我有一个动态创建的数据绑定网格视图。数据源基于多个DropDownLists返回一个对象（对象的类型不同）。根据对象的类型，GridView必须显示仅特定于对象的某些字段。此外，还有一个DropDownList，其SelectedValue决定从GridView添加/排除对象的哪些列。
这是一个创建GridView的方法（我用VB.NET编写，但C＃也非常受欢迎）：
Private Sub CreateGridView()
Dim gv As New GridView
With gv
.AllowSorting = True
.AutoGenerateColumns = False
.CssClass = "gv"
.EmptyDataText = "The list is empty"
.ID = "gv"
.ShowFooter = True
.AlternatingRowStyle.Wrap = False
.EditRowStyle.Wrap = False
.FooterStyle.Wrap = False
.HeaderStyle.Wrap = False
.SortedAscendingCellStyle.CssClass = "sortAscCell"
.SortedAscendingHeaderStyle.CssClass = "sortAscHeader"
.SortedDescendingCellStyle.CssClass = "sortDescCell"
.SortedDescendingHeaderStyle.CssClass = "sortDescHeader"
AddHandler .RowDataBound, AddressOf gv_RowDataBound
AddHandler .DataBound, AddressOf gv_DataBound
AddHandler .RowUpdating, AddressOf gv_RowUpdating
.DataSource = odsEquipment.Select
.DataKeyNames = {"equipmentID"}
End With
For Each item As Dictionary In odsDictionary.Select
If ddlStages.SelectedValue <> "" Then
If ddlStages.SelectedValue >= item.stage_id Then
Dim tf As New TemplateField()
tf.SortExpression = item.col
tf.HeaderTemplate = New GridViewTemplate(item.title, item.col)
tf.ItemTemplate = New GridViewTemplate(DataControlRowType.DataRow, item.col, item.ctrlType, item.length)
tf.FooterTemplate = New GridViewTemplate(DataControlRowType.Footer, item.col, item.ctrlType, item.length)
gv.Columns.Add(tf)
End If
End If
Next
gv.DataBind()
divGV.Controls.Add(gv)
End Sub
GridView始终处于编辑模式，这意味着它的ItemTemplate是TexBox / DropDownList / CheckBox。这是一个ITemplate类：
Imports System.Data
Public Class GridViewTemplate
Implements ITemplate
Private templateType As DataControlRowType
Private title As String
Private columnBinding As String
Private ctrlType As String
Private length As Integer
Public Sub New(ByVal vTitle As String, vColumnBinding As String)
templateType = DataControlRowType.Header
title = vTitle
columnBinding = vColumnBinding
End Sub
Public Sub New(ByVal type As DataControlRowType, ByVal vColumnBinding As String, ByVal vCtrlType As String, vLength As Integer)
templateType = type
columnBinding = vColumnBinding
ctrlType = vCtrlType
length = vLength
End Sub
Private Sub InstantiateIn(container As Control) Implements ITemplate.InstantiateIn
Select Case templateType
Case DataControlRowType.Header
Dim lb As New LinkButton()
lb.ID = "lb" + columnBinding
lb.CommandName = "Sort"
lb.CommandArgument = columnBinding
lb.Text = title
container.Controls.Add(lb)
Exit Select
Case DataControlRowType.DataRow
If ctrlType = "Label" Then
Dim lbl = New Label()
lbl.ID = "lbl" + columnBinding
AddControl(lbl, container)
ElseIf ctrlType = "TextBox" Then
Dim tb As New TextBox
tb.ID = "tb" + columnBinding
tb.MaxLength = length
AddControl(tb, container)
ElseIf ctrlType = "CheckBox" Then
Dim cb = New CheckBox()
cb.ID = "cb" + columnBinding
AddControl(cb, container)
ElseIf ctrlType = "DropDownList" Then
Dim ddl = New DropDownList()
ddl.ID = "ddl" + columnBinding
AddControl(ddl, container)
