Add/remove user controls programaticaly to placeholder

Jordan Trajkov

I make one asp.net web forms app, I create user control, in this user control I insert few standard .net controls. Now in my page.aspx I want dynamicly to insert this user control. I put a button, something like "Add new control".
If I click on it I'm adding a new control to the page. And all this works fine.

I have a problem in removing of this controls. I write a function for removing. But first time when I click it doesn't remove the control, I have to click another time to remove the last control. I think is something with postback, don't know why at first post back it doesn't remove the control.

I'm addding programaticly controls to PlaceHolder which is inside UpdaPanel. Here is the c# code how i do this, pls anybody knows where i make mistake?

public partial class Clasess_And_Events : System.Web.UI.Page
{
protected int NumberControlsForCategory
{
get { return (int)ViewState["NumControlsForCategory"]; }
set { ViewState["NumControlsForCategory"] = value; }
}
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
//Initiate the counter of dynamically added controls
this.NumberControlsForCategory = 0;
}
else
{
//Controls must be repeatedly be created on postback
this.createControlsCategory();
}
}
private void createControlsCategory()
{
int count = this.NumberControlsForCategory;
for (int i = 0; i < count; i++)
{
Control myUserControl = (Control)Page.LoadControl("UserControls/CategoryDropdown.ascx");
myUserControl.ID = "CategoryControl_ID_" + i.ToString();
PlaceHolder1.Controls.Add(myUserControl);
}
}
protected void Add_Controll_Click(object sender, EventArgs e)
{
Control myUserControl = (Control)Page.LoadControl("UserControls/CategoryDropdown.ascx");
myUserControl.ID = "CategoryControl_ID_" + NumberControlsForCategory.ToString();
PlaceHolder1.Controls.Add(myUserControl);
this.NumberControlsForCategory++;
LinkButton10.Visible = true;
}
protected void Remove_Control_Click(object sender, EventArgs e)
{
Control myUserControl = (Control)Page.FindControl("CategoryControl_ID_" + NumberControlsForCategory.ToString());
PlaceHolder1.Controls.Remove(myUserControl);
this.NumberControlsForCategory--;
}
}

5 Replies

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Midhun Tp10y ago
Accepted answer
Hi, I think the else condition in the postback is your problem. You should try commenting out that else condition and check it. It should work fine then. I couldn't understand what is the need of crrating controls on every postback. You are already creating them using add button click. Just comment out else condition and check if remove button click is working fine.
0
Midhun Tp10y ago
Ok. You are correct. So we can do small change in below code only -
protected void Remove_Control_Click(object sender, EventArgs e)
{
Control myUserControl = (Control)Page.FindControl("CategoryControl_ID_" + (NumberControlsForCategory-1).ToString());
PlaceHolder1.Controls.Remove(myUserControl);
this.NumberControlsForCategory--;
}
Rest of your code will remains the same as your question. Now check it.
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Jordan Trajkov10y ago
Yes u r right. but now i'm losing the content inisde the controls. They are all refreshed and if i have textboxes with some text they are all empty. I mean if i insert new textbox and insert some text, then add new textbox, the texbox number 1 now is empty.
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Midhun Tp10y ago
Hi, you should manage that for loop inside the add button click function.
0
Jordan Trajkov10y ago
I'mcrrating controls on every postback because if i dont, with button click i will create only one control everytime, i mean the control which i create with a previous button click on post back is removed.
0