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@alzarei alzarei commented Sep 24, 2025

Add generic ITextSearch interface with LINQ filtering support

Addresses Issue #10456: Modernize ITextSearch to use LINQ-based vector search filtering

** Multi-PR Strategy Context**
This is PR 1 of multiple in a structured implementation approach for Issue #10456. This PR targets the feature/issue-10456-linq-filtering branch for incremental review and testing before the final submission to Microsoft's main branch.

This approach enables focused code review, easier debugging, and safer integration of the comprehensive ITextSearch modernization.

Motivation and Context

Why is this change required?
The current ITextSearch interface uses legacy TextSearchFilter which requires conversion to obsolete VectorSearchFilter, creating technical debt and performance overhead. Issue #10456 requests modernization to use type-safe LINQ filtering with Expression<Func<TRecord, bool>>.

What problem does it solve?

  • Eliminates runtime errors from property name typos in filters
  • Removes performance overhead from obsolete filter conversions
  • Provides compile-time type safety and IntelliSense support
  • Modernizes the API to follow .NET best practices for LINQ-based filtering

What scenario does it contribute to?
This enables developers to write type-safe text search filters like:

var options = new TextSearchOptions<Article>
{
    Filter = article => article.Category == "Technology" && article.PublishedDate > DateTime.Now.AddDays(-30)
};

Issue Link: #10456

Description

This PR introduces foundational generic interfaces to enable LINQ-based filtering for text search operations. The implementation follows an additive approach, maintaining 100% backward compatibility while providing a modern, type-safe alternative.

Overall Approach:

  • Add generic ITextSearch<TRecord> interface alongside existing non-generic version
  • Add generic TextSearchOptions<TRecord> with LINQ Expression<Func<TRecord, bool>>? Filter
  • Update VectorStoreTextSearch to implement both interfaces
  • Preserve all existing functionality while enabling modern LINQ filtering

Underlying Design:

  • Zero Breaking Changes: Legacy interfaces remain unchanged and fully functional
  • Gradual Migration: Teams can adopt generic interfaces at their own pace
  • Performance Optimization: Eliminates obsolete VectorSearchFilter conversion overhead
  • Type Safety: Compile-time validation prevents runtime filter errors

Engineering Approach: Following Microsoft's Established Patterns

This solution was not created from scratch but carefully architected by studying and extending Microsoft's existing patterns within the Semantic Kernel codebase:

1. Pattern Discovery: VectorSearchOptions Template

Found the exact migration pattern Microsoft established in PR #10273:

public class VectorSearchOptions<TRecord>
{
    [Obsolete("Use Filter instead")]
    public VectorSearchFilter? OldFilter { get; set; }  // Legacy approach

    public Expression<Func<TRecord, bool>>? Filter { get; set; }  // Modern LINQ approach
}

2. Existing Infrastructure Analysis

Discovered that VectorStoreTextSearch.cs already had the implementation infrastructure:

// Modern LINQ filtering method (already existed!)
private async IAsyncEnumerable<VectorSearchResult<TRecord>> ExecuteVectorSearchAsync(
    string query,
    TextSearchOptions<TRecord>? searchOptions,  // Generic options
    CancellationToken cancellationToken)
{
    var vectorSearchOptions = new VectorSearchOptions<TRecord>
    {
        Filter = searchOptions.Filter,  // Direct LINQ filtering - no conversion!
    };
}

3. Microsoft's Additive Migration Strategy

Followed the exact pattern used across the codebase:

  • Keep legacy interface unchanged for backward compatibility
  • Add generic interface with modern features alongside
  • Use [Experimental] attributes for new features
  • Provide gradual migration path

4. Consistency with Existing Filter Translators

All vector database connectors (AzureAISearch, Qdrant, MongoDB, Weaviate) use the same pattern:

internal Filter Translate(LambdaExpression lambdaExpression, CollectionModel model)
{
    // All work with Expression<Func<TRecord, bool>>
    // All provide compile-time safety
    // All follow the same LINQ expression pattern
}

5. Technical Debt Elimination

The existing problematic code that this PR enables fixing in PR #2:

// Current technical debt in VectorStoreTextSearch.cs
#pragma warning disable CS0618 // VectorSearchFilter is obsolete
OldFilter = searchOptions.Filter?.FilterClauses is not null
    ? new VectorSearchFilter(searchOptions.Filter.FilterClauses)
    : null,
#pragma warning restore CS0618

This will be replaced with direct LINQ filtering: Filter = searchOptions.Filter

Result: This solution extends Microsoft's established patterns consistently rather than introducing new conventions, ensuring seamless integration with the existing ecosystem.

