/// <exception cref="FormatException">Thrown if a flag name is empty.</exception>
public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
{
if (value is string stringValue)
{
try
{
return(FlagsEnum.ParseKnownFlags(EnumType, stringValue));
}
catch (Exception ex)
{
// Matches the exception type thrown by EnumTypeConverter.
throw new FormatException(PipelinesWebApiResources.InvalidFlagsEnumValue(stringValue, EnumType), ex);
}
}
return(base.ConvertFrom(context, culture, value));
}
/// <summary>
/// Parse known enum flags in a comma-separated string. Unknown flags are ignored. Allows for degraded compatibility without serializing enums to integers.
/// </summary>
/// <remarks>
/// Case insensitive. Both standard and EnumMemberAttribute names are parsed.
/// </remarks>
/// <exception cref="NullReferenceException">Thrown if stringValue is null.</exception>
/// <exception cref="ArgumentException">Thrown if a flag name is empty.</exception>
public static object ParseKnownFlags(Type enumType, string stringValue)
{
ArgumentUtility.CheckForNull(enumType, nameof(enumType));
if (!enumType.IsEnum)
{
throw new ArgumentException(PipelinesWebApiResources.FlagEnumTypeRequired());
}
// Check for the flags attribute in debug. Skip this reflection in release.
Debug.Assert(enumType.GetCustomAttributes(typeof(FlagsAttribute), inherit: false).Any(), "FlagsEnum only intended for enums with the Flags attribute.");
// The exception types below are based on Enum.TryParseEnum (http://index/?query=TryParseEnum&rightProject=mscorlib&file=system%5Cenum.cs&rightSymbol=bhaeh2vnegwo)
if (stringValue == null)
{
throw new ArgumentNullException(stringValue);
}
if (String.IsNullOrWhiteSpace(stringValue))
{
throw new ArgumentException(PipelinesWebApiResources.NonEmptyEnumElementsRequired(stringValue));
}
if (UInt64.TryParse(stringValue, NumberStyles.AllowLeadingSign, CultureInfo.InvariantCulture, out ulong ulongValue))
{
return(Enum.Parse(enumType, stringValue));
}
var enumNames = Enum.GetNames(enumType).ToHashSet(name => name, StringComparer.OrdinalIgnoreCase);
var enumMemberMappings = new Lazy <IDictionary <string, string> >(() =>
{
IDictionary <string, string> mappings = null;
foreach (var field in enumType.GetFields())
{
if (field.GetCustomAttributes(typeof(EnumMemberAttribute), false).FirstOrDefault() is EnumMemberAttribute enumMemberAttribute)
{
if (mappings == null)
{
mappings = new Dictionary <string, string>(StringComparer.OrdinalIgnoreCase);
}
mappings.Add(enumMemberAttribute.Value, field.GetValue(null).ToString());
}
}
return(mappings);
});
var values = stringValue.Split(s_enumSeparatorCharArray);
var matches = new List <string>();
for (int i = 0; i < values.Length; i++)
{
string value = values[i].Trim();
if (String.IsNullOrEmpty(value))
{
throw new ArgumentException(PipelinesWebApiResources.NonEmptyEnumElementsRequired(stringValue));
}
if (enumNames.Contains(value))
{
matches.Add(value);
}
else if (enumMemberMappings.Value != null && enumMemberMappings.Value.TryGetValue(value, out string matchingValue))
{
matches.Add(matchingValue);
}
}
if (!matches.Any())
{
return(Enum.Parse(enumType, "0"));
}
string matchesString = String.Join(", ", matches);
return(Enum.Parse(enumType, matchesString, ignoreCase: true));
}
