数据将枚举属性绑定到网格并显示描述

Question

这是与How to bind a custom Enum description to a DataGrid 类似的问题，但就我而言，我有多个属性。

public enum ExpectationResult
{
    [Description("-")]
    NoExpectation,

    [Description("Passed")]
    Pass,

    [Description("FAILED")]
    Fail
}

public class TestResult
{
    public string TestDescription { get; set; }
    public ExpectationResult RequiredExpectationResult { get; set; }
    public ExpectationResult NonRequiredExpectationResult { get; set; }
}

我将 BindingList 绑定到 WinForms DataGridView（实际上是 DevExpress.XtraGrid.GridControl，但通用解决方案将更广泛适用）。我希望出现描述而不是枚举名称。我怎样才能做到这一点？ （对类/枚举/属性没有限制；我可以随意更改它们。）

Answer 1

TypeConverter 通常会完成这项工作；这是一些适用于DataGridView 的代码 - 只需添加您的代码以阅读描述（通过反射等 - 我现在只是使用字符串前缀来显示自定义代码的工作）。

请注意，您可能也想覆盖 ConvertFrom。转换器可以在类型 或 属性级别指定（如果您只希望它应用于某些属性），如果枚举不受您的控制，也可以在运行时应用。

using System.ComponentModel;
using System.Windows.Forms;
[TypeConverter(typeof(ExpectationResultConverter))]
public enum ExpectationResult
{
    [Description("-")]
    NoExpectation,

    [Description("Passed")]
    Pass,

    [Description("FAILED")]
    Fail
}

class ExpectationResultConverter : EnumConverter
{
    public ExpectationResultConverter()
        : base(
            typeof(ExpectationResult))
    { }

    public override object ConvertTo(ITypeDescriptorContext context,
        System.Globalization.CultureInfo culture, object value,
        System.Type destinationType)
    {
        if (destinationType == typeof(string))
        {
            return "abc " + value.ToString(); // your code here
        }
        return base.ConvertTo(context, culture, value, destinationType);
    }
}

public class TestResult
{
    public string TestDescription { get; set; }
    public ExpectationResult RequiredExpectationResult { get; set; }
    public ExpectationResult NonRequiredExpectationResult { get; set; }

    static void Main()
    {
        BindingList<TestResult> list = new BindingList<TestResult>();
        DataGridView grid = new DataGridView();
        grid.DataSource = list;
        Form form = new Form();
        grid.Dock = DockStyle.Fill;
        form.Controls.Add(grid);
        Application.Run(form);
    }
}

Answer 2

我不确定这有多大帮助，但我在 Enum 上使用了一个扩展方法，如下所示：

    /// <summary>
    /// Returns the value of the description attribute attached to an enum value.
    /// </summary>
    /// <param name="en"></param>
    /// <returns>The text from the System.ComponentModel.DescriptionAttribute associated with the enumeration value.</returns>
    /// <remarks>
    /// To use this, create an enum and mark its members with a [Description("My Descr")] attribute.
    /// Then when you call this extension method, you will receive "My Descr".
    /// </remarks>
    /// <example><code>
    /// enum MyEnum {
    ///     [Description("Some Descriptive Text")]
    ///     EnumVal1,
    ///
    ///     [Description("Some More Descriptive Text")]
    ///     EnumVal2
    /// }
    /// 
    /// static void Main(string[] args) {
    ///     Console.PrintLine( MyEnum.EnumVal1.GetDescription() );
    /// }
    /// </code>
    /// 
    /// This will result in the output "Some Descriptive Text".
    /// </example>
    public static string GetDescription(this Enum en)
    {
        var type = en.GetType();
        var memInfo = type.GetMember(en.ToString());

        if (memInfo != null && memInfo.Length > 0)
        {
            var attrs = memInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);
            if (attrs != null && attrs.Length > 0)
                return ((DescriptionAttribute)attrs[0]).Description;
        }
        return en.ToString();
    }

您可以在对象上使用自定义属性 getter 来返回名称：

public class TestResult
{
    public string TestDescription { get; set; }
    public ExpectationResult RequiredExpectationResult { get; set; }
    public ExpectationResult NonRequiredExpectationResult { get; set; }

    /* *** added these new property getters *** */
    public string RequiredExpectationResultDescr { get { return this.RequiredExpectationResult.GetDescription(); } }
    public string NonRequiredExpectationResultDescr { get { return this.NonRequiredExpectationResult.GetDescription(); } }
}

然后将您的网格绑定到“RequiredExpectationResultDescr”和“NonRequiredExpectationResultDescr”属性。

这可能有点过于复杂，但这是我想出的第一件事:)

Answer 3

基于其他两个答案，我整理了一个类，该类可以使用每个枚举值的 Description 属性在任意枚举和字符串之间进行一般转换。

这里使用System.ComponentModel来定义DescriptionAttribute，只支持T和String的转换。

public class EnumDescriptionConverter<T> : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
    {
        return (sourceType == typeof(T) || sourceType == typeof(string));
    }

    public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
    {
        return (destinationType == typeof(T) || destinationType == typeof(string));
    }

    public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value)
    {
        Type typeFrom = context.Instance.GetType();

        if (typeFrom == typeof(string))
        {
            return (object)GetValue((string)context.Instance);
        }
        else if (typeFrom is T)
        {
            return (object)GetDescription((T)context.Instance);
        }
        else
        {
            throw new ArgumentException("Type converting from not supported: " + typeFrom.FullName);
        }
    }

    public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType)
    {
        Type typeFrom = value.GetType();

        if (typeFrom == typeof(string) && destinationType == typeof(T))
        {
            return (object)GetValue((string)value);
        }
        else if (typeFrom == typeof(T) && destinationType == typeof(string))
        {
            return (object)GetDescription((T)value);
        }
        else
        {
            throw new ArgumentException("Type converting from not supported: " + typeFrom.FullName);
        }
    }

    public string GetDescription(T en)
    {
        var type = en.GetType();
        var memInfo = type.GetMember(en.ToString());

        if (memInfo != null && memInfo.Length > 0)
        {
            var attrs = memInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);
            if (attrs != null && attrs.Length > 0)
                return ((DescriptionAttribute)attrs[0]).Description;
        }
        return en.ToString();
    }

    public T GetValue(string description)
    {
        foreach (T val in Enum.GetValues(typeof(T)))
        {
            string currDescription = GetDescription(val);
            if (currDescription == description)
            {
                return val;
            }
        }

        throw new ArgumentOutOfRangeException("description", "Argument description must match a Description attribute on an enum value of " + typeof(T).FullName);
    }
}