如何从占位符获取所有文本框？ asp.net c＃网络表格

Question

I have a asp:placeholder on my html and I'm accessing to it to add textboxes and labels for questions and answers.

The "form" is created correctly I got all the labels with the questions and a textbox for each answer, however when I try after the button click runatserver the Placeholder1 is always empty.

I have tried a lof of things to get the textbox values to insert on a database without luck.

Below my code.

Thank you for your help in advance.

HTML code for the form inside a webform:

/* form for the buttons and title*/

<form id="form2" runat="server">

    <div align="center">
    </div>
    <div>
        <div align="center" class="form-group">
            <h4>
                <asp:label runat="server" id="title"></asp:label>
            </h4>
            <br />
            <br />
            <div align="center">
                place holder for the questions&answers

                    <asp:placeholder id="Placeholder1" runat="server">
                    </asp:placeholder>
            </div>
        </div>
    </div>
    <br />
    <br />

C# code to get how many questions and then add a textbox for each answer, using the cicle with a counter to add a id+counter

/* c# a counter is made to increment a number to the id*/

Adding controls to the PlaceHolder1     
/* add controls: */

add labels inside the counter for all number of rows of the sqlresult*/

Labels

Label quest= new Label();
quest.ID = "quest" + counter;
quest.Attributes.Remove("class");
quest.Attributes.Add("class", "exampleFormControlInput1");

quest.text = "sql query";

Textbox / add textbox on the cicle /

TextBox answer = new TextBox();
answer .ID = "answer " + counter;
answer .Attributes.Remove("class");
answer .Attributes.Add("class", "form-control");

PlaceHolder1.Controls.Add(quest);
PlaceHolder1.Controls.Add(new LiteralControl("<br>"));
PlaceHolder1.Controls.Add(answer);
PlaceHolder1.Controls.Add(new LiteralControl("<br>"));

Check how many controls are inside of the PlaceHolder1

Trying to check how many controls in the PlaceHolder1

count = PlaceHolder1.Controls.Count;

always 0

Answer 1

You probably are not recreating the Controls on PostBack. See this working example.

protected void Page_Load(object sender, EventArgs e)
{
    if (IsPostBack == false)
    {
        //do not create controls here
    }

    for (int count = 0; count < 5; count++)
    {
        TextBox answer = new TextBox();
        answer.ID = "answer " + count;
        PlaceHolder1.Controls.Add(answer);
    }
}

And then on PostBack

protected void Button1_Click(object sender, EventArgs e)
{
    int count = PlaceHolder1.Controls.Count;

    for (int i = 0; i < count; i++)
    {
        TextBox answer = PlaceHolder1.FindControl("answer " + i) as TextBox;
        Label1.Text += answer.Text + "<br>";
    }
}