dotnet/efcore · error · InvalidOperationException

' . ' and ' . ' are both mapped to column ' ' in ' ', but…

Error message

'{entityType1}.{property1}' and '{entityType2}.{property2}' are both mapped to column '{columnName}' in '{table}', but are configured with different comments ('{comment1}' and '{comment2}').

What it means

Two properties mapped to the same column declare different column comments via HasComment. The physical column can carry only one comment, so EF requires them to match exactly (compared with StringComparison.Ordinal, so case and whitespace matter).

Solutions

Set the identical HasComment text on both properties.
Remove HasComment from one side so both fall back to empty.
If distinct documentation is genuinely needed, remap one property to a distinct column.

Example fix

// before
modelBuilder.Entity<Customer>().Property(c => c.Ref).HasComment("Customer reference");
modelBuilder.Entity<CustomerFlags>().Property(f => f.Ref).HasComment("Customer ref"); // shared, case/wording differs

// after
modelBuilder.Entity<Customer>().Property(c => c.Ref).HasComment("Customer reference");
modelBuilder.Entity<CustomerFlags>().Property(f => f.Ref).HasComment("Customer reference");

Defensive patterns

Strategy: validation

Validate before calling

foreach (var (col, props) in sharedColumnGroups)
{
    var comments = props.Select(p => p.GetComment(storeObject) ?? "").Distinct(StringComparer.Ordinal).ToList();
    if (comments.Count > 1)
        Console.WriteLine($"Column {col} has conflicting comments");
}

Try / catch

try { _ = db.Model; } catch (InvalidOperationException ex) when (ex.Message.Contains("different comments")) { // align HasComment on both properties }

Prevention

Maintain column comments in one place; reference the same string on shared columns.
Remember comments compare case-sensitively; standardize wording.
Smoke-test the model at startup.

When it happens

Trigger: ValidateCompatible() reads property.GetComment(storeObject) and duplicateProperty.GetComment(storeObject) (null coerced to empty); an Ordinal inequality throws. Happens when two entities sharing a column each call HasComment with different text.

Common situations: Documentation refresh on one entity but not its table-splitting partner; localization of comments applied to only one side; scaffolding that imported comments only for the principal entity.

Related errors

AI-assisted analysis of dotnet/efcore@3a2006ef56 (2026-08-11). Data as JSON: /api/errors/04283b8b1ee08990. Report an issue: GitHub.

Appendix: source

Thrown at src/EFCore.Relational/Infrastructure/RelationalModelValidator.cs:1748

        if (!currentDefaultValueSql.Equals(previousDefaultValueSql, StringComparison.OrdinalIgnoreCase))
        {
            throw new InvalidOperationException(
                RelationalStrings.DuplicateColumnNameDefaultSqlMismatch(
                    duplicateProperty.DeclaringType.DisplayName(),
                    duplicateProperty.Name,
                    property.DeclaringType.DisplayName(),
                    property.Name,
                    columnName,
                    storeObject.DisplayName(),
                    previousDefaultValueSql,
                    currentDefaultValueSql));
        }

        var currentComment = property.GetComment(storeObject) ?? "";
        var previousComment = duplicateProperty.GetComment(storeObject) ?? "";
        if (!currentComment.Equals(previousComment, StringComparison.Ordinal))
        {
            throw new InvalidOperationException(
                RelationalStrings.DuplicateColumnNameCommentMismatch(
                    duplicateProperty.DeclaringType.DisplayName(),
                    duplicateProperty.Name,
                    property.DeclaringType.DisplayName(),
                    property.Name,
                    columnName,
                    storeObject.DisplayName(),
                    previousComment,
                    currentComment));
        }

        var currentCollation = property.GetCollation(storeObject) ?? "";
        var previousCollation = duplicateProperty.GetCollation(storeObject) ?? "";
        if (!currentCollation.Equals(previousCollation, StringComparison.Ordinal))
        {
            throw new InvalidOperationException(
                RelationalStrings.DuplicateColumnNameCollationMismatch(
                    duplicateProperty.DeclaringType.DisplayName(),

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