user control inside placeholder

[Guest]

Hello,
I am trying to insert multiple instances of a custom user control into a
placeholder on an aspx page, based on the records retrieved from the
database. I use the datareader to loop through the records and I want to
create a new instance of the user control for each record and then change the
properties of the controls within each user control. The problem is that
after I create the new instance of the user control, I get a protected
property error when I try to change the properties of a control within that
instance of the user control. I tried changing the class definition so that
the controls on the user control were declared as public, but that does not
seem to solve the problem. I get a Event.Arg error now. Any suggestions
would be greatly appreciated.

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Data.Odbc;

namespace MyNamespace
{
/// <summary>
/// Summary description for MyWebPage.
/// </summary>
public class MyWebPage : System.Web.UI.Page
{
protected System.Web.UI.WebControls.PlaceHolder MyPlaceHolder;

private void Page_Load(object sender, System.EventArgs e)
{
string strSql="SELECT * FROM MyDatabaseTable";

try
{ //Connection string for MyODBC 3.51
string MyConString = "DRIVER={MySQL ODBC 3.51 Driver};" +
"SERVER=localhost;" +
"DATABASE=MyDatabase;" +
"UID=root;" +
"PASSWORD=MyPassword;" +
"OPTION=3";
//Connect to MySQL using MyODBC
OdbcConnection MyConnection = new OdbcConnection(MyConString);
MyConnection.Open();
OdbcCommand MyCommand = new OdbcCommand(strSql,MyConnection);


OdbcDataReader MyDataReader;
MyDataReader = MyCommand.ExecuteReader();

while (MyDataReader.Read())
{
MyUserControl MyUserControl1 = new MyUserControl();

MyUserControl1.Label1.Text="Hello World"; //ERROR ON THIS LINE!!

MyPlaceHolder.Controls.Add(MyUserControl1);
}
//Close all resources
MyDataReader.Close();
MyConnection.Close();
}
catch
{
string ErrorMessage = e.ToString();
string strErrorMessage=ErrorMessage;
}
}

 

[Ollie Riches]

you should create a property on your user control that stores the text for
the label and then override the databind method to bind the text to the
label control. This then allows you to create an instance of the controlm
assign the variable to the property and then call databind on the control
after it has been added to the place holder.

e.g.

public class myUserControl : System.Web.UI.UserControl
{
protected System.Web.UI.WebControls.Label lblName;

private string m_name;
public string Name
{
get
{
return m_name;
}
set
{
m_name = value;
}
}

private void Page_Load(object sender, System.EventArgs e)
{
DataBind();
}

public override void DataBind()
{
lblName.Text = m_name;
base.DataBind();
}


--
HTH

Ollie Riches
http://www.phoneanalyser.net

Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a programmer
helping programmers.

 

[Guest]

Thanks that almost works! I created a property on the user control , set the
value and then add the user control to the placeholder, but when I call the
databind method I get an error: Object reference not set to an instance of
an object. The error occurs in the databind method:

public override void DataBind()
{
lblName.Text = m_name; //Error on this line
base.DataBind();
}

The code looks like this now:

MyUserControl MyUserControl1 = new MyUserControl();

MyUserControl1.Name="Hello World";

MyPlaceHolder.Controls.Add(MyUserControl1);

MyUserControl1.DataBind(); //ERROR ON THIS LINE!!

 

[Ollie Riches]

where are you doing this? in the page load event


--
HTH

Ollie Riches
http://www.phoneanalyser.net

Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a programmer
helping programmers.

 

[Guest]

This is what the web form and the user control look like without all the ADO:

WEB FORM:

{
public class MyWebForm : System.Web.UI.Page
{
protected System.Web.UI.WebControls.PlaceHolder MyPlaceHolder;

private void Page_Load(object sender, System.EventArgs e)
{
MyWebUserControl MyWebUserControl1=new MyWebUserControl();
MyWebUserControl1.Name="Hello World";
MyPlaceHolder.Controls.Add(MyWebUserControl1); //Works fine through here
}

}


And the User Control looks like this:

public class MyUserControl : System.Web.UI.UserControl
{
protected System.Web.UI.WebControls.Label MyLabel;

private string m_name;
public string Name
{
get
{
return m_name;
}
set
{
m_name = value;
}
}

private void Page_Load(object sender, System.EventArgs e)
{
DataBind();
}

public override void DataBind()
{
MyLabel.Text = m_name; // ERROR ON THIS LINE Object reference not set to
an instance of an object.
// on mouseover, MyLabel=<undefined value>.
// m_name has the correct value.
base.DataBind();
}

}

 

[Ollie Riches]

all you need to do is a DataBind on the PlaceHolder when you have finished
adding the user controls. It will propagate the event to all its contained
child controls.

private void Page_Load(object sender, System.EventArgs e)
{
MyWebUserControl MyWebUserControl1=new MyWebUserControl();
MyWebUserControl1.Name="Hello World";
MyPlaceHolder.Controls.Add(MyWebUserControl1); //Works fine through here
MyPlaceHolder.DataBind();
}


--
HTH

Ollie Riches
http://www.phoneanalyser.net

Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a programmer
helping programmers.