End If
Exit Select
Case DataControlRowType.Footer
If ctrlType = "Label" Then
Dim tbFrom As New TextBox()
tbFrom.ID = "tb" + columnBinding + "From"
container.Controls.Add(tbFrom)
Dim tbTo As New TextBox()
tbTo.ID = "tb" + columnBinding + "From"
container.Controls.Add(tbTo)
ElseIf ctrlType = "TextBox" Then
Dim tb As New TextBox
tb.ID = "tb" + columnBinding
tb.MaxLength = length
container.Controls.Add(tb)
ElseIf ctrlType = "CheckBox" Then
Dim cb = New CheckBox()
cb.ID = "cb" + columnBinding
container.Controls.Add(cb)
ElseIf ctrlType = "DropDownList" Then
Dim ddl = New DropDownList()
ddl.ID = "ddl" + columnBinding
AddControl(ddl, container)
End If
Exit Select
Case Else
Exit Select
End Select
End Sub
Private Sub AddControl(ctrl As Control, container As Control)
AddHandler ctrl.DataBinding, AddressOf OnDataBinding
container.Controls.Add(ctrl)
End Sub
Private Sub OnDataBinding(ByVal sender As Object, ByVal e As EventArgs)
If sender.GetType = GetType(Label) Then
Dim lb As Label = DirectCast(sender, Label)
Dim container As GridViewRow = DirectCast(lb.NamingContainer, GridViewRow)
lb.Text = DataBinder.Eval(container.DataItem, columnBinding).ToString
ElseIf sender.GetType = GetType(TextBox) Then
Dim tb As TextBox = DirectCast(sender, TextBox)
Dim container As GridViewRow = DirectCast(tb.NamingContainer, GridViewRow)
tb.Text = DataBinder.Eval(container.DataItem, columnBinding).ToString
ElseIf sender.GetType = GetType(CheckBox) Then
Dim cb As CheckBox = DirectCast(sender, CheckBox)
Dim container As GridViewRow = DirectCast(cb.NamingContainer, GridViewRow)
cb.Checked = DataBinder.Eval(container.DataItem, columnBinding).ToString
ElseIf sender.GetType = GetType(DropDownList) Then
Dim ddl As DropDownList = DirectCast(sender, DropDownList)
Dim container As GridViewRow = DirectCast(ddl.NamingContainer, GridViewRow)
If columnBinding = "criticalityRating" Then
ddl.Items.Add("")
For i = 1 To 4
ddl.Items.Add(i)
Next
ElseIf columnBinding = "property_id" Then
For Each p As PropertyMP In PropertyMPDB.GetProperties
ddl.Items.Add(New ListItem(p.propertyMP, p.property_id))
Next
End If
If templateType = DataControlRowType.DataRow Then
ddl.SelectedValue = DataBinder.Eval(container.DataItem, columnBinding).ToString
End If
End If
End Sub
End Class
DropDownLists绑定到自己的ObjectDataSources并在标记中创建。
据我所知，必须在Page.Init中的每个回发中实例化GridView。 Page.Load因创建gridview而迟到，因为它不会维护ViewState，也无法更新。但是，当我在Init上创建它时，DropDownLists尚未创建或DataBound尚未创建，因此没有选定的值。我尝试在他们的Inits上填充DropDownLists而不是将它们绑定到DataSource，但是当我更改SelectedValue时它会抛出ViewState错误。
当我在Load上创建GridView时，一切都很完美，除了最重要的部分，更新......
任何人都可以帮我弄清楚我在哪里初始化/绑定GridView / DropDownLists？我已经三天苦苦挣扎，在这里绝望了:(
答案 0 :(得分：1)
找不到解决方案但找到了解决方法。
GridView创建OnInit，在GridView Init上添加字段。在所有DropDownLists都是DataBound之后，ObjectDataSource从DropDownLists接收其参数。
有一个DropDownList，它负责返回的Object类型。更改SelectedValue后，重新启动DropDownList，ObjectDataSource仍具有旧值并返回错误的对象。这就是错误所在 - 将GridView绑定到具有错误字段的Object。而不是这个，我使用QueryString并做了一个回发。在下一次加载时，ObjectDataSource返回与GridView字段匹配的正确对象。从那里一切都很顺利。