如何将 RequiredFieldValidator 添加到 DropDownList 控件? [英] How to add a RequiredFieldValidator to DropDownList control?

问题描述

我有一个 DropDownList 绑定了一个 SqlDataSource 来显示数据库中的值.

I have a DropDownList binded with aSqlDataSource to display the values from the database.

我无法使用 RequiredFieldValidator 进行验证.

I am unable to validate using a RequiredFieldValidator.

推荐答案

在大多数情况下，您将其视为验证任何其他类型的控件，但使用所需字段验证器的 InitialValue 属性.

For the most part you treat it as if you are validating any other kind of control but use the InitialValue property of the required field validator.

<asp:RequiredFieldValidator ID="rfv1" runat="server" ControlToValidate="your-dropdownlist" InitialValue="Please select" ErrorMessage="Please select something" />

基本上它的意思是，如果在下拉列表中选择了除 InitialValue 中设置的 1 之外的任何其他值，则验证将成功.

Basically what it's saying is that validation will succeed if any other value than the 1 set in InitialValue is selected in the dropdownlist.

如果数据绑定，您需要在之后插入请选择"值，如下所示

If databinding you will need to insert the "Please select" value afterwards as follows

this.ddl1.Items.Insert(0, "Please select");

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