feat: Add LINQ filtering examples to GettingStartedWithTextSearch sample

- Add BingSearchWithLinqFilteringAsync() and GoogleSearchWithLinqFilteringAsync() demonstrating ITextSearch<TRecord> with type-safe LINQ filtering
- Add XML documentation following Microsoft standards for all public properties
- Include C# 14 compatibility guidance for Contains() method usage in filtering examples
- Maintain backward compatibility with existing simple search examples

Addresses #10456

Author: alzarei

dotnet/samples/GettingStartedWithTextSearch/InMemoryVectorStoreFixture.cs

@@ -15,12 +15,24 @@ namespace GettingStartedWithTextSearch;
 /// </summary>
 public class InMemoryVectorStoreFixture : IAsyncLifetime
 {
+    /// <summary>
+    /// Gets the embedding generator used for creating vector embeddings.
+    /// </summary>
     public IEmbeddingGenerator<string, Embedding<float>> EmbeddingGenerator { get; private set; }
 
+    /// <summary>
+    /// Gets the in-memory vector store instance.
+    /// </summary>
     public InMemoryVectorStore InMemoryVectorStore { get; private set; }
 
+    /// <summary>
+    /// Gets the vector store record collection for data models.
+    /// </summary>
     public VectorStoreCollection<Guid, DataModel> VectorStoreRecordCollection { get; private set; }
 
+    /// <summary>
+    /// Gets the name of the collection used for storing records.
+    /// </summary>
     public string CollectionName => "records";
 
     /// <summary>
@@ -138,21 +150,36 @@ private async Task<VectorStoreCollection<TKey, TRecord>> CreateCollectionFromLis
     /// </remarks>
     public sealed class DataModel
     {
+        /// <summary>
+        /// Gets or sets the unique identifier for this record.
+        /// </summary>
         [VectorStoreKey]
         [TextSearchResultName]
         public Guid Key { get; init; }
 
+        /// <summary>
+        /// Gets or sets the text content of this record.
+        /// </summary>
         [VectorStoreData]
         [TextSearchResultValue]
         public string Text { get; init; }
 
+        /// <summary>
+        /// Gets or sets the link associated with this record.
+        /// </summary>
         [VectorStoreData]
         [TextSearchResultLink]
         public string Link { get; init; }
 
+        /// <summary>
+        /// Gets or sets the tag for categorizing this record.
+        /// </summary>
         [VectorStoreData(IsIndexed = true)]
         public required string Tag { get; init; }
 
+        /// <summary>
+        /// Gets the embedding representation of the text content.
+        /// </summary>
         [VectorStoreVector(1536)]
         public string Embedding => Text;
     }

dotnet/samples/GettingStartedWithTextSearch/Step1_Web_Search.cs

@@ -53,6 +53,79 @@ public async Task GoogleSearchAsync()
         }
     }
 
+    /// <summary>
+    /// Show how to use <see cref="BingTextSearch"/> with the new generic <see cref="ITextSearch{TRecord}"/>
+    /// interface and LINQ filtering for type-safe searches.
+    /// </summary>
+    [Fact]
+    public async Task BingSearchWithLinqFilteringAsync()
+    {
+        // Create a BingTextSearch instance
+        var bingSearch = new BingTextSearch(apiKey: TestConfiguration.Bing.ApiKey);
+
+        // Use the new generic interface for type-safe searches
+        ITextSearch<BingWebPage> textSearch = bingSearch;
+
+        var query = "What is the Semantic Kernel?";
+
+        // Use LINQ filtering for type-safe search with compile-time validation
+        var options = new TextSearchOptions<BingWebPage>
+        {
+            Top = 4,
+            Filter = page => page.Language == "en" && page.IsFamilyFriendly == true
+        };
+
+        // Search and return strongly-typed results
+        Console.WriteLine("\n--- Bing Search with LINQ Filtering ---\n");
+        KernelSearchResults<BingWebPage> searchResults = await textSearch.GetSearchResultsAsync(query, options);
+        await foreach (BingWebPage page in searchResults.Results)
+        {
+            Console.WriteLine($"Name: {page.Name}");
+            Console.WriteLine($"Snippet: {page.Snippet}");
+            Console.WriteLine($"Url: {page.Url}");
+            Console.WriteLine($"Language: {page.Language}");
+            Console.WriteLine($"Family Friendly: {page.IsFamilyFriendly}");
+            Console.WriteLine("---");
+        }
+    }
+
+    /// <summary>
+    /// Show how to use <see cref="GoogleTextSearch"/> with the new generic <see cref="ITextSearch{TRecord}"/>
+    /// interface and LINQ filtering for type-safe searches.
+    /// </summary>
+    [Fact]
+    public async Task GoogleSearchWithLinqFilteringAsync()
+    {
+        // Create a GoogleTextSearch instance
+        var googleSearch = new GoogleTextSearch(
+            searchEngineId: TestConfiguration.Google.SearchEngineId,
+            apiKey: TestConfiguration.Google.ApiKey);
+
+        // Use the new generic interface for type-safe searches
+        ITextSearch<GoogleWebPage> textSearch = googleSearch;
+
+        var query = "What is the Semantic Kernel?";
+
+        // Use LINQ filtering for type-safe search with compile-time validation
+        var options = new TextSearchOptions<GoogleWebPage>
+        {
+            Top = 4,
+            Filter = page => page.Title.Contains("Semantic") && page.DisplayLink.EndsWith(".com")
+        };
+
+        // Search and return strongly-typed results
+        Console.WriteLine("\n--- Google Search with LINQ Filtering ---\n");
+        KernelSearchResults<GoogleWebPage> searchResults = await textSearch.GetSearchResultsAsync(query, options);
+        await foreach (GoogleWebPage page in searchResults.Results)
+        {
+            Console.WriteLine($"Title: {page.Title}");
+            Console.WriteLine($"Snippet: {page.Snippet}");
+            Console.WriteLine($"Link: {page.Link}");
+            Console.WriteLine($"Display Link: {page.DisplayLink}");
+            Console.WriteLine("---");
+        }
+    }
+
     /// <summary>
     /// Show how to create a <see cref="BingTextSearch"/> and use it to perform a search
     /// and return results as a collection of <see cref="BingWebPage"/> instances.
@@ -86,7 +159,7 @@ public async Task SearchForWebPagesAsync()
         }
         else
         {
-            Console.WriteLine("\n——— Google Web Page Results ———\n");
+            Console.WriteLine("\n��� Google Web Page Results ���\n");
             await foreach (Google.Apis.CustomSearchAPI.v1.Data.Result result in objectResults.Results)
             {
                 Console.WriteLine($"Title:       {result.Title}");