DropDownList和EditorTemplates

Question

我有一个名为Invoice的实体，我正在为数据注释扩展它

   [MetadataType(typeof(InvoiceMetadata))]
    public partial class Invoice
    {
        // Note this class has nothing in it.  It's just here to add the class-level attribute.
    }

    public class InvoiceMetadata
    {
        // Name the field the same as EF named the property - "FirstName" for example.
        // Also, the type needs to match.  Basically just redeclare it.
        // Note that this is a field.  I think it can be a property too, but fields definitely should work.

        [HiddenInput]
        public int ID { get; set; }

        [Required]
        [UIHint("InvoiceType")]
        [Display(Name = "Invoice Type")]
        public string Status { get; set; }


        [DisplayFormat(NullDisplayText = "(null value)")]
        public Supplier Supplier { get; set; }

    }

UhintInvoiceType会导致为此InvoiceType模板加载element.This编辑器模板，定义如下

@model System.String

@{
      IDictionary<string, string> myDictionary = new Dictionary<string, string> { 
                                                                                        { "N", "New" }
                                                                                        , { "A", "Approved" },
                                                                                        {"H","On Hold"}
                                                                                        };

      SelectList projecttypes= new SelectList(myDictionary,"Key","Value");

       @Html.DropDownListFor(model=>model,projecttypes)     

 }

我的程序中有许多这样的硬编码状态列表，我之所以说硬编码，是因为它们不是从数据库中获取的。有没有其他方法可以为下拉菜单创建模板？如何在模型中声明枚举，并让下拉菜单加载枚举，而不必通过视图模型？

Answer 1

我不会对状态进行“硬编码”，而是创建一个Enum或一个Type Safe Enum。对于您的示例，我将使用后者。

对于每个所需的“状态列表”，使用所需的设置创建一个单独的类：

public sealed class Status
{
    private readonly string _name;
    private readonly string _value;

    public static readonly Status New = new Status("N", "New");
    public static readonly Status Approved = new Status("A", "Approved");
    public static readonly Status OnHold = new Status("H", "On Hold");

    private Status(string value, string name)
    {
        _name = name;
        _value = value;
    }

    public string GetValue()
    {
        return _value;
    }

    public override string ToString()
    {
        return _name;
    }

}

利用反射，您现在可以获取该类的字段来创建所需的下拉列表。创建一个扩展方法或助手类对您的项目是有好处的：

var type = typeof(Status);
var fields = type.GetFields(BindingFlags.Public | BindingFlags.Static | BindingFlags.DeclaredOnly);

Dictionary<string, string> dictionary = fields.ToDictionary(
    kvp => ((Status)kvp.GetValue(kvp)).GetValue(), 
    kvp => kvp.GetValue(kvp).ToString()
    );

您现在可以创建选择列表，就像您当前所做的那样：

var list = new SelectList(dictionary,"Key","Value");

这将创建一个包含以下html的下拉列表：

<select>
  <option value="N">New</option>
  <option value="A">Approved</option>
  <option value="H">On Hold</option>
</select>