C＃字典，如何获取特定值

Question

I have created a dictionary, and I want the user to write the city ( kommune) and then get the value (procent) displayed in a text box called txtKommuneresultalt

I am new to C#, so I hope someone can help me

I have tried searching for days now, nothing works.I am using Windowsforms, and have the buttonHandler ready

this so far is my code:

Dictionary<double, string> dictionary = new Dictionary<double, string>();
double procent = Convert.ToDouble(txtKommuneresultat.Text);
string kommune = txtKommuneInput.Text;


dictionary.Add(11.44, "Faxe");
dictionary.Add(4.29, "Greve");
dictionary.Add(7.11, "Gulborgsund");
dictionary.Add(7.86, " Holbæk");
dictionary.Add(5.67, "Kalundborg");
dictionary.Add(4.99, "Køge");
dictionary.Add(7.28, "Lejre");
dictionary.Add(2.67, "Lolland");
dictionary.Add(4.07, "Næstved");
dictionary.Add(1.21, "Odsherred");
dictionary.Add(5.02, "Ringsted");
dictionary.Add(13.23, "Slagelse");
dictionary.Add(20.75, "Solrød");
dictionary.Add(1.81, "Sorø");
dictionary.Add(5.50, "Stevns");
dictionary.Add(1.29, "Vordingborg");

txtKommuneresultat.Show();

Answer 1

The first type in a dictionary is the key and the second is the value . A dictionary allow you to look up a value based on that value's key .

Currently, you have a double as the first type (the key) and a string as the second type (the value). This would allow you to look up a string value by using a double value as a key.

But wait. Your doubles are representing a percentage, while your strings represent a city name. You want to look up a percentage, based on the city name. So the string should be the key in your dictionary, not the double.

Dictionary<string, double> dictionary = new Dictionary<string, double>();

This allow you to get a specific double value by providing the right string:

var percentage = dictionary["Gulborgsund"];

Since the lookup will be based on user input (which is usually unreliable), it would probably be best to use the TryGetValue method:

double percentage;
if (dictionary.TryGetValue(userInput, out percentage)) 
{
    // Use percentage
}
else 
{
    // Could not retrieve value
}

Answer 2

        string userInput = txtKommuneInput.Text;
        double procent;
        if (dictionary.TryGetValue(userInput, out procent))

            txtKommuneresultat.Text = procent.ToString();

Answer 3

How to fish:

Here is a good start for learning about Dictionary in C#:

https://msdn.microsoft.com/en-us/library/xfhwa508(v=vs.110).aspx#Anchor_8

Also, MSDN have a lot of useful resources there, please, feel free to explore.

How to do it (I think this will be specific to your case, I divided into two options, using city name as key or using percentage as key):

using System;
using System.Web.SessionState;
using System.Collections.Generic;

public class Program
{
    public static void Main()       
    {
        //Part 1: Using percentage as Key
        Dictionary<double, string> dictionary = new Dictionary<double, string>();

        dictionary.Add(11.44, "Faxe");          
        //(...)         
        dictionary.Add(1.29, "Vordingborg");

        //Here is Komune
        dictionary.Add(5.89, "Komune");

        if (dictionary.ContainsKey(5.89)){
            Console.WriteLine(String.Format("Found: {0}!", dictionary[5.89]));
        } else {
            Console.WriteLine("Not Found!");
        }



        //Part 2: Using the string as Key
        Dictionary<string,double> dictionaryStringPercent = new Dictionary<string,double>();

        dictionaryStringPercent.Add("Faxe",11.44);                  
        //(...)         
        dictionaryStringPercent.Add("Vordingborg",1.0);

        //Here is Komune
        dictionaryStringPercent.Add("Komune",5.89);

        if (dictionaryStringPercent.ContainsKey("Komune")){
            Console.WriteLine(String.Format("Found: {0}!", dictionaryStringPercent["Komune"]));
        } else {
            Console.WriteLine("Not Found!");
        }
    }
}