Summary

This PR introduces the foundational generic interfaces needed to modernize text search functionality from legacy TextSearchFilter to type-safe LINQ Expression<Func<TRecord, bool>> filtering. This is the first in a series of PRs to completely resolve Issue #10456.

Key Changes

New Generic Interfaces

  • ITextSearch<TRecord>: Generic interface with type-safe LINQ filtering

    • SearchAsync<TRecord>(string query, TextSearchOptions<TRecord> options, CancellationToken cancellationToken)
    • GetTextSearchResultsAsync<TRecord>(string query, TextSearchOptions<TRecord> options, CancellationToken cancellationToken)
    • GetSearchResultsAsync<TRecord>(string query, TextSearchOptions<TRecord> options, CancellationToken cancellationToken)
  • TextSearchOptions<TRecord>: Generic options class with LINQ support

    • Expression<Func<TRecord, bool>>? Filter property for compile-time type safety
    • Comprehensive XML documentation with usage examples

Enhanced Implementation

  • VectorStoreTextSearch<TValue>: Now implements both generic and legacy interfaces
    • Maintains full backward compatibility with existing ITextSearch
    • Adds native support for generic ITextSearch<TValue> with direct LINQ filtering
    • Eliminates technical debt from TextSearchFilter → obsolete VectorSearchFilter conversion

Benefits

Type Safety & Developer Experience

  • Compile-time validation of filter expressions
  • IntelliSense support for record property access
  • Eliminates runtime errors from property name typos

Performance Improvements

  • Direct LINQ filtering without obsolete conversion overhead
  • Reduced object allocations by eliminating intermediate filter objects
  • More efficient vector search operations

Zero Breaking Changes

  • 100% backward compatibility - existing code continues to work unchanged
  • Legacy interfaces preserved - ITextSearch and TextSearchOptions untouched
  • Gradual migration path - teams can adopt generic interfaces at their own pace

Implementation Strategy

This PR implements Phase 1 of the Issue #10456 resolution across 6 structured PRs:

  1. [DONE] PR 1 (This PR): Core generic interface additions

    • Add ITextSearch<TRecord> and TextSearchOptions<TRecord> interfaces
    • Update VectorStoreTextSearch to implement both legacy and generic interfaces
    • Maintain 100% backward compatibility
  2. [TODO] PR 2: VectorStoreTextSearch internal modernization

    • Remove obsolete VectorSearchFilter conversion overhead
    • Use LINQ expressions directly in internal implementation
    • Eliminate technical debt identified in original issue
  3. [TODO] PR 3: Modernize BingTextSearch connector

    • Update BingTextSearch.cs to implement ITextSearch<TRecord>
    • Adapt LINQ expressions to Bing API filtering capabilities
    • Ensure feature parity between legacy and generic interfaces
  4. [TODO] PR 4: Modernize GoogleTextSearch connector

    • Update GoogleTextSearch.cs to implement ITextSearch<TRecord>
    • Adapt LINQ expressions to Google API filtering capabilities
    • Maintain backward compatibility for existing integrations
  5. [TODO] PR 5: Modernize remaining connectors

    • Update TavilyTextSearch.cs and BraveTextSearch.cs
    • Complete connector ecosystem modernization
    • Ensure consistent LINQ filtering across all text search providers
  6. [TODO] PR 6: Tests and samples modernization

    • Update 40+ test files identified in impact assessment
    • Modernize sample applications to demonstrate LINQ filtering
    • Validate complete feature parity and performance improvements

Verification Results

Microsoft Official Pre-Commit Compliance

[PASS] dotnet build --configuration Release         # 0 warnings, 0 errors
[PASS] dotnet test --configuration Release          # 1,574/1,574 tests passed (100%)
[PASS] dotnet format SK-dotnet.slnx --verify-no-changes  # 0/10,131 files needed formatting

