无法从列表中检索数据<keyvaluepair>

Question

List<KeyValuePair<String, String> myList = new List<KeyValuePair<String, String>>();

myList.Add(new KeyValuePair<String, SelectList>("theKey", "FIND THIS!"));

How can I retrieve "FIND THIS!" from myList knowing only theKey ? This attempt is not working.

String find = myList.Where(m => m.Key == "theKey");

Coming from other languages, I've always had the possibility to search in big associative arrays and retrieve values like this: array[key] = value;

How can I do this in C#?

Answer 1

Instead of List<KeyValuePair> , use Dictionary<string, SelectList> and then you can access it like :

array[key] = value;

You can use Dictionary like:

Dictionary<String, SelectList> dictionary= new Dictionary<String, SelectList>();
dictionary.Add("theKey", "FIND THIS!");

Console.WriteLine(dictionary["theKey"]);

Answer 2

You are probably looking for the Dictionary<TKey, TValue> :

Dictionary<string, string> myDict = new Dictionary<string, string>();
myDict.Add("theKey", "FIND THIS!");

now you can find the value via the key:

string value = myDict["theKey"];

You can change the value in this way:

myDict["theKey"] = "new value";  // works even if the key doesn't exist, then it will be added

Note that the keys must be unique.

Answer 3

How about Dictionary ?

IDictionary<String, String> foo = new Dictionary<String, String>();
foo.Add("hello","world");

now you can use []

foo["Hello"];

however with C#

string value;

if(foo.TryGetValue("Hello" , out value)){
   // now you have value
}

is much more preferable and safer.

Answer 4

As mentioned in other answers you should use a Dictionary for this.

However, the reason your line String find = myList.Where(m => m.Key == "theKey"); is not working is that myList.Where(m => m.Key == "theKey"); will return a KeyValuePair . If you just want the value you could try:

String find = myList.Where(m => m.Key == "theKey").Single().Value;

or if you need to check for nulls then maybe:

var findKeyValue = myList.Where(m => m.Key == "theKey").SingleOrDefault();
if(findKeyValue != null)
{
    var find = findKeyValue.Value;
}

You can also use the following snippet (in which case you'll either have the value or null)

var find = myList.Where(m => m.Key == "theKey").Select(kvp => kvp.Value).SingleOrDefault();