Sequence contains more than one element

Question

I m having some issues with grabbing a list of type  RhsTruck  through Linq and getting them to display    RhsTruck just has properites Make  Model  Serial etc    RhsCustomer has properties CustomerName  CustomerAddress  etc     I keep getting the error  Sequence contains more than one element   Any ideas  Am I approaching this the wrong way   public RhsCustomer GetCustomer string customerNumber        using  RhsEbsDataContext context   new RhsEbsDataContext                   RhsCustomer rc    from x in context custmasts                           where x kcustnum    customerNumber                           select new RhsCustomer                                                         CustomerName   x custname                              CustomerAddress   x custadd          x custcity                             CustomerPhone   x custphone                              CustomerFax   x custfax                            SingleOrDefault            return rc           public List lt RhsTruck gt  GetEquipmentOwned RhsCustomer cust        using  RhsEbsDataContext context   new RhsEbsDataContext                  var trucks    from m in context mkpops                       join c in context custmasts                         on m kcustnum equals c kcustnum                       where m kcustnum    cust CustomerNumber                       select new RhsTruck                                               Make   m kmfg                          Model   m kmodel                          Serial   m kserialnum                          EquipID   m kserialno1                          IsRental   false                        ToList            return trucks           protected void Page Load object sender  EventArgs e        string testCustNum   Page Request QueryString  custnum   ToString         RhsCustomerRepository rcrep   new RhsCustomerRepository        RhsCustomer rc   rcrep GetCustomer testCustNum       List lt RhsTruck gt  trucks   rcrep GetEquipmentOwned rc           I want to display the List into a Gridview w auto-generated columns     GridViewTrucks DataSource   trucks      GridViewTrucks DataBind

User · Answer

SingleOrDefault method throws an Exception if there is more than one element in the sequence    Apparently  your query in GetCustomer is finding more than one match  So you will either need to refine your query or  most likely  check your data to see why you re getting multiple results for a given customer number

User · Answer

As  Mehmet is pointing out  if your result is returning more then 1 elerment then you need to look into you  data as i suspect that its not by design that you have customers sharing a customernumber    But to the point i wanted to give you a quick overview     success on 0 or 1 in the list  returns dafault   of whats in the list if 0 list SingleOrDefault      success on 1 and only 1 in the list list Single       success on 0-n  returns first element in the list or default   if 0  list FirstOrDefault      success 1-n  returns the first element in the list list First       success on 0-n  returns first element in the list or default   if 0  list LastOrDefault      success 1-n  returns the last element in the list list Last      for more Linq expressions have a look at System Linq Expressions

User · Answer

The problem is that you are using SingleOrDefault   This method will only succeed when the collections contains exactly 0 or 1 element   I believe you are looking for FirstOrDefault which will succeed no matter how many elements are in the collection

User · Answer

Use FirstOrDefault insted of SingleOrDefault     SingleOrDefault returns a SINGLE element or null if no element is found  If 2 elements are found in your Enumerable then it throws the exception you are seeing  FirstOrDefault returns the FIRST element it finds or null if no element is found  so if there are 2 elements that match your predicate the second one is ignored     public int GetPackage int id int emp                            int getpackages Convert ToInt32 EmployerSubscriptionPackage GetAllData   Where x      gt  x SubscriptionPackageID    enter code here  id  amp  amp  x EmployerID  emp   FirstOrDefault   ID                  return getpackages                 1  var EmployerId   Convert ToInt32 Session  EmployerId                    var getpackage   GetPackage employerSubscription ID  EmployerId

User · Answer

FYI you can also get this error if EF Migrations tries to run with no Db configured  for example in a Test Project   Chased this for hours before I figured out that it was erroring on a query  but  not because of the query but because it was when Migrations kicked in to try to create the Db

[c#] Sequence contains more than one element

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