我想从数据库创建一个菜单并在菜单控件中显示。
.aspx 页面中的代码：
<asp:Menu ID="Menu1" Orientation="horizontal" StaticMenuItemStyle-CssClass="menuItem"
DynamicMenuItemStyle-CssClass="menuItem" runat="server">
在 Master 的 .cs 页面中：
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
populateMenuItem();
}
}
private void populateMenuItem()
{
DataTable menuData = GetMenuData();
AddTopMenuItems(menuData);
}
/// Filter the data to get only the rows that have a
/// null ParentID (This will come on the top-level menu items)
private void AddTopMenuItems(DataTable menuData)
{
DataView view = new DataView(menuData);
view.RowFilter = "DepartmentParentID IS NULL";
foreach (DataRowView row in view)
{
//MenuItem newMenuItem = new MenuItem(row["DepartmentName"].ToString(), row["DepartmentID"].ToString());
MenuItem newMenuItem = new MenuItem(row["DepartmentName"].ToString(), row["DepartmentID"].ToString());
Menu1.Items.Add(newMenuItem);
AddChildMenuItems(menuData, newMenuItem);
}
}
//This code is used to recursively add child menu items by filtering by ParentID
private void AddChildMenuItems(DataTable menuData, MenuItem parentMenuItem)
{
DataView view = new DataView(menuData);
view.RowFilter = "DepartmentParentID=" + parentMenuItem.Value;
foreach (DataRowView row in view)
{
MenuItem newMenuItem = new MenuItem(row["DepartmentName"].ToString(), row["DepartmentID"].ToString());
parentMenuItem.ChildItems.Add(newMenuItem);
AddChildMenuItems(menuData, newMenuItem);
}
}
private DataTable GetMenuData()
{
using (SqlConnection con = new SqlConnection(conStr))
{
using (SqlCommand cmd = new SqlCommand("SELECT DepartmentID,OfficeID,DepartmentName,DepartmentParentID,IsActive,CreatedByID,CreatedDate,LastModifiedByID,LastModifiedDt FROM DepartmentMst", con))
{
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
return dt;
}
}
}
问题出在 AddTopMenuItems() 方法中，它在 Menu1.Items.Add(newMenuItem); 行显示“对象引用未设置为对象的实例”；不知道为什么？
这是 SQLSERVER2008 DepartmentMst 中的数据：
DepartmentID DepartmentName IsActive DepartmentParentID
1 HR 1 NULL
2 IT 1 NULL
3 Operations 1 NULL
4 Desktop Engineer 1 2
5 Network Engineer 1 2
6 Employee Salary 1 1
当 DepartmentParentID 为 NULL 时，它是 Main Menu，如果不为 null，则它是 Child 节点，并尊重其 Parent ID。
示例http://chandradev819.wordpress.com/2011/07/03/how-to-bind-asp-net-menu-control-with-database/
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