Javascript 更改 asp :textbox visible property to true

Question

我正在尝试创建一个表单，其中应根据下拉列表显示或隐藏文本框，如果仅显示文本框，还要验证文本框。

有人可以帮我吗？

<asp:DropDownList 
    ID="txt_days" 
    CssClass="txt_drpbx" 
    runat="server"  
    siz="10" 
>
    <asp:ListItem Text="Select" Value="0"></asp:ListItem>
    <asp:ListItem Text="1" Value="1"></asp:ListItem>
    <asp:ListItem Text="2" Value="2"></asp:ListItem>
</asp:DropDownList>
<asp:RequiredFieldValidator 
    ID="RequiredFieldValidator6" 
    runat="server" 
    ControlToValidate="txt_days" 
    ForeColor="Red" 
    ErrorMessage="Please Select No of days on leave" 
    InitialValue="0" 
    ValidationGroup="fdbk_chk"
>*</asp:RequiredFieldValidator>
<asp:TextBox 
    ID="txt_todate" 
    runat="server" 
    ReadOnly="true" 
    Visible="false" 
    CssClass="txt_bx"
></asp:TextBox>
<asp:RequiredFieldValidator 
    ID="RequiredFieldValidator1" 
    runat="server" 
    ControlToValidate="txt_todate" 
    ForeColor="Red" 
    ErrorMessage="Please Select Feedback Given For" 
    ValidationGroup="fdbk_chk"
>*</asp:RequiredFieldValidator>
<asp:Button 
    ID="btn_submit" 
    Text="Submit" 
    CssClass="btn_button" 
    runat="server" 
    onclick="btn_submit_Click" 
    ValidationGroup="fdbk_chk" 
/>
<asp:ValidationSummary 
    ID="ValidationSummary1" 
    runat="server" 
    HeaderText="Some fields are missing" 
    ShowMessageBox="True" 
    ShowSummary="False" 
    ValidationGroup="fdbk_chk" 
/>

Answer 1

试试这个:

<script>

    function ShowHideTextBox(ddlId)
    {
         var ddl = document.getElementById(ddlId.id);

         if(ddl.value == 1)  //your condition
         {
             document.getElementById('txt_todate').style.display = 'none';
          }
         else
         {
             document.getElementById('txt_todate').style.display = '';

         }
    } 

<asp:DropDownList ID="txt_days" CssClass="txt_drpbx" runat="server"  siz="10" onchange="ShowHideTextBox(this);" 

<asp:TextBox ID="txt_todate" runat="server" ReadOnly="true" Visible="false" CssClass="txt_bx"></asp:TextBox>