C# 客户端验证在共享主机上不起作用，但在调试时起作用

我在模型类中具有以下属性：

[MaxLength(9), Required, DisplayName("Social security number")]
[RegularExpression(@"\d{3}-\d\d-\d{4}", ErrorMessage = "Invalid social security number")]
public string SocialSecurityNumber { get; set; }

标记（剃刀）：

生成的HTML代码是：

<input data-val="true" data-val-regex="Invalid social security number" data-val-regex-pattern="\d{3}-\d\d-\d{4}" data-val-required="The Social security number field is required." id="ssn" name="SocialSecurityNumber" type="text" value="">
<span class="field-validation-valid" data-valmsg-for="SocialSecurityNumber" data-valmsg-replace="true"></span>

我的本地电脑的html代码似乎有

class=“input validation error”

，而主机站点上不存在该代码

<input data-val="true" data-val-regex="Invalid social security number" data-val-regex-pattern="\d{3}-\d\d-\d{4}" data-val-required="The Social security number field is required." id="ssn" name="SocialSecurityNumber" type="text" value="">
<span class="field-validation-valid" data-valmsg-for="SocialSecurityNumber" data-valmsg-replace="true"></span>

<input data-val="true" data-val-regex="Invalid social security number" data-val-regex-pattern="\d{3}-\d\d-\d{4}" data-val-required="The Social security number field is required." id="ssn" name="SocialSecurityNumber" type="text" value="" class="input-validation-error">
<span class="field-validation-error" data-valmsg-for="SocialSecurityNumber" data-valmsg-replace="true"><span for="ssn" class="" style="">Invalid social security number</span></span>