Test Coverage

  • VectorStoreTextSearch: 19/19 tests passing (100%)
  • TextSearch Integration: 82/82 tests passing (100%)
  • Full Unit Test Suite: 1,574/1,574 tests passing (100%)
  • No regressions detected

Code Quality

  • Static Analysis: 0 compiler warnings, 0 errors
  • Formatting: Perfect adherence to .NET coding standards
  • Documentation: Comprehensive XML docs with usage examples

Example Usage

Before (Legacy)

var options = new TextSearchOptions
{
    Filter = new TextSearchFilter().Equality("Category", "Technology")
};
var results = await textSearch.SearchAsync("AI advances", options);

After (Generic with LINQ)

var options = new TextSearchOptions<Article>
{
    Filter = article => article.Category == "Technology"
};
var results = await textSearch.SearchAsync("AI advances", options);

Files Modified

dotnet/src/SemanticKernel.Abstractions/Data/TextSearch/ITextSearch.cs
dotnet/src/SemanticKernel.Abstractions/Data/TextSearch/TextSearchOptions.cs
dotnet/src/SemanticKernel.Core/Data/TextSearch/VectorStoreTextSearch.cs

Contribution Checklist

Verification Evidence:

  • Build: dotnet build --configuration Release - 0 warnings, 0 errors
  • Tests: dotnet test --configuration Release - 1,574/1,574 tests passed (100%)
  • Formatting: dotnet format SK-dotnet.slnx --verify-no-changes - 0/10,131 files needed formatting
  • Compatibility: All existing tests pass, no breaking changes introduced

Issue: #10456
Type: Enhancement (Feature Addition)
Breaking Changes: None
Documentation: Updated with comprehensive XML docs and usage examples

- Add ITextSearch<TRecord> generic interface with type-safe LINQ filtering
- Add TextSearchOptions<TRecord> with Expression<Func<TRecord, bool>>? Filter property
- Update VectorStoreTextSearch to implement both generic and legacy interfaces
- Maintain full backward compatibility with existing ITextSearch interface
- Enable compile-time type safety and eliminate TextSearchFilter conversion overhead

Addresses microsoft#10456
@moonbox3 moonbox3 added .NET Issue or Pull requests regarding .NET code kernel.core labels Sep 24, 2025
@github-actions github-actions bot changed the title feat: Add generic ITextSearch<TRecord> interface with LINQ filtering (microsoft#10456) .Net: feat: Add generic ITextSearch<TRecord> interface with LINQ filtering (microsoft#10456) Sep 24, 2025
@alzarei alzarei marked this pull request as ready for review September 24, 2025 09:42
@alzarei alzarei requested a review from a team as a code owner September 24, 2025 09:42
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alzarei commented Sep 25, 2025

@alzarei please read the following Contributor License Agreement(CLA). If you agree with the CLA, please reply with the following information.

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alzarei commented Sep 25, 2025

@microsoft-github-policy-service agree

@alzarei alzarei changed the title .Net: feat: Add generic ITextSearch<TRecord> interface with LINQ filtering (microsoft#10456) .Net: feat: Implement type-safe LINQ filtering for ITextSearch interface (microsoft#10456) Sep 25, 2025
@alzarei alzarei marked this pull request as draft September 25, 2025 04:40
@alzarei alzarei marked this pull request as ready for review September 25, 2025 04:40
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alzarei commented Sep 25, 2025

@markwallace-microsoft @moonbox3 can you please trigger the Merge Gatekeeper again? Thanks!

@markwallace-microsoft markwallace-microsoft merged commit b94f3f3 into microsoft:feature-text-search-linq Sep 25, 2025
14 of 15 checks passed
markwallace-microsoft pushed a commit that referenced this pull request Nov 3, 2025
…arch.GetSearchResultsAsync (#13318)

This PR enhances the type safety of the `ITextSearch<TRecord>` interface
by changing the `GetSearchResultsAsync` method to return
`KernelSearchResults<TRecord>` instead of `KernelSearchResults<object>`.
This improvement eliminates the need for manual casting and provides
better IntelliSense support for consumers.

