我有一个GridView如下：
<asp:GridView ID="gvChain" runat="server" Font-Size="Small" CellPadding="3" CellSpacing="1" GridLines="None"
AutoGenerateColumns="False">
<HeaderStyle BackColor="#CCCCCC" />
<Columns>
<asp:TemplateField HeaderText="Department" ControlStyle-Width="175px">
<EditItemTemplate>
<asp:Label ID="lblDepartment" runat="server" Text='<%# Bind("Department") %>'></asp:Label>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="lblDepartment" runat="server" Text='<%# Bind("Department") %>'></asp:Label>
</ItemTemplate>
<ControlStyle Width="175px" />
</asp:TemplateField>
<asp:TemplateField HeaderText="Manager Level 1" ControlStyle-Width="175px">
<ItemTemplate>
<asp:Label ID="lblManager1" runat="server" Text=""></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="cbManager1" runat="server"></asp:DropDownList>
</EditItemTemplate>
<ControlStyle Width="175px" />
</asp:TemplateField>
<asp:TemplateField HeaderText="Manager Level 2" ControlStyle-Width="175px">
<ItemTemplate>
<asp:Label ID="lblManager2" runat="server" Text=""></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="cbManager2" runat="server"></asp:DropDownList>
</EditItemTemplate>
<ControlStyle Width="175px" />
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:LinkButton ID="btnEdit" CommandName="Edit" runat="server" Text="Edit" CssClass="buttonStyle" CausesValidation="false"/>
</ItemTemplate>
<EditItemTemplate>
<asp:LinkButton ID="btnSave" CommandName="Update" runat="server" Text="Save" CssClass="buttonStyle" CausesValidation="false"/>
<asp:LinkButton ID="btnCancel" CommandName="Cancel" runat="server" Text="Cancel" CssClass="buttonStyle" CausesValidation="false" />
</EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:LinkButton ID="btnDelete" CommandName="Delete" runat="server" Text="Delete" CssClass="buttonStyle" CausesValidation="false" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
BoundField填充在Page_Load事件中，如下所示：
Dim dHandler As DepartmentHandler = New DepartmentHandler
Dim depts As New List(Of Department)
depts = dHandler.GetDepartmentList
gvChain.DataSource = depts.
If Not Page.IsPostBack Then
gvChain.DataBind()
End If
然后在RowDataBound事件中填充TemplateFields，如下所示：
If e.Row.RowType = DataControlRowType.DataRow Then
If e.Row.RowState = DataControlRowState.Edit Then
Dim cbManager1 As DropDownList = TryCast(e.Row.FindControl("cbManager1"), DropDownList)
Dim cbManager2 As DropDownList = TryCast(e.Row.FindControl("cbManager2"), DropDownList)
Dim eHandler As EmployeeHandler = New EmployeeHandler
' Get the list of managers
Dim mgrs As New List(Of Manager)
mgrs = eHandler.GetManagerList
cbManager1.DataSource = mgrs
cbManager2.DataSource = mgrs
cbManager1.DataValueField = "Name"
cbManager1.DataTextField = "Name"
cbManager2.DataValueField = "Name"
cbManager2.DataValueField = "Name"
cbManager1.DataBind()
cbManager2.DataBind()
' Get the department name from the label in cell 0
Dim lbl As Label = e.Row.Cells(0).FindControl("lblDepartment")
Dim dept As Department = New Department
dept.Department = lbl.Text
' Pass the department name to the getManager1/2 functions to return the correct manager for that department
Dim mgr1 As Manager = eHandler.getManager1(dept)
Dim mgr2 As Manager = eHandler.getManager2(dept)
' Upper case the manager name to search the DDLs for item
Dim mgr1Name As String = mgr1.Name.ToUpper()
Dim mgr2Name As String = mgr2.Name.ToUpper()
' Find the manager in the DDL and select
cbManager1.SelectedValue = mgr1Name
cbManager2.SelectedValue = mgr2Name
Else
' If GV isnt in edit mode then populate labels in itemtemplate with manager 1 and 2 values
Dim lblManager1 As Label = DirectCast(e.Row.FindControl("lblManager1"), Label)
Dim lblManager2 As Label = DirectCast(e.Row.FindControl("lblManager2"), Label)
Dim eHandler As EmployeeHandler = New EmployeeHandler
Dim lbl As Label = e.Row.Cells(0).FindControl("lblDepartment")
Dim dept As Department = New Department
dept.Department = lbl.Text
Dim mgr1 As Manager = eHandler.getManager1(dept)
Dim mgr2 As Manager = eHandler.getManager2(dept)
lblManager1.Text = mgr1.Name
lblManager2.Text = mgr2.Name
End If
End If
然后我在RowEditing事件中有以下内容
gvChain.EditIndex = e.NewEditIndex
gvChain.DataBind()
当GridView中只显示1条记录时，我单击编辑按钮，GridView进入编辑模式我可以使用RowUpdating事件更新该记录，这样可以正常工作。但是，如果我向GridView添加另一条记录，则单击该记录的编辑按钮会产生NullReference异常。如果我再添加另一条记录，那么第3条记录将进入编辑模式。第4条记录将再次因NullReference异常而失败，依此类推。
调试时，似乎在行索引1,3,5等上，GridView不会进入编辑模式，但在行索引0,2,4等处，GridView将切换到编辑模式。
这似乎很奇怪。可能导致GridView不在这些行上进入编辑模式的任何想法？
答案 0 :(得分：0)
行的状态可以是DataControlRowState值中的一个或组合，因此使用按位操作来确定行的状态是否包含DataControlRowState值。 here
如果使用位逻辑检查RowState属性，则RowState包含多个值（Alternate | Edit）。
尝试
If (e.Row.RowState And DataControlRowState.Edit) > 0 Then
答案 1 :(得分：0)
我通过修改getDepartmentList函数来返回Manager1和Manager 2字段，然后将它们数据绑定在我的绑定'Department'中。
然后我将RowDataBound事件修改为以下内容：
If e.Row.RowType = DataControlRowType.DataRow Then
If e.Row.RowState And DataControlRowState.Edit Then
Dim cbManager1 As DropDownList = TryCast(e.Row.FindControl("cbManager1"), DropDownList)
Dim cbManager2 As DropDownList = TryCast(e.Row.FindControl("cbManager2"), DropDownList)
Dim eHandler As EmployeeHandler = New EmployeeHandler
' Get the list of managers
Dim mgrs As New List(Of Manager)
mgrs = eHandler.GetManagerList
cbManager1.DataSource = mgrs
cbManager2.DataSource = mgrs
cbManager1.DataValueField = "Name"
cbManager1.DataTextField = "Name"
cbManager2.DataValueField = "Name"
cbManager2.DataValueField = "Name"
cbManager1.DataBind()
cbManager2.DataBind()
' Get the department name from the label in cell 0
Dim lbl As Label = e.Row.Cells(0).FindControl("lblDepartment")
Dim dept As Department = New Department
dept.Department = lbl.Text
' Pass the department name to the getManager1/2 functions to return the correct manager for that department
Dim mgr1 As Manager = eHandler.getManager1(dept)
Dim mgr2 As Manager = eHandler.getManager2(dept)
' Upper case the manager name to search the DDLs for item
Dim mgr1Name As String = mgr1.Name.ToUpper()
Dim mgr2Name As String = mgr2.Name.ToUpper()
' Find the manager in the DDL and select
cbManager1.SelectedValue = mgr1Name
cbManager2.SelectedValue = mgr2Name
End If
End If