CODEWITHSUNDEEP
c#enumsdefault-value
AngieM
AngieM

Reputation: 745

Enum not default to 0 when not defined

I have an enum type defined as follows:

public enum OperationTypeEnum : byte
{
    /// <remarks/>
    @__NONE = 0,

    /// <remarks/>
    Sale = 1,

    /// <remarks/>
    Auth = 2
}

In my code, I cast an integer like so:

var operationType = (OperationTypeEnum) anotherIntVariable;

When anotherIntVariable is something undefined (e.g. 5), I am hoping to get 0 or __NONE back (since 5 is not defined as one of the valid enum values, but I receive 5 instead.

What do I need to change to make undefined enum values to be 0?

Thanks!

Upvotes: 0

Views: 2931

Answers (5)

Dev-lop-er
Dev-lop-er

Reputation: 728

#If your enum class is defined as below.

    public enum CategoryEnum : int
    {
        Undefined = 0,
        IT= 1,
        HR= 2,
        Sales= 3,
        Finance=4
    }

Now if you want to find Undefined enum if value doesnot match 1,2,3,4 then using the following Enum.IsDefine() function

Enum.IsDefined(typeof(CategoryEnum), request.CategoryId)

#returns true if id matches any enum values
#else returns false

Now for parsing the enum values as string


public enum Mode
    {
        UNDEFINED = 0,
        APP = 1,
        TEXT = 2,
    }

var value = Enum.TryParse(request.Mode, true, out Mode mode);
#returns mode enum

#Now to get Corresponding value for id or vice-vera, have an extension method as below:

  public static T AsEnum<T>(this string input) where T : struct, IConvertible
        {

            if (!typeof(T).IsEnum)
            {
                throw new ArgumentException("T must be an enumerated type");
            }

            Enum.TryParse(input, ignoreCase: true, out T result);

            return (T)result;

        }
  • Then fetch it using AsEnum() function:
var status = searchText.AsEnum<StatusEnum>();

Upvotes: 0

Artiom
Artiom

Reputation: 7837

The answer was given by @plast1k.

Here is a generic extension for your problem

public static class OperationTypeEnumExtensions
{
    public static T ToEnum<T>(this byte val) where T : struct
    {
        if(Enum.IsDefined(typeof(T), val)) 
            return (T) Enum.Parse(typeof(T), val.ToString());
        return default(T);
    }
}

usage

value.ToEnum<OperationTypeEnum>()

Upvotes: 2

Harald Coppoolse
Harald Coppoolse

Reputation: 30464

The safest method is to create an extension method for your enum class that will compare the enum values and if none of them initialize to @__NONE

If you are certain there are only a limited amount of enum values:

public static class OperationTypeEnumExtensions
{
    public static OperationTypeEnum ToOperationTypeEnum(this int val)
    {
        switch (val)
        {
            case (int) OperatinTypeEnum.Sale:
                return OperationTypeEnum.Sale;

            cast (int) OperationTypeEnum.Auth:
                return OperationTypeenum.Auth;

             default:
                return OperationTypeEnum.@_none;
        }
    }
}

Usage:

int myInt = GetMyIntValue();
OperationTypeEnum myEnum = myInt.ToOperationTypeEnum();

Upvotes: 0

plast1k
plast1k

Reputation: 843

C# enums are effectively integers and there are no compile or run time checks that you are using a "valid" value from your defined enum set. See this answer for more information https://stackoverflow.com/a/6413841/1724034

Upvotes: 1

crashmstr
crashmstr

Reputation: 28573

If you get a numerical value and need to only get actual enum values, you can use Enum.TryParse

The example displays the following output:
Converted '0' to None.
Converted '2' to Green.
8 is not an underlying value of the Colors enumeration.
blue is not a member of the Colors enumeration.
Converted 'Blue' to Blue.
Yellow is not a member of the Colors enumeration. 

using System;

[Flags] enum Colors { None=0, Red = 1, Green = 2, Blue = 4 };

public class Example
{
    public static void Main()
    {
       string[] colorStrings = { "0", "2", "8", "blue", "Blue", "Yellow", "Red, Green" };
       foreach (string colorString in colorStrings)
       {
          Colors colorValue;
          if (Enum.TryParse(colorString, out colorValue))        
             if (Enum.IsDefined(typeof(Colors), colorValue) | colorValue.ToString().Contains(","))  
                Console.WriteLine("Converted '{0}' to {1}.", colorString, colorValue.ToString());
             else
                Console.WriteLine("{0} is not an underlying value of the Colors enumeration.", colorString);
          else
             Console.WriteLine("{0} is not a member of the Colors enumeration.", colorString);
       }
    }
}

Upvotes: 0

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