单击按钮时动态添加新文本框

Question

我正在使用此代码

<asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
<asp:Button ID="addnewtext" runat="server" Text="Add" onclick="addnewtext_Click" width="76px" />

和aspx.cs页面代码：

TextBox tb;
static int i = 0;
protected void addnewtext_Click(object sender, EventArgs e)
{
    tb = new TextBox();
    tb.ID = i.ToString();

    PlaceHolder1.Controls.Add(tb);
    i++;
}

每按一下按钮，我想添加另一个文本框。

Answer 1

原因：再次单击按钮时，它会回发到服务器端，并删除以前添加的动态文本框

解决方案：要再次添加它，您需要这样做

 TextBox tb;
static int i = 0;
protected void addnewtext_Click(object sender, EventArgs e)
{
        i++;
    for(j=0;j<=i;j++)
    {
    tb = new TextBox();
    tb.ID = j.ToString();

    PlaceHolder1.Controls.Add(tb);
    }

}

这意味着您需要再次创建添加的文本框...因为您正在动态地向页面添加控件...

这样的文章可能对您有所帮助： 在ASP.NET应用程序中保留动态创建控件的状态

Answer 2

让我们看一下列表视图

<asp:ListView ID="lvDynamicTextboxes" runat="server" 
  ItemPlaceholderID="itemPlaceholder">   <LayoutTemplate>     <table>       <asp:PlaceHolder ID="itemPlaceholder" 
        runat="server"></asp:PlaceHolder>     </table>   </LayoutTemplate>   <ItemTemplate>     <tr>       <asp:TextBox ID="txtText" runat="server">       </asp:TextBox>     </tr>   </ItemTemplate>      
</asp:ListView>

<asp:Button ID="btnAddTextBox" runat="server" 
  Text="Add" onclick="btnAddTextBox_Click" />

还有一些代码

private void BindListView()
{
    //get the current textbox count     int count = 1;
    if (ViewState["textboxCount"] != null)
        count = (int)ViewState["textboxCount"];

    //create an enumerable range based on the current count     IEnumerable<int> enumerable = Enumerable.Range(1, count);

    //bind the listview     this.lvDynamicTextboxes.DataSource = enumerable;
    this.lvDynamicTextboxes.DataBind();
}

private void IncrementTextboxCount()
{
    int count = 1;
    if (ViewState["textboxCount"] != null)
        count = (int)ViewState["textboxCount"];

    count++;
    ViewState["textboxCount"] = count;
}

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
   {
        this.BindListView();  
    }
}

protected void btnAddTextBox_Click(object sender, EventArgs e)
{
    this.IncrementTextboxCount();
    this.BindListView();
}

现在要从这些添加的文本框中提取值 ：

private IList<string> GetValues()
{
    List<string> values = new List<string>();
    TextBox txt = null;
    foreach (ListViewItem item in this.lvDynamicTextboxes.Items)
    {
        if (item is ListViewDataItem)
       {
            txt = (TextBox)item.FindControl("txtText");
            values.Add(txt.Text);
        }
    }
    return values;
}