.Items.Add(New ListItem("Select Company"))
While r.Read
Dim li As ListItem = New ListItem()
li.Value = SCF.Data.SafeData.SafeInteger(r("CompanyBuyerId"))
li.Text = SCF.Data.SafeData.SafeString(r("CompanyName"))
ddlCompanyNamesList.Items.Add(li)
End While
End Using
cm.Dispose()
cn.Close()
' if more than one entry found, clear the company info fields until a selection is made
If ddlCompanyNamesList.Items.Count > 2 Then 'because we've added a "Select Company" as the first item
ClearCompanyInfoFields() ' company fields are text boxes that get cleared here
ddlCompanyNamesList.SelectedIndex = 0
End If
ddlCompanyNamesList.Enabled = True
If ddlCompanyNamesList.Items.Count = 2 Then ' if only one entry found populate the compny info with that one entry's selection
ddlCompanyNamesList.SelectedIndex = 1
FillCompanyInfoFields(ddlCompanyNamesList)
ElseIf ddlCompanyNamesList.Items.Count = 0 Then ' if nothing found use the buyer list to populate company info fields
ddlCompanyNamesList.Items.Clear()
FillCompanyInfoFields(ddlCompanyBuyerNamesList)
ddlCompanyNamesList.Enabled = False
End If
End Using
End Using
Catch ex As System.Exception
SetErrorPanel("An error occured during FillCompanyNameDropDownList.")
Dim err As New HealthMonitoringCustomEvents.ErrorEvent("An error occured during FillCompanyNameDropDownList", Me, ex)
err.Raise()
End Try
End Sub
Protected Sub FillCompanyInfoFields(ddl As DropDownList) Try Dim BuyerTitle As TextBox Dim BuyerEmail As TextBox Dim BuyerPhone As TextBox Dim BuyerExt As TextBox Dim BuyerMobile As TextBox Dim BuyerFax As TextBox Dim CoAddr As TextBox Dim CoCity As TextBox Dim CoState As TextBox Dim CoZip As TextBox
If (formview_RFQ.CurrentMode = FormViewMode.Insert) Then
buyerTitle = DirectCast(formview_RFQ.FindControl("txtBuyerTitleInsert"), TextBox)
buyerEmail = DirectCast(formview_RFQ.FindControl("txtBuyerEmailInsert"), TextBox)
buyerPhone = DirectCast(formview_RFQ.FindControl("txtBuyerPhoneNumberInsert"), TextBox)
buyerExt = DirectCast(formview_RFQ.FindControl("txtExtInsert"), TextBox)
buyerMobile = DirectCast(formview_RFQ.FindControl("txtBuyerMobileNumberInsert"), TextBox)
buyerFax = DirectCast(formview_RFQ.FindControl("txtBuyerFaxNumberInsert"), TextBox)
CoAddr = DirectCast(formview_RFQ.FindControl("txtCompanyAddressInsert"), TextBox)
CoCity = DirectCast(formview_RFQ.FindControl("txtCompanyCityInsert"), TextBox)
CoState = DirectCast(formview_RFQ.FindControl("txtCompanyStateCodeInsert"), TextBox)
CoZip = DirectCast(formview_RFQ.FindControl("txtCompanyZipCodeInsert"), TextBox)
Else
buyerTitle = DirectCast(formview_RFQ.FindControl("txtBuyerTitle"), TextBox)
buyerEmail = DirectCast(formview_RFQ.FindControl("txtBuyerEmail"), TextBox)
buyerPhone = DirectCast(formview_RFQ.FindControl("txtBuyerPhoneNumber"), TextBox)
buyerExt = DirectCast(formview_RFQ.FindControl("txtExt"), TextBox)
buyerMobile = DirectCast(formview_RFQ.FindControl("txtBuyerMobileNumber"), TextBox)
buyerFax = DirectCast(formview_RFQ.FindControl("txtBuyerFaxNumber"), TextBox)
CoAddr = DirectCast(formview_RFQ.FindControl("txtCompanyAddress"), TextBox)
CoCity = DirectCast(formview_RFQ.FindControl("txtCompanyCity"), TextBox)
CoState = DirectCast(formview_RFQ.FindControl("txtCompanyStateCode"), TextBox)
CoZip = DirectCast(formview_RFQ.FindControl("txtCompanyZipCode"), TextBox)
End If
Using cn As New SqlClient.SqlConnection(DB.RFQconnection)
cn.Open()
Using cm As SqlClient.SqlCommand = cn.CreateCommand
cm.CommandType = CommandType.StoredProcedure
cm.CommandText = "GetBuyerCompanyInfo"
cm.Parameters.AddWithValue("@companyBuyerId", (ddl.SelectedValue))
Using r As New SCF.Data.SafeDataReader(cm.ExecuteReader)
' populate company information fields in CurrentRFQ
While r.Read
CurrentRFQ.CompanyID = SCF.Data.SafeData.SafeString(r(0))
CurrentRFQ.CompanyBuyerId = SCF.Data.SafeData.SafeString(r(7))
ddl.DataValueField = SCF.Data.SafeData.SafeString(r(1))
CoAddr.Text = SCF.Data.SafeData.SafeString(r(2))
CoCity.Text = SCF.Data.SafeData.SafeString(r(4))
CoState.Text = SCF.Data.SafeData.SafeString(r(5))
CoZip.Text = SCF.Data.SafeData.SafeString(r(6))
buyerTitle.Text = SCF.Data.SafeData.SafeString(r(9))
buyerEmail.Text = SCF.Data.SafeData.SafeString(r(10))
buyerPhone.Text = SCF.Data.SafeData.SafeString(r(11))
buyerExt.Text = SCF.Data.SafeData.SafeString(r(12))
buyerMobile.Text = SCF.Data.SafeData.SafeString(r(13))
buyerFax.Text = SCF.Data.SafeData.SafeString(r(14))
End While
End Using
cm.Dispose()
cn.Close()
End Using
End Using
Catch ex As System.Exception
SetErrorPanel("An error occured during FillCompanyInfoFields.")
Dim err As New HealthMonitoringCustomEvents.ErrorEvent("An error occured during FillCompanyInfoFields", Me, ex)
err.Raise()
End Try
End Sub
以下是在 .aspx 文件中定义两个 ddls 的方式。
<td> <asp:DropDownList ID="ddlCompanyBuyerNVListInsert" runat="server"
AppendDataBoundItems="true" AutoPostBack="true" CssClass="Input"
DataSourceID="datasource_BuyerNVlist" DataTextField="Key" DataValueField="Value"
OnSelectedIndexChanged="ddlCompanyBuyerNVListInsert_SelectedIndexChanged"
ViewStateMode="Enabled" Width="205px"> <asp:ListItem Selected="True" Text="Select
Buyer" Value="0" /> </asp:DropDownList> </td> <td></td> <td class="style4"> Company:
</td> <td>
<asp:DropDownList ID="ddlCompanyNameListInsert" runat="server"
AppendDataBoundItems="True" AutoPostBack="True" CssClass="Input"onselectedindexchanged="ddlCompanyNameListInsert_SelectedIndexChanged"
ViewStateMode="Enabled" Enabled="False"> </asp:DropDownList> </td>
非常感谢你的回复。