我已经和这个问题争吵了几天了，如果有人为我揭开光明的话，我会非常感激。
我根据另一个dorpdownlist的选择填充了一个下拉列表。只要没有发生回发，我就会看到列表正确填充但在回发后，我的下拉列表是空的。
首先，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，因为它在列表中不存在
然后我读了一些我需要设置DataValueField属性的地方，所以我做了那个摆脱错误但现在我看到回发后的空dll。 ddl的ViewStateMode设置为Enabled。
我所指的两个ddl在我的.aspx文件的Formview中定义为ddlCompanyBuyerNVListInsert和ddlCompanyNameListInsert（我只列出了Insert模式）。 根据ddlCompanyBuyerNVList中的选择，我填充了ddlCompanyNameList。
这是Page_Load背后的代码以及填充ddlCompanyNameList的函数。
受保护的子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
受保护的Sub FillCompanyNameDropDownList（ddlCompanyBuyerNamesList As DropDownList） 尝试 使用cn As New 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
受保护的Sub FillCompanyInfoFields（ddl As DropDownList） 尝试 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作为TextBox 昏暗的CoCity作为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.aspx文件中两个ddl的定义方式。
<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>
非常感谢您的回复。