dotnet/efcore · error · ArgumentException

Invalid number of index sort order values

Error message

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

What it means

The IndexAttribute.IsDescending property accepts a bool[] that specifies ascending/descending sort order per column. EF Core requires the array length to exactly match the number of property names passed to the [Index] attribute constructor. This mismatch check prevents ambiguous or incomplete sort-order declarations during model building.

Solutions

Ensure the IsDescending array length equals the number of property names passed to the [Index] constructor (1st positional arg + all params).
If all columns should descend, use the AllDescending property instead of IsDescending.
If you only need default ascending order, omit IsDescending entirely.

Example fix

// before
[Index("IX_Order", "CustomerId", "OrderDate")]
public class Order { ... }
// elsewhere: attribute.IsDescending = new[] { true }; // 1 value for 2 columns

// after
[Index("IX_Order", "CustomerId", "OrderDate")]
public class Order { ... }
// elsewhere: attribute.IsDescending = new[] { true, false }; // matches 2 columns

Defensive patterns

Strategy: validation

Validate before calling

// Before assigning IsDescending, verify the array length matches the index property count
var attribute = new IndexAttribute("ColA", "ColB");
var sortOrders = new[] { true, false };
if (sortOrders.Length != attribute.PropertyNames.Count)
{
    throw new InvalidOperationException(
        $"IsDescending has {sortOrders.Length} values but index has {attribute.PropertyNames.Count} properties.");
}
attribute.IsDescending = sortOrders;

Prevention

When building IndexAttribute programmatically, derive the IsDescending array length from PropertyNames.Count.
Use AllDescending when all columns share the same sort direction.
Add a unit test that asserts IsDescending.Length == PropertyNames.Count for any programmatically built index.

When it happens

Trigger: Setting [Index("MyIndex", "ColA", "ColB")] and then assigning IsDescending = new[] { true } — the array has 1 element but the index declares 2 property names, so value.Length (1) != PropertyNames.Count (2).

Common situations: Adding or removing a column from a multi-column index without updating the IsDescending array; copy-pasting an [Index] attribute and changing property names but forgetting to update the sort-order array; refactoring a composite index.

Related errors

AI-assisted analysis of dotnet/efcore@3a2006ef56 (2026-08-11). Data as JSON: /api/errors/6d983ea3785931fc. Report an issue: GitHub.

Appendix: 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
    {

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