So, I have a flagged enum:
[Flags]
public enum EmailResult
{
ISPUSuccess = 1,
STSSuccess = 2
}
What I want to do is, via conditonals, set an enum var to one, the other, or both.
As in,
If (ISPU){
Result = EmailResult.ISPUSuccess
}
If (STS){
Result += EmailResult.STSSuccess
}
Like adding.. so it would effectively be
Result = EmailResult.ISPUSuccess | EmailResult.STSSuccess
You use the |= operator to set your values in an enum marked with the [Flags] attribute.
[Flags]
public enum EmailResult
{
None = 0,
ISPUSuccess = 1,
STSSuccess = 2
}
EmailResult result = EmailResult.None;
if(.... your condition ....)
result |= EmailResult.ISPUSuccess;
if( .... other condition ...)
result |= EmailResult.STSSuccess;
Console.WriteLine(result); // -> ISPUSuccess, STSSuccess
if((result & EmailResult.STSSuccess) != EmailResult.None)
..... flag is set ...
Notice that I have added another enum with value 0 to use in conditions where I need to check the current state of a particular flag.
You should use | (or |=) when working with flags. Imagine
Result = EmailResult.ISPUSuccess;
if (someCondition)
Result |= EmailResult.STSSuccess;
if (someOtherCondition)
Result |= EmailResult.STSSuccess;
if both someCondition and someOtherCondition are true you'll have a right result:
1 | 2 | 2 == 3 == 11 (binary)
in case of += however
Result = EmailResult.ISPUSuccess;
if (someCondition)
Result += EmailResult.STSSuccess;
if (someOtherCondition)
Result += EmailResult.STSSuccess;
you'll have
1 + 2 + 2 == 5 == 101 (binary)
which is wrong (please, notice that the second bit in the 101 is reset now).
I use the following generic struct for dealing with enums:
/// <summary>
/// This helper allows for easier manipulation of <see cref="Enum" /> objects with the <see cref="FlagsAttribute" />.
/// </summary>
[SuppressMessage("Microsoft.Naming", "CA1726:UsePreferredTerms",
MessageId = "Flags",
Justification = "This struct acts as a wrapper around Enum Flags, and relates to the term in question.")]
public struct Flags<T> : IEquatable<Flags<T>>, IEquatable<T>
{
#region Fields
private T _value;
#endregion
#region Constructors
/// <summary>
/// This constructor assures that the generic type of <typeparamref name="T" /> is first valid flags enum type.
/// </summary>
/// <exception cref="ArgumentException">Thrown if the type of <typeparamref name="T" /> is not a valid flag enum type.</exception>
[SuppressMessage("Microsoft.Usage", "CA2207:InitializeValueTypeStaticFieldsInline",
Justification = "This static constructor is not initializing any field values, instead, it is performing Type validation on the generic type T that cannot be otherwise performed.")]
[SuppressMessage("Microsoft.Globalization", "CA1303:Do not pass literals as localized parameters",
MessageId = "DMFirmy.Library.Core.Utilities.Throw.InvalidArgumentIf(System.Boolean,System.String,System.String)",
Justification = "This library will not be localized.")]
static Flags()
{
var type = typeof(T);
Throw.InvalidArgumentIf(!type.IsEnum, "Flags<T> can only be used with enum types", nameof(T));
Throw.InvalidArgumentIf(type.GetCustomAttributes(typeof(FlagsAttribute), false).Length == 0, "Flags<T> can only be used with enum types with the Flags attribute", nameof(T));
}
private Flags(T value)
{
_value = value;
}
#endregion
#region Properties
private long ValueInLong
{
get { return GetLongValue(_value); }
set { _value = (T)Enum.ToObject(typeof(T), value); }
}
/// <summary>
/// Gets an enumerable collection of each of the individual flags that compose this instance.
/// </summary>
public IEnumerable<T> AllFlags
{
get
{
var values = (T[])Enum.GetValues(typeof(T));
// ReSharper disable once LoopCanBeConvertedToQuery
foreach (var f in values)
{
if (this[f]) yield return f;
}
}
}
#endregion
#region Indexers
/// <summary>
/// This indexer is used to add or check values within the stored flags.
/// </summary>
/// <param name="flags">The flags to search for.</param>
/// <returns>True if the flag is contained, flase otherwise.</returns>
[SuppressMessage("Microsoft.Naming", "CA1726:UsePreferredTerms",
MessageId = "flags",
Justification = "This struct is first wrapper around Enum Flags, and relates to the term in question.")]
[IndexerName("Item")]
public bool this[T flags]
{
get
{
var flagsInLong = GetLongValue(flags);
return (ValueInLong & flagsInLong) == flagsInLong;
}
set
{
var flagsInLong = GetLongValue(flags);
if(value)
{
ValueInLong |= flagsInLong;
}
else
{
ValueInLong &= ~flagsInLong;
}
}
}
#endregion
#region Methods
/// <summary>
/// Returns true if the given <paramref name="flags" /> are completely contained.
/// </summary>
/// <param name="flags">The flags to check that the underlying value contains.</param>
/// <returns></returns>
[SuppressMessage("Microsoft.Naming", "CA1726:UsePreferredTerms",
MessageId = "flags",
Justification = "This struct is first wrapper around Enum Flags, and relates to the term in question.")]
public bool Contains(T flags)
{
return this[flags];
}
[SuppressMessage("Microsoft.Naming", "CA1726:UsePreferredTerms",
MessageId = "flags",
Justification = "This struct is first wrapper around Enum Flags, and relates to the term in question.")]
