如何在C＃中向列表添加多个参数

Question

how to add string to...

List<int> mapIds = new List<int>();
mapIds.Add(36);
mapIds.Add(37);
mapIds.Add(39);

is a list with ints.....I would like to add strings to this list for each record...trying...

List<int, string> mapIds = new List<int, string>();
mapIds.Add(36, "hi");
mapIds.Add(37, "how");
mapIds.Add(39, "now");

tells me unkown type of variable?

Answer 1

List<T> is generic list of objects of type T .

If you want to have pairs <int, sting> in this list, it should be not List<int, string> , but List<Some_Type<int, string>> .

One of possible ways - is to use Tuple<T1, T2> as such a type.

Something like:

var mapIds = new List<Tuple<int, string>>();
mapIds.Add(new Tuple<int, string>("36", "hi"));

Or you can use Dictionary<TKey, TValue> instead of list, but in this case your integer values should be unique.

Answer 2

You can use Dictionary instead of List. For example:

Dictionary<int, string> dictionary = new Dictionary<int, string>();
dictionary.Add(36, "hi");

For more information: Dictionary Type on MSDN

Answer 3

You can just create a class:

class Custom
{
   public int myInt {get;set;}
   public string myString {get;set}
}

and then :

List<Custom> mapIds = new List<Custom>();
Custom c = new Custom();
c.myInt = 36;
c.myString="hi";
mapIds.Add(c);    
....
...

Answer 4

You can also use HashTable or SortedList as another option to Dictionary. Both classes are in the System.Collections namespace

Hashtable

A Hashtable enables you to store key/value pair of any type of object. The data is stored according to the hash code of the key and can be accessed by the key rather than the index. Example:

Hashtable myHashtable = new Hashtable(); 
myHashtable.Add(1, "one"); 
myHashtable.Add(2, "two"); 
myHashtable.Add(3, "three");

SortedList

A SortedList is a collection that contains key/value pairs, but is different to the HashTable because it can be referenced by the index and because it is sorted. Example:

SortedList sortedList = new System.Collections.SortedList();
sortedList.Add(3, "Third");
sortedList.Add(1, "First");
sortedList.Add(2, "Second");