http://aspdotnetcodebook.blogspot.com/2008/03/how-to-create-textbox-control.html
In Technique when creating
control dynamically in a Page Load event handler these controls will retain
their ViewState after the PostBack, but what if controls created dynamically at
runtime in a Button Click event handler instead of Page Load event then on PostBack
these controls ViewState are lost.To persists the ViewState of these child
controls we will recreate these controls again on a PostBack in overrideable
CreateChildControls() Method which is
called whenever
ASP.NET needs to create these
WebControl in a Control Tree.
// Add TextBoxes Control to Placeholder
private void CreateTextBoxes()
{
for (int counter = 0; counter <=
NumberOfControls; counter++)
{
TextBox tb = new TextBox();
tb.Width = 150;
tb.Height = 18;
tb.TextMode =
TextBoxMode.SingleLine;
tb.ID = "TextBoxID" +
(counter + 1).ToString();
// add some dummy data to
textboxes
tb.Text = "Enter Title
" + counter;
phTextBoxes.Controls.Add(tb);
phTextBoxes.Controls.Add(new
LiteralControl("<br/>"));
}
}
In CreateTextBoxes method I loop through ‘n’ numbers of
controls that we wants to create dynamically in phTextBoxes placeholder.
// Create TextBoxes on PostBack.
protected override void CreateChildControls()
{
// Here we are recreating controls
to persist the ViewState on every post back
if (Page.IsPostBack)
{
NumberOfControls += 1;
CreateTextBoxes();
}
else
{
CreateTextBoxes();
// Increase the control value
to 1
NumberOfControls = 0;
}
}
CreateChildControls method, here we are recreating control
on every
PostBack. If the page is created the first time we just
create these
controls and save 1 in the ViewState so we know that we have
created
these controls and assigned the controls id to 1.
// Increase the counter when button is clicked and add to
view
state
protected void btnAddTitle_Click(object sender, EventArgs e)
{
NumberOfControls += 1;
}
In button event handler we just increase the counter by 1,
and save its value to ViewState
for later retrieval.Once we have created these controls on ASP.NET page,
retrieving
data from these dynamically created controls is easy by using FindControl
method.
// Read TextBoxes Data
public int NumberOfControls
{
get
{
if (ViewState["Count"]
== null)
{
return 0;
}
return (int)ViewState["Count"];
}
set
{
ViewState["Count"] =
value++;
}
}
private void ReadTextBoxes()
{
strValue = string.Empty;
int n = NumberOfControls;
for (int i = 0; i <=
NumberOfControls; i++)
{
string boxName = "TextBoxID"
+ (i + 1).ToString();
TextBox tb =
phTextBoxes.FindControl(boxName) as TextBox;
strValue += tb.Text + "\n";
}
Response.Write(strValue);
}