c# - how can i update SQL table logic -

i have table structured as,

table 3  fruit id -  foreign key  (primary key of table 1) crate id -  foreign key  (primary key of table 2) 

now need execute query will,

update crate id of fruit id if fruit id is in table, , if not insert record in table 3 new record.

this got in code right now,

private void relatefuirtwithcrates(list<string> selectedfruitids, int selectedcrateid) {     string insertstatement = "insert fruit_crate(fruitid, crateid) values " +         "(@fruitid, @crateid);";  ?? don't think if it's right query          using (sqlconnection connection = new sqlconnection(connectionstring()))         using (sqlcommand cmd = new sqlcommand(insertstatement, connection))         {             connection.open();             cmd.parameters.add(new sqlparameter("@fruitid", ????? not sure goes in here));             cmd.parameters.add(new sqlparameter("@crateid",selectedcrateid));         } 

you can "upsert" merge syntax in sql server:

merge [sometable] target using (select @fruitid, @crateid) source (fruitid, crateid) on (target.fruitid = source.fruitid) when matched      update set crateid = source.crateid when not matched        insert (fruitid, crateid)     values (source.fruitid, source.crateid); 

otherwise, can use like:

update [sometable] set crateid = @crateid fruitid = @fruitid if @@rowcount = 0     insert [sometable] (fruitid, crateid) values (@fruitid, @crateid)