关于ValidatorEnable的工作机制

ASP.NET提供多个验证控件进行客户端验证.每个控件都触发相应的客户端的JavaScript进行数据验证。在ASP.NET的早期版本中，客户端Javascript库是公开进行修改。从ASP.NET 2.0开始，验证控件所使用的脚本库WebUIValidation.js成为一种System.Web程序集内嵌入资源。本文着眼于了解他们的工作机制和在页面的验证过程。 

验证控件的工作机制

为了演示asp.net验证过程,我们新建一个名叫SimpleValidationTest的简单web application.
1.用VS新建一个website:SimpleValidationTest
2. 

<form id="form1" runat="server">
<div>
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <asp:RequiredFieldValidator
        ID="RequiredFieldValidator1" runat="server" ErrorMessage="RequiredFieldValidator"
         ControlToValidate="TextBox1">
        </asp:RequiredFieldValidator>
    <asp:Button ID="Button1" runat="server" Text="Button" />
    <asp:ValidationSummary ID="ValidationSummary1"  runat="server" />
</div>
</form>

当asp.net服务器端验证控件被使用时,在页面最终输出javascript代码来实现验证.asp.net所有的验证控件都继承自BaseValidator.在该类中注册通用的javascript脚本,输出通用的html.

当页面加入了asp.net验证控件.form将发生改变:

onsubmit="javascript:return WebForm_OnSubmit();"

在OnPreRender方法里,调用RegisterValidatorCommonScript来注册验证控件通用的javascript脚本,最终通过RegisterValidatorCommonScript函数来实现.

在render阶段,通过Page.ClientScript.RegisterOnSubmitStatement方法把onsubmit添加到form 上的.

function WebForm_OnSubmit() {
   if (typeof(ValidatorOnSubmit) == "function" && ValidatorOnSubmit() == false)
      return false;

   return true;
}

WebForm_OnSubmit函数在form提交的时候被调用.如果页面无效,页面将无法提交.该条件由alidatorOnSubmit函数决定.

var Page_ValidationActive = false;
if (typeof(ValidatorOnLoad) == "function") {
    ValidatorOnLoad();
}

function ValidatorOnSubmit() {
    if (Page_ValidationActive) {
        return ValidatorCommonOnSubmit();
    }
    else {
        return true;
    }
}

ValidatorOnLoad函数遍历validators数组,并初始化每项,设置Page_ValidationActive为true.当ValidatorOnSubmit被调用时,由于Page_ValidationActive为true,ValidatorCommonOnSubmit被调用.

function ValidatorCommonOnSubmit() {
    Page_InvalidControlToBeFocused = null;
    var result = !Page_BlockSubmit;
    if ((typeof(window.event) != "undefined") && (window.event != null)) {
        window.event.returnValue = result;
    }
    Page_BlockSubmit = false;
    return result;
}

缺省Page_BlockSubmit被设置为false.在页面客户端验证期间Page_BlockSubmit被设置为!Page_IsValid. 

深入理解页面验证 

<script type="text/javascript">
<!--
var Page_ValidationSummaries =  new Array(document.getElementById("ValidationSummary1"));
var Page_Validators =  new Array(document.getElementById("RequiredFieldValidator1"));
// -->
</script>

上面的代码显示ValidationSummary1控件对象被加入到Page_ValidationSummaries数组,RequiredFieldValidator1控件对象被加入到Page_Validators数组中.

Validator控件主要有controltovalidate, errormessage, evaluationfunction 和 initialvalue.controltovalidate的值对应要验证的控件ID.errormessage值是错误消息提示.initialvalue为初始值.evaluationfunction由服务器端验证控件的类型决定.

Validator type	evaluationfunction
Required Field Validator	RequiredFieldValidatorEvaluateIsValid
Range Validator	RangeValidatorEvaluateIsValid
Custom Validator	CustomValidatorEvaluateIsValid
Compare Validator	CompareValidatorEvaluateIsValid

此前，我们提到到Page_IsValid决定页面是否有效。但是,那些函数设置该值以及这些函数如何被调用的？
使用我们上面的例子来显示这个过程. 我们监测button控件呈现HTML的过程.缺省情况下,每个按钮控件都会加上下面属性.

onclick="javascript:WebForm_DoPostBackWithOptions(new
   WebForm_PostBackOptions("Button1", "", true, "", "", false, false))"

上面的onclick属性由按钮的AddAttributesToRender方法添加.函数WebForm_DoPostBackWithOptions和WebForm_PostBackOptions在WebForms.js中.WebForm_DoPostBackWithOptions使用WebForm_PostBackOptions对象作为参数,调用Page_ClientValidate函数.Page_ClientValidate函数负责设置Page_IsValid变量的值.

