Linq code to select one item

Question

I find myself writing a lot of code like this to select one item that matches   var item    from x in Items where x Id    123 select x  First      Is there a cleaner way of doing it or is this as concise as I m going to get   EDIT  Should have said  Cleaner way using linq syntax   I was already aware of the lambda syntax and it s starting to look like this is actually the only way  I did get some useful info though  so thanks to everyone who replied

User · Answer

I ll tell you what worked for me   int id   int Parse insertItem OwnerTableView DataKeyValues insertItem ItemIndex   id usuario   ToString      var query   user First x   gt  x id usuario    id   tbUsername Text   query username  tbEmail Text   query email  tbPassword Text   query password    My id is the row I want to query  in this case I got it from a radGrid  then I used it to query  but this query returns a row  then you can assign the values you got from the query to textbox  or anything  I had to assign those to textbox

User · Answer

Depends how much you like the linq query syntax  you can use the extension methods directly like   var item   Items First i   gt  i Id    123     And if you don t want to throw an error if the list is empty  use FirstOrDefault which returns the default value for the element type  null for reference types    var item   Items FirstOrDefault i   gt  i Id    123    if  item    null           found it     Single   and SingleOrDefault   can also be used  but if you are reading from a database or something that already guarantees uniqueness I wouldn t bother as it has to scan the list to see if there s any duplicates and throws   First   and FirstOrDefault   stop on the first match  so they are more efficient   Of the First   and Single   family  here s where they throw    First   - throws if empty not found  does not throw if duplicate FirstOrDefault   - returns default if empty not found  does not throw if duplicate Single   - throws if empty not found  throws if duplicate exists SingleOrDefault   - returns default if empty not found  throws if duplicate exists

User · Answer

That can better be condensed down to this   var item   Items First x   gt  x Id    123    Your query is currently collecting all results  and there may be more than one  within the enumerable and then taking the first one from that set  doing more work than necessary   Single SingleOrDefault are worthwhile  but only if you want to iterate through the entire collection and verify that the match is unique in addition to selecting that match  First FirstOrDefault will just take the first match and leave  regardless of how many duplicates actually exist

User · Answer

These are the preferred methods   var item   Items SingleOrDefault x   gt  x Id    123     Or  var item   Items Single x   gt  x Id    123

User · Answer

Just to make someone s life easier  the linq query with lambda expression    from x in Items where x Id    123 select x  FirstOrDefault      does result in an SQL query with a  select top  1  in it

User · Answer

FirstOrDefault or SingleOrDefault might be useful  depending on your scenario  and whether you want to handle there being zero or more than one matches   FirstOrDefault  Returns the first element of a sequence  or a default value if no element is found  SingleOrDefault  Returns the only element of a sequence  or a default value if the sequence is empty  this method throws an exception if there is more than one element in the sequence  I don t know how this works in a linq  from  query but in lambda syntax it looks like this  var item1   Items FirstOrDefault x   gt  x Id    123   var item2   Items SingleOrDefault x   gt  x Id    123

User · Answer

You could use the extension method syntax   var item   Items Select x   gt  x Id    123  FirstOrDefault      Other than that  I m not sure how much more concise you can get  without maybe writing your own specialized  First  and  FirstOrDefault  extension methods

[c#] Linq code to select one item

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