如果需要字段验证的条件

Question

我在 c#.net 中有一个 DropDownList 和一个 TextBox。如果 DropDownList 值为 "No"，则必须在 TextBox 中输入一些值。如果下拉列表值为是，则该文本框不需要必填字段验证器。如何让它成为可能？

<asp:DropDownList ID="dropdownlist1" runat="server"
    CssClass="NormalText" Width="155px" AutoPostBack="true"
    onselectedindexchanged="ddls_SelectedIndexChanged">
    <asp:ListItem Selected="True" Value=""></asp:ListItem>    
    <asp:ListItem Value="Yes">Yes</asp:ListItem>
    <asp:ListItem Value="No">No</asp:ListItem>
</asp:DropDownList>
<br />
<br />
<asp:TextBox ID="Textbox1" runat="server" CausesValidation="True"></asp:TextBox>
&nbsp;
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"
    ControlToValidate="Textbox1" ErrorMessage="Explanation needed If you select NO">
</asp:RequiredFieldValidator>
</td>


protected void dropdownlist1_SelectedIndexChanged(object sender, EventArgs e)
{
}

Answer 1

使用此代码进行条件验证：

protected void dropdownlist1_SelectedIndexChanged(object sender, EventArgs e)
{
    if(dropdownlist1.SelectedValue == "No")
    {
       RequiredFieldValidator1.Enabled = true;
    }
    else if(dropdownlist1.SelectedValue == "Yes")
    {
       RequiredFieldValidator1.Enabled = false;
    }
}

可选，您可能还必须设置提交按钮验证组：

 ButtonSubmit.ValidationGroup = string.Empty;

未启用字段验证器时。

如果需要字段验证的条件

If condition for required field validation

c#

requiredfieldvalidator

drop-down-menu