dotnet/efcore · error · InvalidOperationException

Property ' . ' was configured for full-text search, but has…

Error message

Property '{entityType}.{property}' was configured for full-text search, but has type '{clrType}'; only string properties can be configured for full-text search.

What it means

CosmosClientWrapper throws FullTextSearchConfiguredForUnsupportedPropertyType when generating full-text paths and finds a property configured for full-text search whose ClrType is not string. Cosmos DB full-text search supports only string properties; applying it to any other CLR type is rejected at create-container time.

Solutions

Move the full-text configuration to a string property.
Change the property's CLR type to string if full-text search is required on that data.
Serialize the searchable content into a dedicated string column and index that.

Example fix

// before - Content is byte[]
modelBuilder.Entity<Doc>().Property(x => x.Content).IsFullText();

// after - Text is string and holds searchable content
modelBuilder.Entity<Doc>().Property(x => x.Text).IsFullText();

Defensive patterns

Strategy: validation

Validate before calling

// At model build, assert full-text-configured properties are strings.
foreach (var prop in entityType.GetProperties())
{
    if (prop.IsFullText() == true && prop.ClrType != typeof(string))
        throw new InvalidOperationException($"{entityType.DisplayName()}.{prop.Name} ({prop.ClrType.Name}) cannot be full-text indexed; only string is supported.");
}

Type guard

static bool CanBeFullTextIndexed(IProperty p) => p.ClrType == typeof(string);

Prevention

Apply full-text configuration only to string properties.
Add a model-build validator that rejects full-text on non-string properties.
Store searchable content in a dedicated string column when the source is non-string.

When it happens

Trigger: Marking a non-string property (int, byte[], Json, GUID, etc.) as full-text searchable in OnModelCreating.

Common situations: Accidentally applying IsFullText to a binary/JSON payload column; applying full-text configuration to the wrong property; copy-paste from a string property to a non-string one.

Related errors

AI-assisted analysis of dotnet/efcore@3a2006ef56 (2026-08-11). Data as JSON: /api/errors/d4f50b014f9f6353. Report an issue: GitHub.

Appendix: source

Thrown at src/EFCore.Cosmos/Storage/Internal/CosmosClientWrapper.cs:250

                        ? CompositePathSortOrder.Descending
                        : CompositePathSortOrder.Ascending;
                    compositePaths.Add(new CompositePath { Path = path, Order = order });
                    key.Append(path).Append('=').Append(order).Append('|');
                }

                if (seenCompositeIndexes.Add(key.ToString()))
                {
                    compositeIndexes.Add(compositePaths);
                }
            }
        }

        var fullTextPaths = new Collection<FullTextPath>();
        foreach (var (property, language) in parameters.FullTextProperties)
        {
            if (property.ClrType != typeof(string))
            {
                throw new InvalidOperationException(
                    CosmosStrings.FullTextSearchConfiguredForUnsupportedPropertyType(
                        property.DeclaringType.DisplayName(),
                        property.Name,
                        property.ClrType.Name));
            }

            fullTextPaths.Add(
                new FullTextPath
                {
                    Path = GetJsonPropertyPathFromRoot(property),
                    // TODO: remove the fallback once Cosmos SDK allows optional language (see #35939)
                    Language = language ?? parameters.DefaultFullTextLanguage ?? "en-US"
                });
        }

        var embeddings = new Collection<Embedding>();
        foreach (var (property, vectorType) in parameters.Vectors)
        {

View on GitHub (pinned to 3a2006ef56)