这是EnumTryParse 的自定义实现。与其他常见实现不同，它还支持使用Flags 属性标记的枚举。
/// <summary>
/// Converts the string representation of an enum to its Enum equivalent value. A return value indicates whether the operation succeeded.
/// This method does not rely on Enum.Parse and therefore will never raise any first or second chance exception.
/// </summary>
/// <param name="type">The enum target type. May not be null.</param>
/// <param name="input">The input text. May be null.</param>
/// <param name="value">When this method returns, contains Enum equivalent value to the enum contained in input, if the conversion succeeded.</param>
/// <returns>
/// true if s was converted successfully; otherwise, false.
/// </returns>
public static bool EnumTryParse(Type type, string input, out object value)
{
if (type == null)
throw new ArgumentNullException("type");
if (!type.IsEnum)
throw new ArgumentException(null, "type");
if (input == null)
{
value = Activator.CreateInstance(type);
return false;
}
input = input.Trim();
if (input.Length == 0)
{
value = Activator.CreateInstance(type);
return false;
}
string[] names = Enum.GetNames(type);
if (names.Length == 0)
{
value = Activator.CreateInstance(type);
return false;
}
Type underlyingType = Enum.GetUnderlyingType(type);
Array values = Enum.GetValues(type);
// some enums like System.CodeDom.MemberAttributes *are* flags but are not declared with Flags...
if ((!type.IsDefined(typeof(FlagsAttribute), true)) && (input.IndexOfAny(_enumSeperators) < 0))
return EnumToObject(type, underlyingType, names, values, input, out value);
// multi value enum
string[] tokens = input.Split(_enumSeperators, StringSplitOptions.RemoveEmptyEntries);
if (tokens.Length == 0)
{
value = Activator.CreateInstance(type);
return false;
}
ulong ul = 0;
foreach (string tok in tokens)
{
string token = tok.Trim(); // NOTE: we don't consider empty tokens as errors
if (token.Length == 0)
continue;
object tokenValue;
if (!EnumToObject(type, underlyingType, names, values, token, out tokenValue))
{
value = Activator.CreateInstance(type);
return false;
}
ulong tokenUl;
switch (Convert.GetTypeCode(tokenValue))
{
case TypeCode.Int16:
case TypeCode.Int32:
case TypeCode.Int64:
case TypeCode.SByte:
tokenUl = (ulong)Convert.ToInt64(tokenValue, CultureInfo.InvariantCulture);
break;
//case TypeCode.Byte:
//case TypeCode.UInt16:
//case TypeCode.UInt32:
//case TypeCode.UInt64:
default:
tokenUl = Convert.ToUInt64(tokenValue, CultureInfo.InvariantCulture);
break;
}
ul |= tokenUl;
}
value = Enum.ToObject(type, ul);
return true;
}
private static char[] _enumSeperators = new char[] { ',', ';', '+', '|', ' ' };
private static object EnumToObject(Type underlyingType, string input)
{
if (underlyingType == typeof(int))
{
int s;
if (int.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(uint))
{
uint s;
if (uint.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(ulong))
{
ulong s;
if (ulong.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(long))
{
long s;
if (long.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(short))
{
short s;
if (short.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(ushort))
{
ushort s;
if (ushort.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(byte))
{
byte s;
if (byte.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(sbyte))
{
sbyte s;
if (sbyte.TryParse(input, out s))
return s;
}
return null;
}
private static bool EnumToObject(Type type, Type underlyingType, string[] names, Array values, string input, out object value)
{
for (int i = 0; i < names.Length; i++)
{
if (string.Compare(names[i], input, StringComparison.OrdinalIgnoreCase) == 0)
{
value = values.GetValue(i);
return true;
}
}
if ((char.IsDigit(input[0]) || (input[0] == '-')) || (input[0] == '+'))
{
object obj = EnumToObject(underlyingType, input);
if (obj == null)
{
value = Activator.CreateInstance(type);
return false;
}
value = obj;
return true;
}
value = Activator.CreateInstance(type);
return false;
}