Enum.IsDefined、Enum.Parse和Enum.GetName。 这3个方法的用法是什么 有什么作用 特别是里面的参数 最好举例说明 谢谢

public static bool IsDefined (
    Type enumType,
    Object value
)
public static Object Parse (
    Type enumType,
    string value
)
Converts the string representation of the name or numeric value of one or more enumerated constants to an equivalent enumerated object.
public static Object Parse (
    Type enumType,
    string value,
    bool ignoreCase
)

Converts the string representation of the name or numeric value of one or more enumerated constants to an equivalent enumerated object. A parameter specifies whether the operation is case-sensitive.
public static string[] GetNames (
    Type enumType
)