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CA1028: Enum storage should be Int32

TypeName

EnumStorageShouldBeInt32

CheckId

CA1028

Category

Microsoft.Design

Breaking Change

Breaking

The underlying type of a public enumeration is not System.Int32.

An enumeration is a value type that defines a set of related named constants. By default, the System.Int32 data type is used to store the constant value. Even though you can change this underlying type, it is not necessary or recommended for most scenarios. Note that no significant performance gain is achieved by using a data type that is smaller than Int32. If you cannot use the default data type, you should use one of the Common Language System (CLS)-compliant integral types, Byte, Int16, Int32, or Int64 to make sure that all values of the enumeration can be represented in CLS-compliant programming languages.

To fix a violation of this rule, unless size or compatibility issues exist, use Int32. For situations where Int32 is not large enough to hold the values, use Int64. If backward compatibility requires a smaller data type, use Byte or Int16.

Suppress a warning from this rule only if backward compatibility issues require it. In applications, failure to comply with this rule usually does not cause problems. In libraries, where language interoperability is required, failure to comply with this rule might adversely affect your users.

The following example shows two enumerations that do not use the recommended underlying data type.

using System;

namespace DesignLibrary
{
   [Flags]
   public enum Days : uint
   {
      None        = 0,
      Monday      = 1,
      Tuesday     = 2,
      Wednesday   = 4,
      Thursday    = 8,
      Friday      = 16,
      All         = Monday| Tuesday | Wednesday | Thursday | Friday
   }

   public enum Color :sbyte
   {
      None        = 0,
      Red         = 1,
      Orange      = 3,
      Yellow      = 4
   }
}

The following example fixes the previous violation by changing the underlying data type to Int32.

using System;

namespace Samples
{
    [Flags]
    public enum Days : int
    {
        None        = 0,
        Monday      = 1,
        Tuesday     = 2,
        Wednesday   = 4,
        Thursday    = 8,
        Friday      = 16,
        All         = Monday| Tuesday | Wednesday | Thursday | Friday
    }

    public enum Color : int
    {
        None        = 0,
        Red         = 1,
        Orange      = 3,
        Yellow      = 4
    }
}
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