如何在asp.net中单击按钮时动态添加控件？

Question

I'm trying to add controls dynamically

Code:

AddVisaControl.ascx

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="AddVisaControl.ascx.cs" EnableViewState="false" Inherits="Pyramid.AddVisaControl" %>
<%@ Register assembly="BasicFrame.WebControls.BasicDatePicker" namespace="BasicFrame.WebControls" tagprefix="BDP" %>
<div id="divreg" runat="server">
<table id="tbl" runat="server">
<tr>
  <td class="style8"> Visa Number:</td>
  <td class="style20"><asp:TextBox ID="txtUser" Width="160px" runat="server"/></td>
  <td class="style22"> Country Name:</td>
  <td class="style23">
<asp:DropDownList ID="dropCountry" Width="165px" runat="server">
</asp:DropDownList></td>
</tr>
 <tr>
 <td class="style22"> Type of Visa:</td>
 <td class="style23">
<asp:DropDownList ID="dropVisa" Width="165px" runat="server"> </asp:DropDownList></td>
<td class="style22"> Type of Entry:</td>
<td class="style23">
<asp:DropDownList ID="dropEntry" Width="165px" runat="server"> </asp:DropDownList></td>
</tr>
<tr>
<td class="style8">&nbsp; Expiry Date</td>
<td class="style20">
</td>
</tr>
</table>

.cs code:

Below code is the problem when the first time I click add button it is adding controls properly but If I close the browser window and comes again and click the add button I got more controls

   static int i = 0;
    protected void addnewtext_Click(object sender, EventArgs e)
    {
        i++;
        for (int j = 0; j <= i; j++)
        {
            AddVisaControl ac = (AddVisaControl)Page.LoadControl("AddVisaControl.ascx");
            PlaceHolder1.Controls.Add(ac);
            PlaceHolder1.Controls.Add(new LiteralControl("<BR>"));
        }
    }

In the below image If I click add more visa button I want to get another visa details

Any ideas? Thanks in advance

Answer 1

I will show one examples you can try it your own way

An idea would be to create a list of buttons in which you'd store the buttons you created in btnCreateDynamic_click

you could have a method like:

private Button CreateButton(string id, string name)
        {
            Button b = new Button();
            b.Text = name;
            b.ID = id;
            b.Click += new EventHandler(Button_Click);
            b.OnClientClick = "ButtonClick('" + b.ClientID + "')";
            return b;
        }

in btnCreateDynamic_click you could have something like:

Button b = CreateButton("dinamicBtn"+myDinamicButtonsList.Count.ToString(),"dinamicBtn"+myDinamicButtonsList.Count.ToString());
myDinamicButtonsList.add(b);
and in the pageLoad for example you could do something like

foreach(button btn in myDinamicButtonsList){
    form1.Controls.Add(btn));
}

List<Button> myDinamicButtonsList = new List<Button>();

myDinamicButtonsList should be stored somewhere from where it could be retrieved after each request.

EDIT: In page load you could have something like this:

if(Session["myDinamicButtons"] == null){
    List<Button> myDinamicButtonsList = new List<Button>();
    Session["myDinamicButtons"] = myDinamicButtonsList;
}

foreach(Button btn in Session["myDinamicButtons"] as List<Button>){
    form1.Controls.Add(btn));
}

i didn't tested it but it should work.

also put on some information following may more help..

Your button click event at the client will cause a page postback that will start the ASP.Net Page Life-cycle.

Your button click event on the server is a PostBackEvent and you should be able to use the same method call CreateMyButton() that you used in the Load or Init events.

Answer 2

if you remove the static 'i' variable and use a hidenInput to maintain the no of created controls (or a session value) you will be fine.

But I suggest you read the following article to find a better way of creating dynamic controls :

Dynamic control creation in ASP.NET

Answer 3

Remove static int i = 0;

Change the method as below

  protected void addnewtext_Click(object sender, EventArgs e)
    {     

            AddVisaControl ac = (AddVisaControl)Page.LoadControl("AddVisaControl.ascx");
            PlaceHolder1.Controls.Add(ac);
            PlaceHolder1.Controls.Add(new LiteralControl("<BR>"));

    }