如何在字典C＃中替换int值

Question

I am wondering how I could replace int values in a dictionary in C#. The values would look something like this.

• 25,12
• 24,35
• 12,34
• 34,12

I was wondering how I could only replace one line. For example if I wanted to replace the first line with a new value of 12,12. And it wouldn't replace any of the other '12' values in the dictionary.

Answer 1

A Dictionary<TInt, TValue> makes use of what are known as indexers. In this case, these are used to access elements in the dictionary by key, hence:

dict[25] would return 12 .

Now, according to what you want to do is to have a key of 12 and a value of 12 . Unfortunately, you cannot replace entries in a dictionary by key, so what you must do is:

if(dict.ContainsKey(25))
{
    dict.Remove(25);
}
if(!dict.ContainsKey(12))
{
    dict.Add(12, 12);
}

Note: In the values you supplied, there is already a key-value pair with 12 as its key, so you would not be allowed to add 12,12 to the dictionary as if(!dict.ContainsKey(12)) would return false.

Answer 2

You cannot replace the first line with 12, 12 because there is another key value pair with 12 as it's key. And you cannot have duplicate keys in a dictionary.

Anyway you may do such things like this:

Dictionary<int, int> myDictionary = new Dictionary<int, int>();
myDictionary.Add(25, 12);
myDictionary.Add(24, 35);

//remove the old item
myDictionary.Remove(25);

//add the new item
myDictionary.Add(12, 12);

EDIT: if you are going to save some x,y positions I would suggest you creating a class named Point and use a List<Point> . Here is the code:

class Point
{
    public double X {get; set;}
    public double Y {get; set;}

    public Point(double x, double y)
    {
        this.X = x;
        this.Y = y;
    }
}

Then:

List<Point> myList =new List<Point>();
myList.Add(new Point(25, 13));

Answer 3

In Dictionaries, the keys must be unique.

In case the key need not be unique, you could use a List<Tuple<int, int>> or List<CustomClass> with CustomClass containing two integer fields. Then you may add or replace the way you want.