C#中变量、常量、枚举、预处理器指令知多少

public class VariableDefine
  {
    private static uint variableUInt;
    public static uint VariableUInt { get => variableUInt; set => variableUInt = value; }
    string VariableStr;
    public VariableDefine(string version)
    {
      VariableStr = version;
    }

    public static void Fun()
    {  
      Console.WriteLine(variableUInt);
    }

    /// <summary>
    /// 变量类型
    /// </summary>
    /// <param name="intArray">intArray[0]数组元素</param>
    /// <param name="a">数值参数</param>
    /// <param name="b">引用类型</param>
    /// <param name="c">输出参数</param>
    public void Fun(int[] intArray, int a, ref int b, out int c)
    {
      //局部变量i
      var i = 0;
      c = i;
    }
  }

public sealed class ReadOnlyModel
  {
    public readonly List<Company> ListCompany;
    public ReadOnlyModel(string companyInfoPath)
    {
      XElement companys = XElement.Load(companyInfoPath);
      var elements = from e in companys.Elements("company")
              where e.Element("name").Value.Equals("C#")
              select e;
      ListCompany = GetListCompany(elements);
    }

    /// <summary>
    /// 解析xml文档
    /// </summary>
    /// <param name="elements"></param>
    /// <returns></returns>
    private List<Company> GetListCompany(IEnumerable<XElement>elements)
    {
      var listCompany = new List<Company>();
      foreach (var element in elements)
      {
        var companyModel = new Company()
        {
          CompanyName = element.Element("name").Value,
          CompanyEmail = element.Element("email").Value
        };
        listCompany.Add(companyModel);
      }
      return listCompany;
    }
  }

class Program
  {
    static void Main(string[] args)
    {
      //ReadOnlyModel readOnlyCompany = new ReadOnlyModel(@"D:\GitHubProject\C#AdvancedProgramming\VariableDefine\VariableDefine\bin\Debug\Test-Parking-SN.xml"); //C:\Program Files(x86)\FPOnline
      //foreach (var company in readOnlyCompany.ListCompany)
      //{
      //  Console.WriteLine("company name is {0} company email is {1}", company.CompanyName, company.CompanyEmail);
      //}
      //Console.WriteLine("company name is {0} company email is {1}", ConstClass.CompanyName, ConstClass.CompanyEmail);
      MemberLevel superMember = MemberLevel.SuperMember;
      Console.WriteLine(superMember.GetDescriptionEnum());
      Console.ReadKey();
    }
  }

  public enum MemberLevel
  {
    [Description("超级会员")]
    SuperMember=1,
    [Description("一般会员")]
    Member=2,
    [Description("普通用户")]
    GeneralUser=3
  }

  public static class EnumExtension
  {
    public static string GetDescriptionEnum(this Enum enumValue)
    {
      DescriptionAttribute attr = null;
      var enumType = enumValue.GetType();
      string name = Enum.GetName(enumType, enumValue);
      if (name != null)
      {
        FieldInfo fieldInfo = enumType.GetField(name);
        if (fieldInfo != null)
          attr = Attribute.GetCustomAttribute(fieldInfo, typeof(DescriptionAttribute), false) as DescriptionAttribute;
      }
      if (attr != null && !string.IsNullOrEmpty(attr.Description))
        return attr.Description;
      else return string.Empty;
    }
  }