C#: How to convert int to enum?

Cast int to enum

To convert into to enum in C#, use the cast operator.

The cast operator is pair of round brackets with the type that we want to convert to.

For example:

public enum Grade : int
{
    A = 5,
    B = 4,
    C = 3,
    D = 2,
    F = 1,
}
Grade grade = (Grade)5;
Console.WriteLine(grade); // A

In the example above, we casted the integer 5 to Grade enum A.

Underlying types

We can cast (convert) int to enum because enum's underlying value is integer-based.

For example, if we try to use a decimal as an underlying type, we will get an error:

public enum Weight : decimal
{
    Heavy = 1.0m,
}

Error: error CS1008: Type byte, sbyte, short, ushort, int, uint, long, or ulong expected

public enum Weight : byte
{
    Heavy = 1,
}

To learn how to use string enums, read this article.

Type safety

We need to be careful when casting enums because enums don't have compile or runtime checks for supporting values. For example:

public enum Grade : int
{
    A = 5,
    B = 4,
    C = 3,
    D = 2,
    F = 1,
}
Grade grade = (Grade)6;
Console.WriteLine(grade); // 6 

In the code above, we don't get an error about the integer that we're casting being out of defined enum values.

To check if enum value is valid in C#, use on of the methods:

• Enum.IsDefined(Type enumType, object value)
• Enum.IsDefined<TEnum>(TEnum value)
• Type.IsEnumDefined

Enum.IsDefined is a static method. The method returns true if the integer value is in supported range:

public enum Grade : int
{
    A = 5,
    B = 4,
    C = 3,
    D = 2,
    F = 1,
}
Console.WriteLine(Enum.IsDefined((Grade)6)); // False
Console.WriteLine(Enum.IsDefined((Grade)5)); // True

Console.WriteLine(Enum.IsDefined((Grade)5)); // True
Console.WriteLine(Enum.IsDefined((Grade)5)); // True

typeof(Grade).IsEnumDefined(5);

So, before we cast, we need to verify that enum is in supported range.

Extension method

Use this extension method to safely cast int to enums:

public static class ExtensionMethods
{
    public static TEnum ToEnum<TEnum>(this int value)
    {
        if (typeof(TEnum).IsEnumDefined(value))
            return (TEnum)(object)value;

        return default;
    }
}
Console.WriteLine(5.ToEnum<Grade>()); // A
Console.WriteLine(6.ToEnum<Grade>()); // 0

The extension method above safely converts int to enum. The method returns default value if enum doesn't have corresponding int value.