System.InvalidOperationException: Sequence contains no elements

.NET · updated 2026-11-13

Thrown by LINQ's First, Last, Single, Min, Max and Average when the sequence is empty (and by Entity Framework's FirstAsync and SingleAsync when the query returns no rows). Single also throws "Sequence contains more than one element" when there are two or more.

Unhandled exception. System.InvalidOperationException: Sequence contains no elements
   at System.Linq.ThrowHelper.ThrowNoElementsException()
   at System.Linq.Enumerable.First[TSource](IEnumerable`1 source)
   at Program.<Main>$(String[] args) in /app/Program.cs:line 2

Quick fix

Find the First/Single/Last/Max call in the first frame from your code. If an empty result is possible, switch to FirstOrDefault (or SingleOrDefault) and handle null, or check Any() first. If it should never be empty, the bug is upstream: the filter, the data or a missing seed row, so fail with a message that names what was missing.

1. Skip the System.Linq frames: the first frame from your code is the call that hit an empty sequence.
2. Decide whether empty is a normal result (no orders yet, no match for a filter).
3. Normal: use FirstOrDefault/SingleOrDefault and handle null, or DefaultIfEmpty for Max/Min.
4. Not normal: check the filter and the data, and throw a clear exception (or return 404) that names the missing record.

var latest = orders
    .Where(o => o.Paid)
    .OrderByDescending(o => o.At)
    .FirstOrDefault();

if (latest is null)
    return Results.NotFound("no paid orders yet");

// Max on a possibly empty sequence
var newest = orders.Select(o => (DateTime?)o.At).Max(); // null when empty

Read https://runheed.com/errors/dotnet-sequence-contains-no-elements.md and fix this error in this project.

Why it happens

Other fixes

• In Entity Framework, use FirstOrDefaultAsync and return 404 for a missing record from an API.
• Add a unique index where you use Single, so duplicates fail on insert instead of on read.

Same error, other wording

• System.InvalidOperationException: Sequence contains more than one element
• System.InvalidOperationException: Sequence contains no matching element

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References: .NET API: Enumerable.First, .NET API: Enumerable.FirstOrDefault

Spotted a mistake? Email hello@greatwork.company. About Runheed.