【发布时间】：2011-12-06 17:39:05
【问题描述】：
所以我有一个包含gridview 的页面，girdview 通过Web 服务从objectdatasource 获取它的数据。它包含 2 列与项目模板。对于处于编辑模式下的每个模板，包含存储在 edititemtemplates 下的下拉列表。
一切似乎都正常，除了当我处于编辑模式并触发更新事件时，我的下拉列表会抛出空引用错误。经过进一步调查，这似乎是由于代码隐藏思维无法找到 dropdroplists 造成的。此外，在挖掘调试器时，下拉列表似乎甚至不存在。 虽然，在我的页面上，当处于编辑模式时会显示下拉列表，但代码隐藏无法找到这些控件。
我的猜测是我将 gridview 绑定在错误的位置，或者绑定本身不正确。
我想知道的是，为什么会出现这种情况，我该如何解决？ 如果有人能告诉我我的绑定是否正确，我也将不胜感激。
您将在下面找到我的 gridview 代码及其代码隐藏代码。
网格视图：
<asp:GridView ID="GridViewHolder"
runat="server"
AllowPaging="True"
AutoGenerateColumns="False"
BackColor="Transparent"
BorderColor="#999999"
BorderStyle="Ridge"
BorderWidth="3px"
CellPadding="4"
CellSpacing="2"
DataSourceID="MachineDataSet"
ForeColor="Black"
HeaderStyle-HorizontalAlign="Center"
HorizontalAlign="Center"
RowStyle-HorizontalAlign="Center"
Width="796px"
OnRowUpdating="GridViewHolder_Updating"
OnRowCancelingEdit="GridViewHolder_Canceling"
OnRowEditing="GridViewHolder_Editing"
OnRowCommand="GridViewHolder_RowCommand"
EnableViewState="False">
<RowStyle BackColor="Transparent"
HorizontalAlign="Center" />
<Columns>
<asp:TemplateField HeaderText="ID"
SortExpression="ID"
Visible="False">
<ItemTemplate>
<asp:Label ID="MachineIDLabel"
runat="server"
Text='<%# Bind("ID") %>'
Visible="false"></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="MachineIDText"
runat="server"
Text='<%# Bind("ID") %>'>
</asp:TextBox>
</EditItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="SiteName"
HeaderText="Site Name"
SortExpression="SiteName"
ReadOnly="true" />
<asp:BoundField DataField="Name"
HeaderText="Machine Name"
ReadOnly="true"
SortExpression="Name" />
<asp:TemplateField HeaderText="Machine Type"
SortExpression="MachineType">
<ItemTemplate>
<asp:Label ID="MachineTypeLabel"
runat="server"
Text='<%# Bind("MachineType") %>'>
</asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="MachineTypeDropDown"
runat="server"
AppendDataBoundItems="True"
Height="21px"
Width="217px"
DataSourceID="GetMachineType"
DataTextField="Name"
DataValueField="ID">
<asp:ListItem Enabled="true"
Text="Select a Machine Type."
Value="empty">
</asp:ListItem>
</asp:DropDownList>
</EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Machine Model" SortExpression="MachineModel">
<ItemTemplate>
<asp:Label ID="MachineModelLabel"
runat="server"
Text='<%# Bind("MachineModel") %>'>
</asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="MachineModelDropDown"
runat="server"
AppendDataBoundItems="True"
Height="21px" Width="217px"
DataSourceID="GetMachineModel"
DataTextField="Name"
DataValueField="ID">
<asp:ListItem Enabled="true"
Text="Select a Machine Model."
Value="empty">
</asp:ListItem>
</asp:DropDownList>
</EditItemTemplate>
</asp:TemplateField>
<asp:CommandField ButtonType="Button"
ShowEditButton="True"
CausesValidation="false" >
<ItemStyle HorizontalAlign="Center"
Wrap="True" />
</asp:CommandField>
</Columns>
<FooterStyle BackColor="Transparent" />
<PagerStyle BackColor="Transparent"
ForeColor="Black"
HorizontalAlign="Left" />
<SelectedRowStyle BackColor="Transparent"
Font-Bold="True"
ForeColor="White" />
<HeaderStyle BackColor="Black"
Font-Bold="True"
ForeColor="White"
HorizontalAlign="Center" />
</asp:GridView>
代码隐藏：
页面加载方法：
/// <summary>
/// Handles the Load event of the Page control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param>
protected void Page_Load(object sender, EventArgs e)
{
logger.Debug("Entering Page_Load");
Boolean loginRequired = true;
// If no login is required set the session variable and proceed to the main page.
string str = ConfigurationManager.AppSettings["i0"] as string;
if (!string.IsNullOrEmpty(str))
{
string flag = MyExtensions.Decrypt(str, true);
if ("false".Equals(flag, StringComparison.InvariantCultureIgnoreCase))
loginRequired = true;
else
{
loginRequired = false;
// User logged in so check the permissions.
