使用现有 HtmlHelper 和表达式的自定义 MVC HtmlHelper

Question

我正在尝试制作一个自定义 HtmlHelper，它将在现有 HtmlHelper 的帮助下生成多个 HTML 元素，例如 Html.TextBoxFor 和 Html.LabelFor。我遇到的主要问题是我无法创建这些现有助手使用的表达式，除非它们都单独传递到我的自定义 HtmlHelper 中。我希望能够将整个模型传递给自定义 HtmlHelper 并在帮助器内部创建表达式并将它们传递给现有的。我正在尝试这样做，希望这些属性仍然有效，例如 DisplayName 的必需和国际化。这可能吗？

我知道我可以通过表达式将每个 Address 属性传递给自定义 HtmlHelper 来做到这一点，但它不像在帮助程序中完成那样干净和易于使用。

地址模型

public class Address
{
    [Required(ErrorMessage = "Required"), DisplayName("First Name")]
    public String FirstName { get; set; }

    [Required(ErrorMessage = "Required"), DisplayName("Last Name")]
    public String LastName { get; set; }

    [Required(ErrorMessage = "Required"), DisplayName("Line 1")]
    public String Line1 { get; set; }

    [Required(ErrorMessage = "Required"), DisplayName("Line 2")]
    public String Line2 { get; set; }

    [Required(ErrorMessage = "Required"), DisplayName("City")]
    public String City { get; set; }

    [Required(ErrorMessage = "Required"), DisplayName("State")]
    public String State { get; set; }

    [Required(ErrorMessage = "Required"), DisplayName("Country")]
    public String Country { get; set; }

    [Required(ErrorMessage = "Required"), DisplayName("Postal Code")]
    public String PostalCode { get; set; }
}

自定义 HtmlHelper

public static class AddressExtension
{
    public static MvcHtmlString AddressEditorForModel<TModel>(this HtmlHelper<TModel> helper, Address address, String prefix, Boolean showLabels)
    {          
        // There will be more markup in here, this is just slimmed down..

        StringBuilder sb = new StringBuilder();
        sb.AppendLine(String.Format("<div id='{0}_AddressContainer' >", prefix));

        // First Name
        if (showLabels)
            sb.AppendLine(helper.DisplayFor(????).ToString());            
        sb.AppendLine(helper.EditorFor(????).ToString());

        // Last Name
        if (showLabels)
            sb.AppendLine(helper.DisplayFor(????).ToString());            
        sb.AppendLine(helper.EditorFor(????).ToString());

        // Line 1
        if (showLabels)
            sb.AppendLine(helper.DisplayFor(????).ToString());            
        sb.AppendLine(helper.EditorFor(????).ToString());

        // Line 2
        if (showLabels)
            sb.AppendLine(helper.DisplayFor(????).ToString());            
        sb.AppendLine(helper.EditorFor(????).ToString());

        // City
        if (showLabels)
            sb.AppendLine(helper.DisplayFor(????).ToString());            
        sb.AppendLine(helper.EditorFor(????).ToString());

        // State
        if (showLabels)
            sb.AppendLine(helper.DisplayFor(????).ToString());            
        sb.AppendLine(helper.EditorFor(????).ToString());

        // Country
        if (showLabels)
            sb.AppendLine(helper.DisplayFor(????).ToString());            
        sb.AppendLine(helper.EditorFor(????).ToString());

        // Postal Code
        if (showLabels)
            sb.AppendLine(helper.DisplayFor(????).ToString());            
        sb.AppendLine(helper.EditorFor(????).ToString());

        sb.AppendLine("</div>");

        return MvcHtmlString.Create(sb.ToString());
    }

查看（cshtml）

@Html.AddressEditorForModel(Model, "test", true)

Answer 1

您可以像这样使用反射和表达式树来做到这一点：

public static MvcHtmlString AddressEditorForModel<TModel>(this HtmlHelper<TModel> helper, string prefix, bool showLabels)
{          
    // There will be more markup in here, this is just slimmed down..

    StringBuilder sb = new StringBuilder();
    sb.AppendLine(String.Format("<div id='{0}_AddressContainer' >", prefix));

         //Create a parameter expression for the model type
         ParameterExpression paramExpr = Expression.Parameter(typeof (TModel));
         //Loop through the properties you want to create a DisplayFor for
         foreach (var property in typeof (TModel).GetProperties())
         {
             //Create a member access expression for accessing this property
             MemberExpression propertyAccess = Expression.MakeMemberAccess(paramExpr, property);
             //Create the lambda expression (eg. "x => x.Name")
             var lambdaExpr = Expression.Lambda<Func<TModel, string>>(propertyAccess, paramExpr);
             //Pass this lambda to the DisplayFor method
             sb.AppendLine(helper.DisplayFor(lambdaExpr).ToString());

         }

...rest of your method

但是，这假设 TModel 是您的 Address 对象，因此您也不需要传入它。HTML 中的 TModel helpers 来自强类型视图，所以如果你有一个 @model 类型为 Address 的视图，那么你可以使用上面的方法

视图会这样使用它：

@model Address

@Html.AddressEditorForModel("prefix", true)