我們要做到這一點,在過去幾次一樣,所以我們建立了一些擴展方法(上的int,long等等)來幫助我們。所有這些的核心是在單一的靜態通用TryAsEnum方法實現:
/// <summary>
/// Helper method to try to convert a value to an enumeration value.
///
/// If <paramref name="value"/> is not convertable to <typeparam name="TEnum"/>, an exception will be thrown
/// as documented by Convert.ChangeType.
/// </summary>
/// <param name="value">The value to convert to the enumeration type.</param>
/// <param name="outEnum">The enumeration type value.</param>
/// <returns>true if value was successfully converted; false otherwise.</returns>
/// <exception cref="InvalidOperationException">Thrown if <typeparamref name="TEnum"/> is not an enum type. (Because we can't specify a generic constraint that T is an Enum.)</exception>
public static bool TryAsEnum<TValue, TEnum>(TValue value, out TEnum outEnum) where TEnum : struct
{
var enumType = typeof(TEnum);
if (!enumType.IsEnum)
{
throw new InvalidOperationException(string.Format("{0} is not an enum type.", enumType.Name));
}
var valueAsUnderlyingType = Convert.ChangeType(value, Enum.GetUnderlyingType(enumType));
if (Enum.IsDefined(enumType, valueAsUnderlyingType))
{
outEnum = (TEnum) Enum.ToObject(enumType, valueAsUnderlyingType);
return true;
}
// IsDefined returns false if the value is multiple composed flags, so detect and handle that case
if(enumType.GetCustomAttributes(typeof(FlagsAttribute), inherit: true).Any())
{
// Flags attribute set on the enum. Get the enum value.
var enumValue = (TEnum)Enum.ToObject(enumType, valueAsUnderlyingType);
// If a value outside the actual enum range is set, then ToString will result in a numeric representation (rather than a string one).
// So if a number CANNOT be parsed from the ToString result, we know that only defined values have been set.
decimal parseResult;
if(!decimal.TryParse(enumValue.ToString(), out parseResult))
{
outEnum = enumValue;
return true;
}
}
outEnum = default(TEnum);
return false;
}
此實現處理與[旗]屬性定義與任何基本類型枚舉,以及枚舉。
如何獲得'Converter'中的枚舉類型? – Rachel