C# Globals/Constants 可绑定到 DDL，但具有“好”的名称

Question

出于通常的原因，我需要在我的应用程序中使用一些常量。

我考虑过的方法：

1) 声明一个枚举：

public enum myOptions
{
  MyOption1 = 72,
  MyOption2 = 31,
  MyOption3 = 44
}

虽然这很适合编程，而且我可以将枚举直接绑定到 DDL，但是当用户看到枚举“名称”时它们很难看 - 用户将看到“MyOption1”，我希望他们看到“我的选项 #1"。

2) 使用列表：

public static List<KeyValuePair<int, string>> myOptions = new List<KeyValuePair<int, string>>
{
 new KeyValuePair<int, string>(77, "My Option #1"),
 new KeyValuePair<int, string>(31, "My Option #2"),
 new KeyValuePair<int, string>(44, "My Option #3")
}

因此，虽然这很好地绑定到 DDL，给了我一个很好的显示值以及一个整数返回值，但我没有任何东西可以测试我的返回值。所以，例如：

if (selectedOption=????) //I'd have to hardcode the Key or Value I want to test for.

3) 我可以构建好的全局/常量程序集：

static myOptions
{
 public static KeyValuePair<int, string> MyOption1 = new new KeyValuePair<int, string>(77, "My Option #1");
 public static KeyValuePair<int, string> MyOption2 = new new KeyValuePair<int, string>(31, "My Option #2");
 public static KeyValuePair<int, string> MyOption3 = new new KeyValuePair<int, string>(44, "My Option #3");
}

这给了我很好的显示名称，很适合编写代码，但据我所知，我无法轻松地将它绑定到 DDL（我必须手动编写代码）。

有没有人有一种优雅的方式来创建易于绑定到 DDL 的常量，我可以在其中有一个漂亮的显示名称？

现在我唯一能想到的就是同时构建枚举和列表，这似乎很烦人。

Answer 1

我总是倾向于装饰枚举值：

public enum myOptions
{
    [Description("My Option #1")]
    MyOption1 = 72,
    [Description("My Option #2")]
    MyOption2 = 31,
    [Description("My Option #3")]
    MyOption3 = 44
}

或者更好的是，您可以创建一个绑定到资源文件或配置设置的自定义属性，以便无需重新编译即可更改此数据

public enum myOptions
{
    [Custom("MyOption1Key")]
    MyOption1 = 72,
    [Custom("MyOption2Key")]
    MyOption2 = 31,
    [Custom("MyOption3Key")]
    MyOption3 = 44
}

---

更新以从枚举中提取属性

public static T GetAttribute<T>(this Enum e) where T : Attribute
{
    FieldInfo fieldInfo = e.GetType().GetField(e.ToString());
    T[] attribs = fieldInfo.GetCustomAttributes(typeof(T), false) as T[];
    return attribs.Length > 0 ? attribs[0] : null;
}

Answer 2

根据@hunter 提供的答案，我决定发布我的完整实现，因为我花了一段时间才把它弄好（还在这里学习......）

// This is the class I used to hold the extensions.
public static class EnumFunctions
{
    // Custom GetAttribute Extension - used to pull an attribute out of the enumerations.
    // This code is as per Hunter's answer, except I added the null check.
    public static T GetAttribute<T>(this Enum e) where T : Attribute
    {
        FieldInfo fieldInfo = e.GetType().GetField(e.ToString());

        // If the enumeration is set to an illegal value (for example 0,
        // when you don't have a 0 in your enum) then the field comes back null.
        // test and avoid the exception.
        if (fieldInfo != null)
        {
            T[] attribs = fieldInfo.GetCustomAttributes(typeof(T), false) as T[];
            return attribs.Length > 0 ? attribs[0] : null;
        }
        else
        {
            return null;
        }
    }

    // Custom GetKeyValuePairs - returns a List of <int,string> key value pairs with
    // each Enum value along with it's Description attribute.
    // This will only work with a decorated Enum. I've not included or tested what
    // happens if your enum doesn't have Description attributes.
    public static List<KeyValuePair<int, string>> GetKeyValuePairs(this Enum e)
    {
        List<KeyValuePair<int, string>> ret = new List<KeyValuePair<int, string>>();

        foreach (Enum val in Enum.GetValues(e.GetType()))
        {
            ret.Add(new KeyValuePair<int, string>(Convert.ToInt32(val), val.GetAttribute<DescriptionAttribute>().Description));
        }
        return ret;
    }

}

在其他地方，要绑定到 DDL，您可以简单地这样做：

{
    // We need an instance of the enum to call our extension method.
    myOptions o = myOptions.MyOption1;

    // Clear the combobox
    comboBox1.DataSource = null;
    comboBox1.Items.Clear();

    // Bind the combobox
    comboBox1.DataSource = new BindingSource(o.GetKeyValuePairs(), null);
    comboBox1.DisplayMember = "Value";
    comboBox1.ValueMember = "Key";      
}

最后，要提取选定的值，您可以这样做：

{
    // Get the selected item in the combobox
    KeyValuePair<int, string> selectedPair = (KeyValuePair<int, string>)comboBox1.SelectedItem;

    //I'm just sticking the values into text labels to demonstrate.
    lblSelectedKey.Text = selectedPair.Key.ToString();
    lblSelectedValue.Text = selectedPair.Value.ToString();
}

..我并没有就此止步。我扩展了 ComboBox 控件本身，所以现在绑定它非常方便。

    // Extends the Combobox control so that it can be automatically bound to an Enum
    // that has been decorated with Description attributes.
    // Sets the current value of the combobox to the value of the enum instance passed in.
    public static void BindToDecoratedEnum(this System.Windows.Forms.ComboBox cb, Enum e)
    {
        // Clear the combobox
        cb.DataSource = null;
        cb.Items.Clear();

        // Bind the combobox
        cb.DataSource = new System.Windows.Forms.BindingSource(e.GetKeyValuePairs(), null);
        cb.DisplayMember = "Value";
        cb.ValueMember = "Key";

        cb.Text = e.GetAttribute<DescriptionAttribute>().Description;
    }

所以现在，每当我想填充 DDL 时，我只需：

        myDDL.BindToDecoratedEnum(myEnumInstanceWithValue);

代码绑定它，并选择与传入的Enum的当前值匹配的项。

欢迎对我的实施提出评论和批评（实际上，我会很感激 - 就像我说的，我正在努力学习......）

Answer 3

另一个建议？

public static List<KeyValuePair<int, string>> GetKeyValuePairs<T>()
    {
        Type enumType = typeof(T);

        List<KeyValuePair<int, string>> ret = new List<KeyValuePair<int, string>>();
        foreach (Enum val in Enum.GetValues(enumType))
        {
            ret.Add(
                new KeyValuePair<int, string>(Convert.ToInt32(val),
                val.GetAttribute<DescriptionAttribute>().Description)
                );
        } return ret;
    }

然后您可以绑定而无需创建枚举的实例。它是您想要了解的枚举类型，而不是特定实例）

ddlPes.DataSource = EnumHelper.GetKeyValuePairs<PesId>();
ddlPes.DataValueField = "key";
ddlPes.DataTextField = "value";
ddlPes.DataBind();