updated Filter endpoint - added publisher

WebAPI/Controllers/BookController.cs

@@ -162,7 +162,14 @@ namespace WebAPI.Controllers
 
         [HttpGet]
         [Route("filter")]
-        public async Task<IActionResult> FilterBooks(string? name, string? description, decimal? minPrice, decimal? maxPrice, BookGenre? genre, int? authorId)
+        public async Task<IActionResult> FilterBooks(
+        string? name,
+        string? description,
+        decimal? minPrice,
+        decimal? maxPrice,
+        BookGenre? genre,
+        int? authorId,
+        string? publisher)
         {
             var query = _dbContext.Books.AsQueryable();
 
@@ -196,6 +203,11 @@ namespace WebAPI.Controllers
                 query = query.Where(book => book.AuthorId == authorId);
             }
 
+            if (!string.IsNullOrWhiteSpace(publisher))
+            {
+                query = query.Where(book => book.Publisher.Contains(publisher));
+            }
+
             var filteredBooks = await query.ToListAsync();
 
             if (!filteredBooks.Any())