下面显示Button控件点击完整的处理过程.

    1.  按钮被点击
    2.  函数WebForm_DoPostBackWithOptions被调用 

function WebForm_DoPostBackWithOptions(options) {
    var validationResult = true;
    if (options.validation) {
        if (typeof(Page_ClientValidate) == 'function') {
            validationResult = Page_ClientValidate(options.validationGroup);
        }
    }
    if (validationResult) {
        if ((typeof(options.actionUrl) != "undefined") &&
                           (options.actionUrl != null) &&
                           (options.actionUrl.length > 0))
        {
            theForm.action = options.actionUrl;
        }
        if (options.trackFocus) {
            var lastFocus = theForm.elements["__LASTFOCUS"];
            if ((typeof(lastFocus) != "undefined") && (lastFocus != null)) {
                if (typeof(document.activeElement) == "undefined") {
                    lastFocus.value = options.eventTarget;
                }
                else {
                    var active = document.activeElement;
                    if ((typeof(active) != "undefined") && (active != null)) {
                        if ((typeof(active.id) != "undefined") &&
                                           (active.id != null) &&
                                           (active.id.length > 0))
                        {
                            lastFocus.value = active.id;
                        }
                        else if (typeof(active.name) != "undefined") {
                            lastFocus.value = active.name;
                        }
                    }
                }
            }
        }
    }
    if (options.clientSubmit) {
        __doPostBack(options.eventTarget, options.eventArgument);
    }
}

    3. 函数Page_ClientValidate被调用

function Page_ClientValidate(validationGroup) {
    Page_InvalidControlToBeFocused = null;
    if (typeof(Page_Validators) == "undefined") {
        return true;
    }
    var i;
    for (i = 0; i < Page_Validators.length; i++) {
        ValidatorValidate(Page_Validators[i], validationGroup, null);
    }
    ValidatorUpdateIsValid();
    ValidationSummaryOnSubmit(validationGroup);
    Page_BlockSubmit = !Page_IsValid;
    return Page_IsValid;
}

    4. Page_IsValid 被设置.
    5. form 被提交
    6. onSubmit 事件被触发
    7. 返回WebForm_OnSubmit
    8. 返回 ValidatorOnSubmit
    9. 返回 ValidatorCommonOnSubmit
    10. 返回 !Page_BlockSubmit
    11. 返回 !(!Page_IsValid)

如果页面是有效的,将提交页面.如果页面无效,就不能提交页面,同时页面的validation summary 控件显示错误消息.函数ValidatorUpdateIsValid 和 ValidationSummaryOnSubmit负责这方面的功能. 

自定义验证控件 

在前面内容中，我们看到页面的验证过程内部机制。在下面的例子，我们将展示根据条件关闭或打开验证。在我们上面的示例程序中添加另一个文本框和自定义验证。验证函数决定验证的启用与否。该validateTextBox1函数接受两个参数，src和args。当在TextBox2中输入的值时,args.Value为true.RequiredFieldValidator1以编程方式被禁用。这是通过利用内置的ValidatorEnable功能来实现的.它需要这两个参数:验证器的名称和一个布尔型标志启用/禁用。自定义验证器的errormessage属性使用代码动态改变.根据用户输入,如果args.IsValid为false则页面无法提交。 

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Understanding .NET Validation</title>
<script type="text/javascript">
function validateTextBox1(src, args)
{
    if (args.Value == "true")
    {
        ValidatorEnable(RequiredFieldValidator1, false);
        src.errormessage = "TextBox1 required field validator is disabled";
    }
    else
    {
        ValidatorEnable(RequiredFieldValidator1, true);
        src.errormessage = "Enter true, not '"+args.Value+"' to disable TextBox1 required field validator";
    }
     args.IsValid = false;
}
</script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    TextBox 1: <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"
          Text="*" ControlToValidate="TextBox1"
          Display="Dynamic"
          ErrorMessage="TextBox1 is required"></asp:RequiredFieldValidator>
       <br />
       Disable required field for TextBox1?
    <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
    <asp:CustomValidator ID="CustomValidator1" runat="server"
          Text="*" ControlToValidate="TextBox2" Display="Dynamic"
          ErrorMessage="CustomValidator"
          ClientValidationFunction="validateTextBox1"
          ValidateEmptyText="True"></asp:CustomValidator>
    <asp:ValidationSummary ID="ValidationSummary1" runat="server" />
    <asp:Button ID="Button1" runat="server" Text="Button"  />
    </div>
    </form>
</body>
</html>