## Motivation and Context

The current implementation of
`ITextSearch<TRecord>.GetSearchResultsAsync` returns
`KernelSearchResults<object>`, which requires consumers to manually cast
results to the expected type. This reduces type safety and degrades the
developer experience by losing compile-time type checking and
IntelliSense support.

This change aligns the return type with the generic type parameter
`TRecord`, providing the expected strongly-typed results that users of a
generic interface would anticipate.

## Changes Made

### Interface (ITextSearch.cs)
- Changed `ITextSearch<TRecord>.GetSearchResultsAsync` return type from
`KernelSearchResults<object>` to `KernelSearchResults<TRecord>`
- Updated XML documentation to reflect strongly-typed return value
- Legacy `ITextSearch` interface (non-generic) remains unchanged,
continuing to return `KernelSearchResults<object>` for backward
compatibility

### Implementation (VectorStoreTextSearch.cs)
- Added new `GetResultsAsTRecordAsync` helper method returning
`IAsyncEnumerable<TRecord>`
- Updated generic interface implementation to use the new strongly-typed
helper
- Retained `GetResultsAsRecordAsync` method for the legacy non-generic
interface

### Tests (VectorStoreTextSearchTests.cs)
- Updated 3 unit tests to use strongly-typed `DataModel` or
`DataModelWithRawEmbedding` instead of `object`
- Improved test assertions to leverage direct property access without
casting
- All 19 tests pass successfully

## Breaking Changes

**Interface Change (Experimental API):**
- `ITextSearch<TRecord>.GetSearchResultsAsync` now returns
`KernelSearchResults<TRecord>` instead of `KernelSearchResults<object>`
- This interface is marked with `[Experimental("SKEXP0001")]`,
indicating that breaking changes are expected during the preview period
- Legacy `ITextSearch` interface (non-generic) is unaffected and
maintains full backward compatibility

## Benefits

- **Improved Type Safety**: Eliminates runtime casting errors by
providing compile-time type checking
- **Enhanced Developer Experience**: Full IntelliSense support for
TRecord properties and methods
- **Cleaner Code**: Consumers no longer need to cast results from object
to the expected type
- **Consistent API Design**: Generic interface now behaves as expected,
returning strongly-typed results
- **Zero Impact on Legacy Code**: Non-generic ITextSearch interface
remains unchanged

## Testing

- All 19 existing unit tests pass
- Updated tests demonstrate improved type safety with direct property
access
- Verified both generic and legacy interfaces work correctly
- Confirmed zero breaking changes to non-generic ITextSearch consumers

## Related Work

This PR is part of the Issue #10456 multi-PR chain for modernizing
ITextSearch with LINQ-based filtering:
- PR #13175: Foundation (ITextSearch<TRecord> interface) - Merged
- PR #13179: VectorStoreTextSearch + deprecation pattern - In Review
- **This PR (2.1)**: API refinement for improved type safety
- PR #13188-13191: Connector migrations (Bing, Google, Tavily, Brave) -
Pending
- PR #13194: Samples and documentation - Pending

All PRs target the `feature-text-search-linq` branch for coordinated
release.

## Migration Guide for Consumers

### Before (Previous API)
```csharp
ITextSearch<DataModel> search = ...;
KernelSearchResults<object> results = await search.GetSearchResultsAsync("query", options);

foreach (var obj in results.Results)
{
    var record = (DataModel)obj;  // Manual cast required
    Console.WriteLine(record.Name);
}
```

### After (Improved API)
```csharp
ITextSearch<DataModel> search = ...;
KernelSearchResults<DataModel> results = await search.GetSearchResultsAsync("query", options);

foreach (var record in results.Results)  // Strongly typed!
{
    Console.WriteLine(record.Name);  // Direct property access with IntelliSense
}
```

## Checklist

- [x] Changes build successfully
- [x] All unit tests pass (19/19)
- [x] XML documentation updated
- [x] Breaking change documented (experimental API only)
- [x] Legacy interface backward compatibility maintained
- [x] Code follows project coding standards

Co-authored-by: Alexander Zarei <alzarei@users.noreply.github.com>
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