我有一个关于在ASP.NET 4.0中在运行时创建控件的问题。我正在构建一个应用程序，在admin.aspx页面中，我有多个控件（DropDownLists），这些控件是使用来自Sql数据库的值动态创建的。
我知道，对于为动态创建的控件触发事件，我必须在Page_Load()或Page_Init()中创建此控件。
我的项目有一个母版页，我有一个1秒的定时器来更新时钟。这个计时器事件调用我的admin.aspx Page_Load()函数，所以我的方法创建了每1秒调用一次的动态控件 - 每秒钟都会连接到数据库，请看下面我的代码。
这样做是一个好习惯吗？你能提出一些想法吗？
protected void Page_Load(object sender, EventArgs e)
{
_SinopticBackgroundColor = ConfigurationManager.AppSettings["SinopticBackgroundColor"];
panelContent.Style.Add("background-color", _SinopticBackgroundColor);
Control c = GetControlThatCausedPostBack(this);
if (c != null)
{
if (c.ID.Equals("btnManageCategory"))
hfPageManage.Value = "category";
else if (c.ID.Equals("btnManageDevices"))
hfPageManage.Value = "device";
}
if (hfPageManage.Value.Equals("category"))
{
cbTreeViewGroup.Visible = false;
UpdateSinopticCategoryManager(TreeView1.SelectedNode); //this is the functions which loads controls from database..
}
else if (hfPageManage.Value.Equals("device"))
{
cbTreeViewGroup.Visible = true;
}
else
{
cbTreeViewGroup.Visible = false;
}
if (!Page.IsPostBack)
{
LoadFunctions(); // loads some values from database into datatables
}
else
{
}
}
这是创建控件的函数
private void UpdateSinopticCategoryManager(TreeNode node = null)
{
if (node == null)
return;
DataTable categoriiDT = null;
using (var connection = new SqlConnection(Database.ConnectionString))
{
using (var command = connection.CreateCommand())
{
command.CommandText = "SELECT * FROM categories WHERE CategoryID = @CategoryID";
command.Parameters.Add("CategoryID", node.Value);
SqlDataAdapter ad = new SqlDataAdapter(command);
DataSet ds = new DataSet("CATEGORYPROPERTIES");
connection.Open();
ad.Fill(ds);
// verificam sa avem date
if (ds.Tables.Count <= 0)
return;
if (ds.Tables[0].Rows.Count <= 0)
return;
categoriiDT = ds.Tables[0];
}
}
// generate table
Table table = new Table();
table.Style.Add("position", "relative");
table.Style.Add("top", "20px");
table.Style.Add("margin-left", "20px");
table.BorderStyle = BorderStyle.Solid;
table.BorderWidth = 1;
// header
TableHeaderRow hr = new TableHeaderRow();
for (int i = 0; i < 2; i++)
{
TableHeaderCell hc = new TableHeaderCell();
if (i > 0)
{
hc.Text = "FUNCTION";
//hc.Width = 200;
}
else
{
hc.Width = 100;
}
hr.Cells.Add(hc);
}
table.Rows.Add(hr);
var inputs = (from a in categoriiDT.Columns.Cast<DataColumn>()
where a.ColumnName.ToLowerInvariant().Contains("input")
select a.ColumnName).ToArray();
if (inputs.Count() <= 0)
return;
//rows input
for (int i = 0; i < inputs.Count(); i++)
{
TableRow tableRow = new TableRow();
for (int j = 0; j < 2; j++)
{
TableCell cell = new TableCell();
if (j > 0)
{
// adaugare 2 dropdownlist
DropDownList categList = new DropDownList();
categList.SelectedIndexChanged += new EventHandler(categList_SelectedIndexChanged);
foreach (DataRow row in functionsCategories.Rows)
{
categList.Items.Add(new ListItem(row["FunctionCategoryName"].ToString(), row["FunctionCategoryID"].ToString()));
}
DropDownList funcList = new DropDownList();
int selF = 0, selC = 0;
for (int fi = 0; fi < functions.Rows.Count; fi++)// (DataRow row in functions.Rows)
{
funcList.Items.Add(new ListItem(functions.Rows[fi]["FunctionName"].ToString(), functions.Rows[fi]["FunctionID"].ToString()));
if (functions.Rows[fi]["FunctionID"].ToString() == categoriiDT.Rows[0][inputs[i]].ToString())
{
selF = fi;
selC = Int32.Parse(functions.Rows[fi]["FunctionCategoryID"].ToString());
}
}
funcList.SelectedIndex = selF;
categList.SelectedIndex = functionsCategories.Rows.IndexOf(
(from c in functionsCategories.AsEnumerable()
where c["FunctionCategoryID"].ToString().Equals(selC.ToString())
select c).FirstOrDefault());
cell.Controls.Add(categList);
cell.Controls.Add(funcList);
}
else
{
Label label = new Label();
label.Text = "INPUT " + i.ToString();
label.Style.Add("font-weight", "bold");
cell.Controls.Add(label);
}
tableRow.Cells.Add(cell);
}
table.Rows.Add(tableRow);
}
//rows output
for (int i = 0; i < 4; i++)
{
TableRow row = new TableRow();
for (int j = 0; j < 2; j++)
{
TableCell cell = new TableCell();
if (j > 0)
{
DropDownList list = new DropDownList();
list.Width = 200;
list.Items.AddRange(GetOutputFunctions());
list.BorderColor = Color.Goldenrod;
cell.Controls.Add(list);
}
else
{
Label label = new Label();
label.Text = "OUTPUT " + i.ToString();
label.Style.Add("font-weight", "bold");
cell.Controls.Add(label);
}
row.Cells.Add(cell);
}
table.Rows.Add(row);
}
// add table to panel
panelContent.Controls.Add(table);
}
关于这一点：DropDownList categList = new DropDownList();