枚举扩展方法ToDataSource

不幸的是,你不能。扩展方法是一种功能,它允许您在类型的实例上调用新方法。它没有能力将此功能赋予类型本身。

当我想添加一组方法add type level时,我通常会创建一个名为OriginalTypeNameUtil的新静态类,并在其中添加方法。例如ResponseUtil。这样,当我键入原始类型名时,类名是可见的。

我只是做了一些类似的事情,没有扩展枚举类型,而是扩展了DataTable。

public static DataTable FromEnum(this DataTable dt, Type enumType) {
if (!enumType.IsEnum) { throw new ArgumentException("The specified type is not a System.Enum."); }
DataTable tbl = new DataTable();
string[] names = Enum.GetNames(enumType);
Array values = Enum.GetValues(enumType);
List<string> enumItemNames = new List<string>();
List<int> enumItemValues = new List<int>();
try {
    // build the table
    tbl.Columns.Add(new DataColumn("Value", typeof(string)));
    tbl.Columns.Add(new DataColumn("Text", typeof(string)));
    // Get the enum item names (using the enum item's description value if defined)
    foreach (string enumItemName in names) {
        enumItemNames.Add(((Enum)Enum.Parse(enumType, enumItemName)).ToDescription());
    }
    // Get the enum item values
    foreach (object itemValue in values) {
        enumItemValues.Add(Convert.ToInt32(Enum.Parse(enumType, itemValue.ToString())));
    }
    // Make sure that the data table is empty
    tbl.Clear();

    // Fill the data table
    for (int i = 0; i <= names.Length - 1; i++) {
        DataRow newRow = tbl.NewRow();
        newRow["Value"] = enumItemValues[i];
        newRow["Text"] = enumItemNames[i];
        tbl.Rows.Add(newRow);
    }
}
catch {
    tbl.Clear();
    tbl = dt;
}
// Return the data table to the caller
return tbl;

}

它的名字是这样的:

DataTable tbl = new DataTable().FromEnum(typeof(YourEnum));

似乎您只需要一个真正的静态方法和一个“类似枚举”的类:

public class Response
{
    public static readonly Response Yes = new Response(1);
    public static readonly Response No = new Response(2);
    public static readonly Response Maybe = new Response(3);

    int value;

    private Response(int value)
    {
        this.value = value;
    }

    public static DataTable ToDataSource()
    {
        // ...
    }
}

如果使用模拟枚举的结构:

   public struct Response
   {
     private int ival;
     private Response() {} // private ctor to eliminate instantiation
     private Response(int val) { ival = val; }
     private static readonly Response Yes = new Response(1);
     private static readonly Response No = new Response(2);
     private static readonly Response Maybe= new Response(3);
     // etc...  ...for whatever other functionality you want.... 
   }

然后这个结构的功能完全(接近完全!)像一个枚举,您可以向它添加扩展方法。。。

但是,您可以创建一个接受枚举的泛型函数,并从中创建一个表。

public static DataTable CreateDataSource<TEnum>()
{
    Type enumType = typeof(TEnum);

    if (enumType.IsEnum) // It is not possible to do "where TEnum : Enum"
    {
        DataTable table = new DataTable();
        table.Columns.Add("Name");
        table.Columns.Add("Value", enumType);

        foreach (var value in Enum.GetValues(enumType))
        {
            table.Rows.Add(Enum.GetName(enumType, value), value);
        }

        return table;
    }
    else
        throw new ArgumentException("Type TEnum is not an enumeration.");
}

string[] names = Enum.GetNames(typeof(Test));

Array test = Enum.GetValues(typeof(Test));
var vals = test.Cast<int>();

var source = from n in names
             from v in vals
             select new
             {
                 Text = n,
                 Value = v
             };

未测试,但速度很快:)