Error: Sequence contains no matching element in C# Asp.Net
Dung Do Tien
May 17 2022
363
I have created a service in .Net 6 that helps get a list of data and transfer it to the MySQL database. I wrote a function help insert data like this:
public async Task<int> MultipleInserBooks(List<BooksInfoEntities> books)
{
try
{
if (books == null || !books.Any()) return 0;
List<BooksInfoEntities> newBooks = new List<BooksInfoEntities>();
// check duplicate books
foreach (var book in books)
{
if (!string.IsNullOrEmpty(book.BookName))
{
var bookObj = newBooks.First(x => x.BookName.Trim().Equals(book.BookName));
if (bookObj == null)
{
newBooks.Add(book);
}
}
}
// Insert books and return
return updateBooks(newBooks);
}
}But when calling this method I got an exception threw System.InvalidOperationException: Sequence contains no matching element.
System.InvalidOperationException: Sequence contains no matching element
at BooksIndexer.Dal.BooksService.BooksServiceDal.<MultipleInserTokenSpam>d__3.MoveNext() in C:\Project\Books\Books.IO\BooksIndexer\BooksIndexer\BooksIndexer\BooksIndexer.Dal\BooksService\BooksServiceDal.cs:line 196
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at BooksIndexer.Bsl.BooksService.BooksServiceBsl.<Run>d__2.MoveNext() in C:\Project\Books\Books.IO\BooksIndexer\BooksIndexer\BooksIndexer\BooksIndexer.Bsl\BooksService\BooksServiceBsl.cs:line 44Round 2 is starting....
What is that mean?
I used VS2022 and .Net 6.0, Window 11.
Thanks in advance.
Have 1 answer(s) found.
-
Z0
Zvonimir Markov May 17 2022
I got same the error as you. See this line of code below:
var bookObj = newBooks.First(x => x.BookName.Trim().Equals(book.BookName));You got this issue because you are using
First()LinQ function.Solution: Change
First()toFirstOrDefault()function. And your issue will be solved.
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