如何获得 MVC3 模型验证的真假输出

Question

我正在使用表单发布信息，并且我的模型已内置验证。我知道我可以使用以下任一方法来验证字段：

@Html.ValidationSummary() //To validate all fields

@Html.ValidationMessageFor(x => x.FirstName) //To validate single field

这两种方法都只返回一个 HTML 列表（For ValidationSummary）或一个跨度（ValidateionMessageFor）。

我想要做的只是得到一个正确或错误的声明，如果该字段有效或无效（如果没有，则为 null），以便我可以对包含输入的框甚至标签进行一些自定义样式为它。

有谁知道是否有这样的代码可以做到这一点，比如@Html.IsValid(x => x.FirstName)

这是我的模型和视图。该模型正在通过并正确验证，这只是我是否可以获得布尔值而不是 HTML 字符串的问题。

型号：

using System.ComponentModel.DataAnnotations;

namespace X.Web.Helpers
{
    public class RequestSamplesModel
    {
        [Required]
        public string FirstName { get; set; }
        [Required]
        public string LastName { get; set; }

        public string Email { get; set; }
        [Required]
        public string Line1 { get; set; }
        [Required]
        public string Line2 { get; set; }
        [Required]
        public string City { get; set; }
        [Required]
        public string Postcode { get; set; }
        [Required]
        public string Country { get; set; }
    }
}

查看：

@{
    Layout = "~/Views/Shared/_PlainLayout.cshtml";
}
@using X.Web.Helpers
@model RequestSamplesModel

<form action="/Site/RequestSamples" method="POST">
    <div class="form-item">
        <span>First Name:</span>@Html.TextBoxFor(x => x.FirstName)</div>
    <div class="form-item">
        <span>Last Name:</span>@Html.TextBoxFor(x => x.LastName)</div>
    <div class="form-item">
        <span>Email:</span>@Html.TextBoxFor(x => x.Email)</div>
    <div class="form-item">
        <span>Address 1:</span>@Html.TextBoxFor(x => x.Line1)</div>
    <div class="form-item">
        <span>Address 2:</span>@Html.TextBoxFor(x => x.Line2)</div>
    <div class="form-item">
        <span>City:</span>@Html.TextBoxFor(x => x.City)</div>
    <div class="form-item">
        <span>Postcode:</span>@Html.TextBoxFor(x => x.Postcode)</div>
    <div class="form-item">
        <span>Country:</span>@Html.TextBoxFor(x => x.Country)</div>
    <div class="form-item">
        <input class="submit-button" type="image" src="/_content/images/email-submit.gif" /></div>
</form>

Answer 1

有谁知道是否有这样的代码可以做到这一点，比如 @Html.IsValid(x => x.FirstName)

不，没有内置这样的代码。但是写一个这样就很简单了：

public static class HtmlExtensions
{
    public static bool IsValid<TModel, TProperty>(
        this HtmlHelper<TModel> htmlHelper, 
        Expression<Func<TModel, TProperty>> expression
    )
    {
        var modelState = htmlHelper.ViewData.ModelState;
        var name = ExpressionHelper.GetExpressionText(expression);
        var key = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name);
        ModelState value;
        return !modelState.TryGetValue(key, out value) || 
               value.Errors.Count == 0;
    }
}

现在在您看来，只需将扩展方法纳入范围，然后：

@if (Html.IsValid(x => x.FirstName))
{
    @:<div>Super, the first name is valid</div>
}