Custom user control data source
Question
I have a custom control that has a DropDownList inside and it's created by CreateUserControl. I'm saving data source directly to dropdown control. After page postbacked my binded data disappear. Should i save/restore my binded data myself in some tricky way?
public class EnumDropDownList : UserControl
{
private readonly DropDownList _ddlSelector;
private Dictionary<long, string> _dataSource;
public EnumDropDownList()
{
_ddlSelector = new DropDownList();
_dataSource = new Dictionary<long, string>();
}
public object DataSource
{
set
{
// datasource logic
}
}
public long SelectedValue
{
get { return Convert.ToInt64(_ddlSelector.SelectedValue); }
set { _ddlSelector.SelectedValue = value.ToString(); }
}
public override void DataBind()
{
_ddlSelector.DataSource = _dataSource;
_ddlSelector.DataTextField = "Value";
_ddlSelector.DataValueField = "Key";
_ddlSelector.DataBind();
base.DataBind();
}
[PermissionSet(SecurityAction.Demand, Name = "Execution")]
protected override void CreateChildControls()
{
Controls.Add(_ddlSelector);
}
}
3 answers
solution1
0 2013-04-02 17:45:34
In some cases I have saved the dataset in a session variable. Whicn can then be referenced after postbacks. Something like this:
Session.Add("dataSource", _dataSource);//create the session variable
Then you can reference it, depending on the type the data source is (in example I used a datable)
_ddlSelector.DataSource = (DataTable)Session["dataSource"];
solution2
0 ACCPTED 2013-04-02 18:26:24
You code is combination of UserControl and CustomServerControl .
It could have be a lot easier if you implement one instead of combination.
I created two controls - UserControl and CustomServerControl .
UserControl
Place the dropdownlist to ASPX instead of loading dymaiclally. If you load dynamically, you'll have to take care of persistence of control.
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="EnumDropDownList.ascx.cs"
Inherits="WebApplication2010.EnumDropDownList" %>
<asp:DropDownList runat="server" ID="DropDownList1" />
public partial class EnumDropDownList : System.Web.UI.UserControl
{
private Dictionary<long, string> _dataSource;
public EnumDropDownList()
{
_dataSource = new Dictionary<long, string>();
}
public Dictionary<long, string> DataSource
{
set { _dataSource = value; }
}
public long SelectedValue
{
get { return Convert.ToInt64(DropDownList1.SelectedValue); }
set { DropDownList1.SelectedValue = value.ToString(); }
}
public override void DataBind()
{
DropDownList1.DataSource = _dataSource;
DropDownList1.DataTextField = "Value";
DropDownList1.DataValueField = "Key";
DropDownList1.DataBind();
base.DataBind();
}
}
Custom Server Control (it is a lot easier to implement for your case)
It basically inherits DropDownList web control.
public class MyDropDownList : DropDownList
{
public long SelectedInt64Value
{
get { return Convert.ToInt64(SelectedValue); }
set { SelectedValue = value.ToString(); }
}
public Dictionary<long, string> DataSource
{
get { return (Dictionary<long, string>)ViewState["DataSource"]; }
set { ViewState["DataSource"] = value; }
}
public override void DataBind()
{
foreach (var item in DataSource)
Items.Add(new ListItem(item.Value, item.Key.ToString()));
base.DataBind();
}
}
Usage
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm5.aspx.cs" Inherits="WebApplication2010.WebForm5" %>
<%@ Register Src="EnumDropDownList.ascx" TagName="EnumDropDownList" TagPrefix="uc1" %>
<%@ Register TagPrefix="asp" Namespace="WebApplication2010" Assembly="WebApplication2010" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<uc1:EnumDropDownList ID="EnumDropDownList1" runat="server" />
<asp:Button runat="server" ID="Button1" Text="Submit" OnClick="Button1_Click" />
<asp:MyDropDownList id="MyDropDownList1" runat="server" />
</form>
</body>
</html>
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
Dictionary<long, string> dataSource = new Dictionary<long, string>();
dataSource.Add(1, "One");
dataSource.Add(2, "Two");
EnumDropDownList1.DataSource = dataSource;
EnumDropDownList1.DataBind();
MyDropDownList1.DataSource = dataSource;
MyDropDownList1.DataBind();
}
}
solution3
0 2013-04-03 07:52:22
THis Is aspx file :
<telerik:RadComboBox ID="cmbCurrency" runat="server" Width="200px" MaxHeight="200px"
EmptyMessage="Select a currency" AutoPostBack="true" Filter="Contains" EnableLoadOnDemand="true">
</telerik:RadComboBox>
This is code Behind :
if (!IsPostBack)
{
popCurrencyName();
}
public void popCurrencyName()
{
DataTable dtCurrency = objCurrencyBAL.getCurrency(long.MinValue);
if (dtCurrency.Rows.Count > 0)
{
cmbCurrency.DataSource = dtCurrency;
cmbCurrency.DataTextField = "Name";
cmbCurrency.DataValueField = "CurrencyId";
cmbCurrency.DataBind();
}
}
Try this code:
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