Given a list:
private List<KeyValuePair<string, string>> KV_List = new List<KeyValuePair<string, string>>();
void initList()
{
KV_List.Add(new KeyValuePair<string, string>("qwer", "asdf"));
KV_List.Add(new KeyValuePair<string, string>("qwer", "ghjk"));
KV_List.Add(new KeyValuePair<string, string>("zxcv", "asdf"));
KV_List.Add(new KeyValuePair<string, string>("hjkl", "uiop"));
}
(NOTE: there are multiple values for the key "qwer" and multiple keys for the value "asdf".)
1) Is there a better way to return a list of all keys than just doing a foreach on the KeyValuePair List?
2) Similarly, is there a better way to return a list of all values for a given key than using a foreach?
3) And then, how about returning a list of keys for a given value?
Thanks...
// #1: get all keys (remove Distinct() if you don't want it)
List<string> allKeys = (from kvp in KV_List select kvp.Key).Distinct().ToList();
// allKeys = { "qwer", "zxcv", "hjkl" }
// #2: get values for a key
string key = "qwer";
List<string> values = (from kvp in KV_List where kvp.Key == key select kvp.Value).ToList();
// values = { "asdf", "ghjk" }
// #3: get keys for a value
string value = "asdf";
List<string> keys = (from kvp in KV_List where kvp.Value == value select kvp.Key).ToList();
// keys = { "qwer", "zxcv" }
It sounds like you would benefit from using something like:
Dictionary<string, List<string>> kvlist;
kvlist["qwer"] = new List<string>();
kvlist["qwer"].Add("value1");
kvlist["qwer"].Add("value2");
foreach(var value in kvlist["qwer"]) {
// do something
}
It would be relatively easy to create a basic mutli-value dictionary class using a Dictionary and List.
This blog post talks more about Microsoft's MultiDictionary type available via NuGet.
You can use NameValueCollection from System.Collection.Specialized namespace:
NameValueCollection KV_List = new NameValueCollection();
KV_List.Add("qwer", "asdf");
KV_List.Add("qwer", "ghjk");
KV_List.Add("zxcv", "asdf");
KV_List.Add("hjkl", "uiop");
Example of use:
string singleValue = KV_List["zxcv"]; // returns "asdf"
string[] values = KV_List.GetValues("qwer"); // returns "asdf, "ghjk"
string[] allKeys = KV_List.AllKeys;
string[] allValues = KV_List.AllKeys;