RCS1237: Use bit shift operator

Example

[Flags]
enum Foo // RCS1237
{
    None = 0,
    Alpha = 1,
    Beta = 2,
    Gamma = 4,
}

[Flags]
enum Foo
{
    None = 0,
    Alpha = 1,
    Beta = 1 << 1,
    Gamma = 1 << 2,
}