dotnet/efcore · error · ArgumentException

Invalid number of index sort order values: {numValues} value

Error message

Invalid number of index sort order values: {numValues} values were provided, but the index has {numProperties} properties.

What it means

Thrown by the IndexAttribute.IsDescending setter when the supplied bool[] length does not equal PropertyNames.Count. The index needs exactly one sort-direction flag per property so each column's order is unambiguous; any mismatch is a modeling configuration error. It surfaces during model building when EF Core (or your own code) processes the attribute.

Source

Thrown at src/EFCore.Abstractions/IndexAttribute.cs:69

    public bool IsUnique
    {
        get => _isUnique ?? false;
        set => _isUnique = value;
    }

    /// <summary>
    ///     A set of values indicating whether each corresponding index column has descending sort order.
    /// </summary>
    public bool[]? IsDescending
    {
        get;
        set
        {
            if (value is not null)
            {
                if (value.Length != PropertyNames.Count)
                {
                    throw new ArgumentException(
                        AbstractionsStrings.InvalidNumberOfIndexSortOrderValues(value.Length, PropertyNames.Count), nameof(IsDescending));
                }

                if (AllDescending)
                {
                    throw new ArgumentException(AbstractionsStrings.CannotSpecifyBothIsDescendingAndAllDescending);
                }
            }

            field = value;
        }
    }

    /// <summary>
    ///     Whether all index columns have descending sort order.
    /// </summary>
    public bool AllDescending
    {

View on GitHub (pinned to dbf9771522)

Solutions

1. Make the IsDescending array length equal to the number of properties in the index: one bool per property, in the same order.
2. If you want all columns descending, set AllDescending = true instead of IsDescending.
3. Double-check the property names list passed to the IndexAttribute constructor and align the IsDescending entries to it.

Example fix

// before
var idx = new IndexAttribute("FirstName", "LastName") { IsDescending = new[] { true } };

// after
var idx = new IndexAttribute("FirstName", "LastName") { IsDescending = new[] { true, false } };
// or, all descending:
var idx2 = new IndexAttribute("FirstName", "LastName") { AllDescending = true };

// Before assigning IsDescending, ensure one flag per property
if (isDescendingArray != null && isDescendingArray.Length != indexAttr.PropertyNames.Count)
{
    throw new InvalidOperationException(
        $"Expected {indexAttr.PropertyNames.Count} sort flags, got {isDescendingArray.Length}.");
}
indexAttr.IsDescending = isDescendingArray;

static bool IsValidIsDescending(IndexAttribute attr, bool[]? flags)
    => flags is null || flags.Length == attr.PropertyNames.Count;

When it happens

Trigger: Setting indexAttr.IsDescending to an array whose Length != the number of property names passed to the IndexAttribute constructor. For example, constructing new IndexAttribute("A", "B") then assigning IsDescending = new[] { true } (1 flag for a 2-property index).

Common situations: Adding a descending flag to a composite index but forgetting to provide a flag for every column. Refactoring an index from single to composite property and forgetting to extend the IsDescending array. Migrating code from AllDescending to per-column IsDescending.

Related errors

• IsDescending and AllDescending cannot both be specified on t
• The number argument cannot be a negative number.
• The value '{value}' provided for argument '{argumentName}' m
• Cosmos-specific methods can only be used when the context is
• A synchronous store management operation was performed and n

AI-assisted analysis of dotnet/efcore@dbf9771522 (2026-08-06). Data as JSON: /api/errors/6d983ea3785931fc. Report an issue: GitHub.