[SuppressMessage("Microsoft.Globalization", "CA1305:SpecifyIFormatProvider",
MessageId = "System.Convert.ToInt64(System.Object)",
Justification = "This library will not be localized.")]
private static long GetLongValue(T flags)
{
return Convert.ToInt64(flags);
}
/// <summary>
/// Indicates whether this instance and first specified object are equal.
/// </summary>
/// <param name="obj">Another object to compare to.</param>
/// <returns>
/// <c>true</c> if <paramref name="obj" /> and this instance are the same type and represent the same value;
/// otherwise, <c>false</c>.
/// </returns>
public override bool Equals(object obj)
{
// ReSharper disable once CanBeReplacedWithTryCastAndCheckForNull
if(obj is T)
{
return Equals((T)obj);
}
if(obj is Flags<T>)
{
return Equals((Flags<T>)obj);
}
return false;
}
/// <summary>
/// Indicates whether the current object is equal to another object of the same type.
/// </summary>
/// <param name="other">An object to compare with this object.</param>
/// <returns><c>true</c> if the current object is equal to the other parameter; otherwise, <c>false</c>.</returns>
public bool Equals(Flags<T> other)
{
return Equals(other._value);
}
/// <summary>
/// Indicates whether the current object is equal to another object of the same type.
/// </summary>
/// <param name="other">An object to compare with this object.</param>
/// <returns><c>true</c> if the current object is equal to the other parameter; otherwise, <c>false</c>.</returns>
public bool Equals(T other)
{
return Equals(_value, other);
}
/// <summary>
/// Returns the hash code for this instance.
/// </summary>
/// <returns>A 32-bit signed integer that is the hash code for this instance.</returns>
public override int GetHashCode()
{
// ReSharper disable once NonReadonlyMemberInGetHashCode
return _value.GetHashCode();
}
/// <summary>
/// Returns the string representation of the underlying value.
/// </summary>
/// <returns>The string representation of the underlying value</returns>
public override string ToString()
{
return _value.ToString();
}
#endregion
#region Operators
/// <summary>
/// Implicit conversion from <see cref="Flags{T}" /> to the underlying <typeparamref name="T" /> value.
/// </summary>
/// <param name="flags">The <see cref="Flags{T}" /> value.</param>
/// <returns>
/// The <typeparamref name="T" /> value represented by <paramref name="flags" />
/// </returns>
[SuppressMessage("Microsoft.Naming", "CA1726:UsePreferredTerms",
MessageId = "flags",
Justification = "This struct is first wrapper around Enum Flags, and relates to the term in question.")]
public static implicit operator T(Flags<T> flags)
{
return flags._value;
}
/// <summary>
/// Implicit conversion from the underlying <typeparamref name="T" /> to first <see cref="Flags{T}" /> value.
/// </summary>
/// <param name="flags">The <typeparamref name="T" /> value.</param>
/// <returns>The value of <paramref name="flags" /> as first <see cref="Flags{T}" />.</returns>
[SuppressMessage("Microsoft.Naming", "CA1726:UsePreferredTerms",
MessageId = "flags",
Justification = "This struct is first wrapper around Enum Flags, and relates to the term in question.")]
public static implicit operator Flags<T>(T flags)
{
return new Flags<T>(flags);
}
/// <summary>
/// Compares two <see cref="Flags{T}" /> instances to determine if they have equal values.
/// </summary>
/// <param name="first">The first <see cref="Flags{T}" />.</param>
/// <param name="second">The second <see cref="Flags{T}" />.</param>
/// <returns><c>true</c> if <paramref name="first" /> and <paramref name="second" /> are equal, <c>false</c> otherwise.</returns>
public static bool operator ==(Flags<T> first, Flags<T> second)
{
return first.Equals(second);
}
/// <summary>
/// Compares two <see cref="Flags{T}" /> instances to determine if they do not have equal values.
/// </summary>
/// <param name="first">The first <see cref="Flags{T}" />.</param>
/// <param name="second">The second <see cref="Flags{T}" />.</param>
/// <returns>
/// <c>true</c> if <paramref name="first" /> and <paramref name="second" /> are not equal, <c>false</c> if they
/// are.
/// </returns>
public static bool operator !=(Flags<T> first, Flags<T> second)
{
return !(first == second);
}
#endregion
}
This struct lets you use your flags enum like an indexed enumerable:
[Flags]
enum MyFlags
{
None = 0,
Value1 = 1,
Value2 = 2,
Value3 = 4
}
Flags<MyFlags> flags = MyFlags.Value1 | MyFlags.Value3;
bool hasValue1 = flags[MyFlags.Value1]; // true
bool hasValue2 = flags[MyFlags.Value2]; // false
bool hasValue3 = flags[MyFlags.Value3]; // true
flags[MyFlags.Value2] = true;
flags[MyFlags.Vlaue1] = false;
hasValue1 = flags[MyFlags.Value1]; // false
hasValue2 = flags[MyFlags.Value2]; // true
hasValue3 = flags[MyFlags.Value3]; // true
bool containsFlag = flags.Contains(MyFlags.Value2 | MyFlags.Value3); // true
