如何将检查键添加到hastable及其对应的值中 [英] How do check key already added to a hastable and their corresponding values

问题描述

public static DateTime LoggedOn = DateTime.Now;

Hashtable ht = new Hashtable();

hash.Add("Hello", LoggedOn);  // output like "Hello", 18.11.2016 09:52:07 
hash.Add("Hello", LoggedOn);   // output like "Hello", 18.11.2016 09:52:27 
hash.Add("Hello", LoggedOn);    // output like "Hello", 18.11.2016 09:52:55

bool htexists = ht.ContainsKey("Hello");
bool valueexists = ht.ContainsValue(LoggedOn);

if (htexists && valueexists)
{
//if it is first entry allow it 
//my first question it returns always true as i have addaded key and value to my ht but i want to check when it is added more than one time of not if first entry OK

// my second ?  how to check then correspondend value in my case with time  
//if same message say hello is added within few minutes then cancel of say only allowes to add same message during interval of 1 hour or 1 day
}

What I have tried:

First i would like to check if value already exists or not i have done something like this

推荐答案

只需检查键和值存在：

Just check if key and value exists:

if(hash.ContainsKey("c") && hash["c"] == "3") { }

您也可以创建扩展方法如下：

You can also create extension method like below:

public partial class Page2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Hashtable hashtable = new Hashtable();
        hashtable.AddIfNotExists("Time1", Convert.ToDateTime("11/18/2016 3:43:33 PM"));
        hashtable.AddIfNotExists("Time2", Convert.ToDateTime("11/18/2016 3:43:34 PM"));
        hashtable.AddIfNotExists("Time3", Convert.ToDateTime("11/18/2016 3:43:33 PM"));
        hashtable.AddIfNotExists("Time4", Convert.ToDateTime("11/18/2016 3:43:35 PM"));   
    }
}

public static class Extension
{
    public static void AddIfNotExists(this Hashtable hash, string key1, DateTime value2)
    {
        if (hash.ContainsKey(key1) == false && Convert.ToDateTime((hash[key1])) != value2)
        {            
            hash.Add(key1, value2);
        }
    }
}

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