Question

我在ASP.net中有一些会话如下。在文件Test.aspx.cs中有一些会话

 public class MySession
    {
        // private constructor
        private MySession()
        {
            value_group = "Group";
            //value_id = "Id";
            //value_region = "Region";
        }
        // Gets the current session.
        public static MySession Current
        {
            get
            {
                MySession session =(MySession)HttpContext.Current.Session["Group"];
                if (session == null)
                {
                    session = new MySession();
                    HttpContext.Current.Session["Group"] = session;
                }
                return session;
            }
        }
        // **** add your session properties here, e.g like this:
        public string value_group { get; set; }
        //public string value_id { get; set; }
        //public string value_region { get; set; }
    }

然后我创建了一些课程，我想获得会话的价值。

首先，我创建了一个MySession.cs类

 string value_group = MySession.Current.value_group.ToString();
                //string value_id = MySession.Current.value_id.ToString();
                //string value_region = MySession.Current.value_region.ToString();

其次，我创建了类Test.cs，我希望获得会话值

Object reference not set to an instance of an object

但是它得到了错误

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--use IEEE.NUMERIC_STD.ALL;

-- Uncomment the following library declaration if instantiating
-- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity ALU_8_bit is
    Port ( A : in  STD_LOGIC_VECTOR (3 downto 0);
           B : in  STD_LOGIC_VECTOR (3 downto 0);
           CTRL : in  STD_LOGIC_VECTOR (2 downto 0);
           Y : out  STD_LOGIC_VECTOR (3 downto 0);
              OFL: out STD_LOGIC;
              COUT: out STD_LOGIC
              );
end ALU_8_bit;



architecture Behavioral of ALU_8_bit is

signal result: std_logic_vector(3 downto 0);


begin

process(A,B,CTRL) begin
    if (CTRL ="000") then
        result <= A; 
    elsif (CTRL = "001") then
        result <= A + B; 
    elsif (CTRL = "010") then
        result <= A - B;
    elsif (CTRL = "011") then
        result <= NOT A + 1;
    elsif (CTRL = "100") then
        result <= NOT A; 
    elsif (CTRL = "101") then
        result <= A AND B;
    elsif (CTRL = "110") then 
        result <= A OR B;  
    else --(CTRL = "111") then
        result <= A XOR B;
    end if;
end process;

Y <= result;

--process (A,B,result,cout)
--begin
--  if  ((A(3) = '1') and (B(3) ='1') and (result(3) = '0')) then Cout <= '1';
--  elsif ((A(3) = '1') and (B(3) = '0') and (result(3) = '0')) then Cout <= '1';
--  elsif ((A(3) = '0') and (B(3) = '1') and (result(3) = '0')) then Cout <= '1';
--  else Cout <= '0';
--  end if;
--end process;

process(result,CTRL)
begin 
    if (CTRL = "001") then
        --Y <= result;
        COUT <=  A(3) and B(3); --result(3);
        OFL <= result(3) xor (B(2) and A(2));
    else 
        OFL <= '0';
        COUT <= '0';
    end if;
end process;

end Behavioral;

谢谢你们。

Answer 1

正如您在评论中所说，您需要一个适用于Session的包装类。

以下是如何轻松实现它的方法。我试着遵循你最多写的代码：

public class MySession
{
    private const string GroupKey = "Group";
    private const string RegionKey = "Region";
    private const string IDKey = "Id";

    private static MySession _session;  
    public static MySession Current
    {
        get
        {
            return _session ?? (_session = new MySession());
        }
    }

    public string Group 
    { 
        get
        {
            return HttpContext.Current.Session[GroupKey] as string;
        }
        set
        {
            HttpContext.Current.Session[GroupKey] = value;
        }
    }

    public string Region
    {
        get
        {
            return HttpContext.Current.Session[RegionKey] as string;
        }
        set
        {
            HttpContext.Current.Session[RegionKey] = value;
        }
    }

    public string ID
    {
        get
        {
            return HttpContext.Current.Session[IDKey] as string;
        }
        set
        {
            HttpContext.Current.Session[IDKey] = value;
        }
    }
}

但是，您可能不需要它。您只使用一个当前HttpContext.Current.Session。这些值会动态更改，我猜想，您想获取实际数据。因此，您的包装类可以是静态包装类。

public static class SessionWrapper
{
    private const string GroupKey = "Group";
    private const string RegionKey = "Region";
    private const string IDKey = "Id";

    public static string Group 
    { 
        get
        {
            return HttpContext.Current.Session[GroupKey] as string;
        }
        set
        {
            HttpContext.Current.Session[GroupKey] = value;
        }
    }

    public static string Region
    {
        get
        {
            return HttpContext.Current.Session[RegionKey] as string;
        }
        set
        {
            HttpContext.Current.Session[RegionKey] = value;
        }
    }

    public static string ID
    {
        get
        {
            return HttpContext.Current.Session[IDKey] as string;
        }
        set
        {
            HttpContext.Current.Session[IDKey] = value;
        }
    }
}

此外，它不正确。我不会这样做，因为你要为每个会话属性描述一个键，getter和setter。如果您在会话中添加新属性（例如，＆＃39;语言＆＃39;），您将需要显着更改违反OCP原则的MySession类。

如何在课堂上获得会话价值？

1 个答案: