Select single item from a list

Question

Using LINQ what is the best way to select a single item from a list if the item may not exists in the list   I have come up with two solutions  neither of which I like   I use a where clause to select the list of items  which I know will only be one   I can then check the count and make a Single call on this list if count is one  the other choice is to use a foreach and just break after getting the item   Neither of these seem like a good approach  is there a better way

User · Answer

Just to complete the answer  If you are using the LINQ syntax  you can just wrap it since it returns an IEnumerable    from int x in intList  where x  gt  5  select x   2  FirstOrDefault

User · Answer

You can use IEnumerable First   or IEnumerable FirstOrDefault     The difference is that First   will throw if no element is found  or if no element matches the conditions  if you use the conditions    FirstOrDefault   will return default T   null if it s a reference type

User · Answer

just saw this now  if you are working with a list of object you can try this   public class user       public string username   get  set        public string password   get  set         List lt user gt  userlist   new List lt user gt              userlist Add new user   username    macbruno   password    1234              userlist Add new user   username    james   password    5678              string myusername    james           string mypassword    23432      user theUser   userlist Find              delegate  user thisuser                                return thisuser username   myusername  amp  amp  thisuser password    mypassword                                            if  theUser    null                               Dosomething                              else                               DoSomethingElse

User · Answer

Use the FirstOrDefault selector   var list   new int     1  2  3  4  5  6  7  8  9  10     var firstEven   list FirstOrDefault n   gt  n   2    0    if  firstEven    0      Console WriteLine  no even number    else      Console WriteLine  first even number is  0    firstEven     Just pass in a predicate to the First or FirstOrDefault method and it ll happily go round  the list and picks the first match for you   If there isn t a match  FirstOrDefault will returns the default value of whatever datatype the list items is   Hope this helps  -

User · Answer

SingleOrDefault   is what you need  cheers

User · Answer

There are two easy ways  depending on if you want to deal with exceptions or get a default value   You can use the First lt T gt    or the FirstOrDefault lt T gt    extension method to get the first result or default T    var list   new List lt int gt    1  2  4    var result   list Where i   gt  i    3  First       throws InvalidOperationException var result   list Where i   gt  i    3  FirstOrDefault         0

User · Answer

List lt string gt  items   new List lt string gt      items Find p   gt  p     blah      or  items Find p   gt  p Contains  b       but this allows you to define what you are looking for via a match predicate     I guess if you are talking linqToSql then   example looking for Account     DataContext dc   new DataContext     Account item   dc Accounts FirstOrDefault p   gt  p id    5     If you need to make sure that there is only 1 item  throws exception when more than 1   DataContext dc   new DataContext     Account item   dc Accounts SingleOrDefault p   gt  p id    5

User · Answer

Maybe I m missing something here  but usually calling  SingleOrDefault   is the way to go to return either the single element in the list  or a default value  null for reference or nullable types  if the list is empty   It generates an exception if the list contains more than one element   Use FirstOrDefault   to cover the case where you could have more than one

[c#] Select single item from a list

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