Question

我有一个下拉列表，我在代码中动态开发。

  Dim objPreferenceDropdownList As DropDownList = New DropDownList()
                        objPreferenceDropdownList.ID = "objPreferenceDropdownList"
                        objPreferenceDropdownList.AppendDataBoundItems = "True"

              objPreferenceDropdownList.AutoPostBack = True

我使用不同的项目填充此下拉列表，例如

objPreferenceDropdownList.Items.Add(new ListItem("--Select Color--","0"));

 objPreferenceDropdownList.Items.Add(new ListItem("Red","1"));

 objPreferenceDropdownList.Items.Add(new ListItem("Blue","2"));

objPreferenceDropdownList.Items.Add(new ListItem("White", "3"));

objPreferenceDropdownList.Items.Add(new ListItem("Pink", "4"));

现在我需要验证下拉列表，它没有在下拉列表中选择任何项目，因为我动态创建了一个必需的字段验证器：

Dim reqPrefGroupValidator As RequiredFieldValidator = New RequiredFieldValidator()
                                reqPrefGroupValidator.ControlToValidate = "objPreferenceDropdownList"
                                reqPrefGroupValidator.InitialValue = "0"
                                reqPrefGroupValidator.SetFocusOnError = True
                                prefdiv.Controls.Add(reqPrefGroupValidator)

问题是必填字段验证器仅在dropdownlist为空时才有效，如果我需要在下拉列表的选定项目值为零时触发requiredfieldvalidator。

Answer 1

将验证器的InitialValue设置为0，验证器必须具有ID和ofcourse：

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" 
        ErrorMessage="RequiredFieldValidator" ControlToValidate="objPreferenceDropdownList" 
        InitialValue="0"></asp:RequiredFieldValidator>

Answer 2

您可以使用Compare Field Validator和CompareValue为0和CompareType int。

你可以这样做。

<asp:DropDownList runat="server" ID="objPreferenceDropdownList"></asp:DropDownList>
    <asp:CompareValidator ID="CompareValidator1" runat="server" ErrorMessage="plz Select Value" ValueToCompare="0" Operator="GreaterThan" ControlToValidate="objPreferenceDropdownList" Type="Integer"></asp:CompareValidator>
    <asp:Button ID="btnSubmit" runat="server" Text="Submit Form" OnClick="btnSubmit_Click" />

下拉列表的RequiredFieldValidator

2 个答案: