I am having some trouble with my webpart connections on postbacks.
I basically have two webparts in the same zone, 1 provider and 1 consumer.
The provider has a dropdown list and submit button and the consumer has a
text box that displays data depending on what is selected in the provider.
On the initial page hit, The consumer connection is established before the
CreateChildCont rols event (which is fine), but on the postback, the
CreateChildCont rols event occurs before the consumer connection is
established, so the the CreateChildCont rols method does not know which value
was selected in the provider at this time.
Does anyone else have this problem or know the correct way to do this?
I've noticed that the CreateChildCont rols only gets fired before the
connection gets established when there are any input (text, checkbox, etc)
controls on the form. If you run the code below, you'll notice the consumer
is only rendered every other postback because when the connection isn't set,
the consumer can't render the control because it doesn't know which type to
display. And when the consumer has no input controls, on the next postback,
the connection is established first and the controls get rendered.
I've come up with a workaround, but I'd like a cleaner solution. My
workaround is to just call CreateChildCont rols again in the Consumer
connection code (You'll see it commented out in the code below). This will
ensure that the controls are created again after the connection has been
made. I don't like this because 1) On the initial page hit the controls we
be rendered and then deleted and re-rendered when the connection is made
which is inefficient.
I guess some other questions would be...
1. I know the CreateChildCont rols event is called at different times
depending on page circumstances, but does anyone know those circumstances?
2. Is there a way to make sure that the connection happens before the
CreateChildCont rols? Or a way to force the connection at some point in the
page life cycle?
Any help with this would be greatly appreciated... I've been banging my head
against this one for a couple days now.
Thanks!!!
Code follows...
<%@ Page Language="C#" AutoEventWireup ="true" CodeFile="Defau lt.aspx.cs"
Inherits="_Defa ult" EnableViewState ="false"%>
<%@ Register TagPrefix="aspS ample" Namespace="Samp les.AspNet.CS.C ontrols" %>
<script runat="server">
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>Untitl ed Page</title>
</head>
<body>
<form id="form1" runat="server">
<asp:WebPartMan ager ID="mgr" runat="server">
<StaticConnecti ons>
<asp:WebPartCon nection ID="conn1"
ConsumerConnect ionPointID="MyC onsumer"
ConsumerID="con sumer1"
ProviderConnect ionPointID="MyP rovider"
ProviderID="pro vider1" />
</StaticConnectio ns>
</asp:WebPartMana ger>
<asp:WebPartZon e ID="WebPartZone 1" runat="server">
<ZoneTemplate >
<aspSample:ZipC odeWebPart ID="provider1" runat="server" Title="My
Provider" />
<aspSample:Weat herWebPart ID="consumer1" runat="server" Title="My
Consumer" />
</ZoneTemplate>
</asp:WebPartZone >
<asp:Connection sZone ID="Connections Zone1" runat="server">
</asp:Connections Zone>
</form>
</body>
</html>
namespace Samples.AspNet. CS.Controls
{
using System;
using System.Web;
using System.Web.Secu rity;
using System.Security .Permissions;
using System.Web.UI;
using System.Web.UI.W ebControls;
using System.Web.UI.W ebControls.WebP arts;
public interface IMyConnection
{
string MySelection { get; }
}
public class ZipCodeWebPart : WebPart, IMyConnection
{
private string _mySelection = String.Empty;
private DropDownList _dll;
public ZipCodeWebPart( )
{
}
public virtual string MySelection
{
get { return _mySelection; }
}
[ConnectionProvi der("Zip Code Provider", "MyProvider ")]
public IMyConnection ProvideMyProvid er()
{
return this;
}
protected override void CreateChildCont rols()
{
Controls.Clear( );
_dll = new DropDownList();
_dll.Items.Add( "One");
_dll.Items.Add( "Two");
_dll.Items.Add( "Three");
_dll.CausesVali dation = true;
this.Controls.A dd(_dll);
Button myButton = new Button();
myButton.Text = "Display";
myButton.Click +=new EventHandler(my Button_Click);
this.Controls.A dd(myButton);
}
void myButton_Click( object sender, EventArgs e)
{
_mySelection = _dll.SelectedVa lue;
}
}
public class WeatherWebPart : WebPart
{
private IMyConnection _provider;
[ConnectionConsu mer("Zip Code Consumer", "MyConsumer ")]
public void GetMyProvider(I MyConnection Provider)
{
_provider = Provider;
}
protected override void OnPreRender(Eve ntArgs e)
{
EnsureChildCont rols();
}
protected override void CreateChildCont rols()
{
if (this._provider != null)
{
Controls.Clear( );
TextBox tb = new TextBox();
tb.ID = "myTextBox" ;
this.Controls.A dd(tb);
switch (_provider.MySe lection)
{
case "One":
tb.Text = "Display One Data";
break;
case "Two":
tb.Text = "Display Two Data";
break;
case "Three":
tb.Text = "Display Three Data";
break;
}
}
}
}
}
