Get first element from a dictionary

Question

I have the following declaration   Dictionary lt string  Dictionary lt string  string gt  gt  like   new Dictionary lt string  Dictionary lt string  string gt  gt       I need to get the first element out  but do not know the key or value  What s the best way to do this

User · Answer

ill find easy way to find first element in Dictionary      Dictionary lt string  Dictionary lt string  string gt  gt  like     newDictionary lt string Dictionary lt string  string gt  gt       foreach KeyValuePair lt string  Dictionary lt string  string gt  gt   element in like        Console WriteLine  element Key      or do something    break

User · Answer

convert to Array  var array   like ToArray    var first   array 0

User · Answer

Note that to call First here is actually to call a Linq extension of IEnumerable  which is implemented by Dictionary lt TKey TValue gt    But for a Dictionary   first  doesn t have a defined meaning   According to this answer  the last item added ends up being the  First   in other words  it behaves like a Stack   but that is implementation specific  it s not the guaranteed behavior   In other words  to assume you re going to get any defined item by calling First would be to beg for trouble -- using it should be treated as akin to getting a random item from the Dictionary  as noted by Bobson below   However  sometimes this is useful  as you just need any item from the Dictionary     Just use the Linq First     var first   like First    string key   first Key  Dictionary lt string string gt  val   first Value    Note that using First on a dictionary gives you a KeyValuePair  in this case KeyValuePair lt string  Dictionary lt string string gt  gt      Note also that you could derive a specific meaning from the use of First by combining it with the Linq OrderBy   var first   like OrderBy kvp   gt  kvp Key  First

User · Answer

For anyone coming to this that wants a linq-less way to get an element from a dictionary  var d   new Dictionary lt string  string gt     d Add  a    b    var e   d GetEnumerator    e MoveNext    var anElement   e Current     anElement e Current is a KeyValuePair lt string string gt     where Key    a   Value    b    I m not sure if this is implementation specific  but if your Dictionary doesn t have any elements  Current will contain a KeyValuePair lt string  string gt  where both the key and value are null    I looked at the logic behind linq s First method to come up with this  and tested it via LinqPad 4

User · Answer

Dictionary does not define order of items  If you just need an item use Keys or Values properties of dictionary to pick one

User · Answer

Though you can use First    Dictionaries do not have order per se  Please use OrderedDictionary instead  And then you can do FirstOrDefault  This way it will be meaningful

User · Answer

EDIT   Use an OrderedDictionary   It s better to use FirstOrDefault   to retrieve the first value   Ex   var firstElement   like FirstOrDefault    string firstElementKey   firstElement Key  Dictinary lt string string gt  firstElementValue   firstElement Value

User · Answer

Dictionary lt string  Dictionary lt string  string gt  gt  like   new Dictionary lt string  Dictionary lt string  string gt  gt     Dictionary lt string  string gt  first   like Values First

[c#] Get first element from a dictionary

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