UserInfo user = (UserInfo)Session[Constants.LOGGEDINUSER];
if (null == user)
loginRequired = true;
else
{
string groupId = user.GroupId;
if (string.IsNullOrEmpty(groupId))
loginRequired = true;
else if (!"Admins".Equals(user.GroupId) && !"Engineer".Equals(user.GroupId))
loginRequired = true;
}
}
}
if (!Page.IsPostBack)
{
Control ctrl = MyExtensions.FindControlRecursive(this, "CommissioningLoginPanel");
Panel loginPanel = null;
Panel contentPanel = null;
if (null != ctrl)
{
loginPanel = (Panel)ctrl;
ctrl = MyExtensions.FindControlRecursive(this, "CommissioningPanel");
if (null != ctrl)
contentPanel = (Panel)ctrl;
}
if (loginRequired)
{
if (null != loginPanel)
loginPanel.Visible = true;
if (null != contentPanel)
contentPanel.Visible = false;
}
else
{
if (null != loginPanel)
loginPanel.Visible = false;
if (null != contentPanel)
contentPanel.Visible = true;
}
}
BindData();
logger.Debug("Leaving Page_Load");
}
gridview 事件：
/// <summary>
/// Handles the Click event of the update button under edit in the gridview control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The <see cref="System.Web.UI.WebControls.GridViewUpdateEventArgs"/> instance containing the event data.</param>
protected void GridViewHolder_Updating(object sender, GridViewUpdateEventArgs e)
{
logger.Debug("Entering GridviewHolder_Updating");
int machineid;
string machineid1;
string machineTypeid;
string machineModelid;
//retrieve and set the data
GridViewHolder.EditIndex = e.RowIndex;
try
{
GridViewRow row = (GridViewRow)GridViewHolder.Rows[e.RowIndex];
TextBox mID = row.FindControl("MachineIDText") as TextBox;
DropDownList mType = row.FindControl("MachineTypeDropDown") as DropDownList;
DropDownList mModel = row.FindControl("MachineModelDropDown") as DropDownList;
machineid1 = mID.Text;
machineid = Convert.ToInt32(machineid1);
machineTypeid = mType.SelectedValue;
machineModelid = mModel.SelectedValue;
try
{
if (machineTypeid != "empty" || machineModelid != "empty")
{
if (machineTypeid != "empty")
{
inputsService.UpdateMachineTypes(machineid, machineTypeid);
}
if (machineModelid != "empty")
{
inputsService.UpdateMachineModels(machineid, machineModelid);
}
UpdateSucceed.Visible = true;
logger.Debug("Updating - Database successfully updated!");
}
else
{
UpdateFail.Visible = true;
logger.Debug("Updating - Database had no data selected to be updated.");
}
}
catch (Exception ex)
{
logger.ErrorFormat("Updating - Failed to update the table, ex = {0}", ex);
}
}
catch (Exception ex)
{
logger.ErrorFormat("Updating.gathering page controls - Failed to update the table, ex = {0}", ex);
}
logger.Debug("Leaving GridViewHolder_Updating");
}
/// <summary>
/// Handles the Click event of the cancel button under edit in the gridview control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The <see cref="System.Web.UI.WebControls.GridViewCancelEditEventArgs"/> instance containing the event data.</param>
protected void GridViewHolder_Canceling(object sender, GridViewCancelEditEventArgs e)
{
logger.Debug("Entering GridViewHolder_Canceling");
//reset the edit index
GridViewHolder.EditIndex = -1;
//Bind data to GridViewHolder
BindData();
logger.Debug("Leaving GridViewHolder_Canceling");
}
/// <summary>
/// Handles the Click event of the cancel button under edit in the gridview control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The <see cref="System.Web.UI.WebControls.GridViewEditEventArgs"/> instance containing the event data.</param>
protected void GridViewHolder_Editing(object sender, GridViewEditEventArgs e)
{
logger.Debug("Entering GridViewHolder_Editing");
//set the edit index to a new value
GridViewHolder.EditIndex = e.NewEditIndex;
//Bind data to gridviewholder
BindData();
logger.Debug("Leaving GridViewHolder_Editing");
}
BindData 方法：
private void BindData()
{
logger.Debug("Entering DataBind");
GridViewHolder.DataSource = Session["MachineTable"];
GridViewHolder.DataBind();
logger.Debug("Leaving DataBind");
}
非常感谢任何帮助或建议。
谢谢
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