dotnet/efcore · error · InvalidOperationException

Unable to execute a 'ReadItem' query since the 'id' value…

Error message

Unable to execute a 'ReadItem' query since the 'id' value is missing and cannot be generated.

What it means

During MoveNextAsync of a ReadItem enumeration, the enumerator calls TryGetResourceId; if id generation produces no usable resource id it throws InvalidOperationException ResourceIdMissing. Distinct from InvalidResourceId: this covers the path where the id cannot even be assembled for the request.

Solutions

Verify the entity's primary key is fully configured and all key properties are populated before querying.
Ensure the key properties used for ReadItem optimization are included in the query predicate.
If a value can be missing at runtime, fall back to a SQL query (Where clause) instead of relying on ReadItem.

Example fix

// before
var u = await db.Users.FindAsync(partitionKey, id);  // id sometimes null
// after
if (id is null) return null;
var u = await db.Users.FindAsync(partitionKey, id);

Defensive patterns

Strategy: validation

Validate before calling

static async Task<T?> FindSafeAsync<T>(DbSet<T> set, object[] keys, CancellationToken ct)
    where T : class
{
    if (keys.Any(k => k is null || (k is string s && s.Length == 0)))
        throw new ArgumentException("all key parts must be non-null/non-empty", nameof(keys));
    return await set.FindAsync(keys, ct).AsTask().ConfigureAwait(false);
}

Type guard

static bool AllKeyPartsPresent(object[] keys)
    => keys.Length > 0 && keys.All(k => k is not null && (k is not string s || s.Length > 0));

Prevention

Keep key property configuration stable; avoid runtime key changes.
Pass fully-populated key tuples to Find.
Log the entity type and key values when a lookup fails to generate an id.

When it happens

Trigger: A ReadItem-shaped query executes against an entity whose key configuration or property values prevent generating an id (missing key property in projection, null constituent that short-circuits id generation, etc.).

Common situations: Changing the entity key configuration after deployment, projecting only some key properties, or passing a key value tuple where one element is missing.

Related errors

AI-assisted analysis of dotnet/efcore@3a2006ef56 (2026-08-11). Data as JSON: /api/errors/53deefeff1dbcdf6. Report an issue: GitHub.

Appendix: source

Thrown at src/EFCore.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable.cs:147

                    : null;
            }

            public T Current { get; private set; }

            public async ValueTask<bool> MoveNextAsync()
            {
                try
                {
                    using var _ = _concurrencyDetector?.EnterCriticalSection();

                    if (_hasExecuted)
                    {
                        return false;
                    }

                    if (!_readItemEnumerable.TryGetResourceId(out var resourceId))
                    {
                        throw new InvalidOperationException(CosmosStrings.ResourceIdMissing);
                    }

                    EntityFrameworkMetricsData.ReportQueryExecuting();

                    _response = await _cosmosQueryContext.CosmosClient.ExecuteReadItemAsync(
                            _cosmosContainer,
                            _cosmosPartitionKey,
                            resourceId,
                            _cosmosQueryContext.SessionTokenStorage,
                            _cancellationToken)
                        .ConfigureAwait(false);

                    return ShapeResult();
                }
                catch (Exception exception)
                {
                    if (_exceptionDetector.IsCancellation(exception, _cancellationToken))
                    {

View on GitHub (pinned to 3a2006ef56)