(ASP.NET) 验证控件在控件事件处理程序之前或之后验证答案

【问题标题】：(ASP.NET) validation control validates before or after control event handler(ASP.NET) 验证控件在控件事件处理程序之前或之后验证
【发布时间】：2019-06-25 12:58:38
【问题描述】：

我是 ASP.NET 的初学者，只是对验证控件的工作原理有一些疑问：假设我有一本教科书和一个自定义验证，例如：

<asp:TextBox ID="txtTest" runat="server" ValidationGroup="test" OnTextChanged="txtTest_TextChanged" />

<asp:CustomValidator ID="CustomValidator" runat="server" ClientValidationFunction="validatePhoneNumbers"  ErrorMessage="xxx" OnServerValidate="CustomValidator_ServerValidate">*</asp:CustomValidator>

还有一个将表单提交到服务器的按钮

 <asp:Button ID="Button" runat="server" OnClick="Button_Click" Text="Submit" />

假设我禁用了 javascript，所以没有客户端 javascript 验证。

Q1-每个验证控件都有public void Validate ();方法，是不是意味着Validate()方法先被调用，间接调用了CustomValidator_ServerValidate()方法？

Q2-MSDN 文档指出：

如果请求是回发，则调用控制事件处理程序。之后，调用所有验证器控件的 Validate 方法，该方法设置各个验证器控件和页面的 IsValid 属性。

这意味着首先调用 txtTest_TextChanged() 然后调用 CustomValidator_ServerValidate() ，那么检查 Page.IsValid 有什么意义：

protected void txtTest_TextChanged(Object sender, EventArgs e)
{
 if (!Page.IsValid) return;

 lblMessage.Text = "Txt changed!";
}

因为 IsValid 只能在调用控件事件处理程序后设置？

【问题讨论】：

标签： javascript asp.net .net validation page-lifecycle

【解决方案1】：

Page.Validate() 隐式调用Raise PostBackEvent 并引发页面上所有验证器的ServerValidate 事件。

使用以下代码查看页面事件流并使用验证器。

<%@ Page Language="C#" Trace="true" TraceMode="SortByTime" %>

<!DOCTYPE html>
<script runat="server">
    void Page_Load(object sender, EventArgs e)
    {
        Trace.Write("Page_Load call");
    }

    protected void txtTest_TextChanged(object sender, EventArgs e)
    {
        Trace.Write("txtTest_TextChanged call");
        //force validation manually to check Page.IsValid
        Page.Validate(); //comment to cause runtime error in the next row
        Trace.Write("Page is valid", Page.IsValid.ToString());

    }
    //Server side validation. Never trust user input and client side validation
    protected void CustomValidator_ServerValidate(object source, ServerValidateEventArgs args)
    {
        Trace.Write("CustomValidator_ServerValidate call");
        if (args.Value == "123")
            args.IsValid = false;
    }

    protected void Button_Click(object sender, EventArgs e)
    {
        //if (Page.IsValid)
        //{
        //    Trace.Write("Button_Click call. Page.IsValid");
        //}
        Trace.Write("Button_Click call");
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Page event flow</title>
    <script>
        //client side validation. Never trust it.
        //It is for user convenience only
        function validatePhoneNumbers(sender, args) {
            console.log('validatePhoneNumbers',sender.ControlToValidate);
            if (args.Value == '1')
                args.IsValid = false;
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
        <div>
            <%-- Show client and server side validation errors --%>
            <asp:ValidationSummary runat="server" ID="vsSummary" />
            <%-- CausesValidation is false by default. No server validation before OnTextChanged --%>
            <asp:TextBox ID="txtTest" runat="server" 
                AutoPostBack="true" 
                OnTextChanged="txtTest_TextChanged" />
            <%-- ControlToValidate is optional for CustomValidator and mandatory for other validators --%>
            <asp:CustomValidator ID="CustomValidator" runat="server" 
                ClientValidationFunction="validatePhoneNumbers" ControlToValidate="txtTest"  
                ErrorMessage="xxx" OnServerValidate="CustomValidator_ServerValidate">*</asp:CustomValidator>
            <%-- CausesValidation is true by default. Server validation occurs before OnClick --%>
            <asp:Button ID="Button" runat="server" OnClick="Button_Click" Text="Submit" />
        </div>
    </form>
</body>
</html>

【讨论】：