1 public int Id { get; set; }
2 public string Name { get; set; }

public string Name { get; set; } = "summit";
public int Age { get; set; } = 22;
public DateTime BirthDay { get; set; } = DateTime.Now.AddYears(-20);
public IList<int> AgeList
{
  get;
  set;
} = new List<int> { 10, 20, 30, 40, 50 };

Math.Abs(20d);

using static System.Math;
 
private void Form1_Load(object sender, EventArgs e)
  {
   Abs(20d);
  }

if (student!=null)
{
 string fullName = student.FullName;
}
else
{
 //……
}

string fullName = student?.FullName; //如果student為空則返回Null,不為空則返回.FullNaem,注意！得到的結(jié)果一定是要支持null

string str = $"{firstName}和{lastName}"

try
{
 
}
catch(Exception e) when(e.Message.Contains("異常過濾，把符合條件的異常捕獲")
{
}

Console.WriteLine(nameof(System.Collections.Generic)); // output: Generic
Console.WriteLine(nameof(List<int>)); // output: List

Dictionary<int, string> messages = new Dictionary<int, string>
    {
     { 404, "Page not Found"},
     { 302, "Page moved, but left a forwarding address."},
     { 500, "The web server can't come out to play today."}
    };

Dictionary<int, string> webErrors = new Dictionary<int, string>
    {
     [404] = "Page not Found",
     [302] = "Page moved, but left a forwarding address.",
     [500] = "The web server can't come out to play today."
    };

public string NameFormat => string.Format("姓名: {0}", "summit");
public void Print() => Console.WriteLine(Name);