Check if unknown enum has default value

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I have a few enums and all have the first with the Name "Default". Now I have a function where I only get an onject as Parameter so how can I check if this object is set to the first entry of the enum? I only know how to check if it is a enum but not what value it has.

Something like this would help I geuss

public static bool IsFirstEnum<T>(T enumVal) where T: System.Enum
{
    return enumVal.Equals(default(T));
}

PS: Please keep in mind that default Enum element is defined first with lowest Flag (Preferably 0) Ref

Ex: enum Day {Sat, Sun, Mon, Tue, Wed, Thu, Fri}; where Sat is Default Ex: enum Day {Sat=1, Sun, Mon, Tue, Wed, Thu, Fri}; where againg Sat is Default Ex: enum Day {Sat=1, Sun=0, Mon, Tue, Wed, Thu, Fri}; where againg Sun is Default

If your intention is to use "Defaul" keyword then

public static bool IsDefaultEnum<T>(T enumVal) where T: System.Enum
{ 
    var val = typeof(T).GetField("Default").GetValue(enumVal);
    return val.Equals(enumVal);
}

Default value for unknown Enum value · Issue #90 · Kotlin/kotlinx , a default value for a deserialized Enum field, if an unknown value is enum class Status { ACTIVE, INACTIVE, UNKNOWN } class Test(val  @unknown default basically works the same as the regular default and therefore, matches any value. The main difference is that the compiler will produce a warning if all known elements of the enum have not yet been matched. New enum cases remain source-compatible as a result of throwing a warning instead of an error.

If all of these default values are zero (which is the norm) then you can just cast to int and compare with zero. This is also the same as default for the given enum type.

If not and you want to use the name "Default" as the determining feature then you could use.

Enum.Parse(typeof(MyEnum), "Default")

To return an object equal to MyEnum.Default and so on.

To obtain the first defined value you would need to use:

typeof(MyEnum).GetFields(BindingFlags.Static | BindingFlags.Public).First().GetValue(null);

I'm not sure if it's guaranteed that the first defined value would remain the first in order, but it currently works that way.

Enum.IsDefined(Type, Object) Method (System), public static bool IsDefined (Type enumType, object value); The type of value is an enumeration, but it is not an enumeration of type enumType . To determine whether multiple bit fields are set in an enumeration type that is tagged with the  The default value of an uninitialized enumeration, just like other value types, is zero. A non-flags-attributed enumeration should define a member that has the value of zero so that the default value is a valid value of the enumeration. If appropriate, name the member 'None'. Otherwise, assign zero to the most frequently used member. By default, if the value of the first enumeration member is not set in the declaration, its value is zero.

You can cast int values into Enum values (and reversed), and the default Enum value always has a value of 0.

You can check if a returned enum is the default value by checking it's int value:

if((int)EnumVal == 0)
{return "Enum is default";}

the other way around, you can check what the default is by casting the other way around:

    EnumName default = (EnumName)0;

How can I ignore unknown enum values during json deserialization?, How can I get Json.net not to throw up when my enum doesn't match string value which is not defined in the enum com Map key of type com. from String "Test": not Jackson JSON, The default enum element value is used if unknown value  You can use one of two methods: default enum value or a nullable enum. Default enum value. Since an enum is backed by an integer, and int defaults to zero, the enum will always initialize by default to the value equivalent to zero. Unless you explicitly assign enum values, the first value will always be zero, second will be one, and so on.

ENUM statement - Documentation, The value of a variable defined as an enum is restricted to the list of members defined By default, the compiler sets those associated values automatically. references, variables defined as enums have an initial value of the unknown (?) with the CASE statement, but be aware that the WHEN phrases check for equality  “By default, the first enumerator has the value 0, and the value of each successive enumerator is increased by 1.” “The value type enum has the value produced by the expression (E)0, where E is the enum identifier.“ You can check the documentation for C# enum here, and the documentation for C# default values table here.

Assigning a default value if one doesnt exist in enum, I wanted to know if it was possible to set a default value for a enum EXAMPLE5 is there a way I can default it to have a value of Example. No matter what, a given enum will be created with the literal value 0. The most straight forward case here is as a member of a struct. A C# struct will always have an empty default constructor that initalizes all fields to their default value. In the case of an enum, that will be the literal value 0.

DeserializationFeature (jackson-databind 2.6.0 API), Feature that allows unknown Enum values to be parsed as null values. Accessor for checking whether this feature is enabled by default. boolean  In the case of a need to represent unknown values, an extra enum-member sounds good as a solution. In case of a need to represent absence of any value, make it nullable. Have in mind, that there is nothing wrong with having both “unknown” enum-member and the enum itself being nullable at the same time. HTH.

Comments
  • Could you please provide a short code-sample that shows what you triy to achieve?
  • "I only get an onject as Parameter" what kind of object, System.Object? If so, why? You don't know the type of enum that is passed?
  • Yes, I dont know the type of enum that I get, I only want to know if it is set to the first value.
  • Did you try to use Enum.TryParse?
  • The default value of all enums is the one with converted integer value 0. But you may also be talking about an enum with a tag Default where this tag is not 0 (which is not recommended practice, but it is allowed).
  • As an asside: the enum-constraint exists only from C#7.3 upwards.
  • Could you please explain this "Please keep in mind that default Enum element is defined fist with lowest Flag"?
  • The information "default Enum element is defined first with lowest Flag" is wrong. default(SomeEnumType) will always return 0. Even if the Enumeration doesn't have an element with value 0.
  • This code checks if the value is 0, regardless of whether this value has been assigned a tag or not, or whether this tag is the first one. In particular, for the enum enum Day {Sat=1, Sun, Mon, Tue, Wed, Thu, Fri}, none of the defined tags qualify as the "default" with this code (and, indeed, none of them are!)
  • Lower values can appear after higher values if explicitly set. Whether that's a good, bad or irrelevant thing for the question isn't clear.
  • Technically the C# standard does not make guarantees about the physical order of members for any type, enum or not, except that the declaration order is respected for assigning enum tag values and the order in which initializers are called, so no, this isn't guaranteed. Practically, it respects the order, and it needs to for things like StructLayoutKind(LayoutKind.Sequential). Still, probably not something you want code to depend on (there's probably someone out there who thought it'd be neat to have an editor extension to sort enum values alphabetically or by value, which is "safe"...)
  • according to documentation this is not always true
  • default is reserved word and it cannot be used as variable :)