added new PhotoSizeType "J", fixed set market id

VkNet.Tests/Enum/StringEnums/StringEnumTests.cs

@@ -684,6 +684,10 @@ public void PhotoSizeTypeTest()
 		Utilities.Deserialize<PhotoSizeType>("e")
 			.Should()
 			.Be(PhotoSizeType.E);
+
+		Utilities.Deserialize<PhotoSizeType>("j")
+			.Should()
+			.Be(PhotoSizeType.J);
 	}
 
 	[Fact]

VkNet.Tests/Models/MarketModel.cs

@@ -0,0 +1,24 @@
+using FluentAssertions;
+using VkNet.Model;
+using Xunit;
+
+namespace VkNet.Tests.Models;
+
+public class MarketModel
+{
+	[Fact]
+	public void ToString_MarketShouldHaveIdAndAccessKey()
+	{
+		var market = new Market
+		{
+			Id = 1234,
+			OwnerId = 1234,
+			AccessKey = "test"
+		};
+
+		var result = market.ToString();
+
+		result.Should()
+			.Be("market1234_1234_test");
+	}
+}

VkNet/Enums/StringEnums/PhotoSizeType.cs

@@ -151,5 +151,13 @@ public enum PhotoSizeType
 	/// <remarks>
 	/// <see href="https://dev.vk.com/ru/reference/objects/photo-sizes">Документация</see>
 	/// </remarks>
-	L
+	L,
+
+	/// <summary>
+	/// В документации отсутствует описание
+	/// </summary>
+	/// <remarks>
+	/// <see href="https://dev.vk.com/ru/reference/objects/photo-sizes">Документация</see>
+	/// </remarks>
+	J
 }

VkNet/Model/Attachments/Market.cs

@@ -27,12 +27,7 @@ public class Market : MediaAttachment
 	{
 		get => _id;
 
-		set {
-			if (value is null)
-			{
-				_id ??= -1;
-			}
-		}
+		set => _id = value ?? -1;
 	}
 
 	/// <summary>
@@ -120,4 +115,19 @@ public class Market : MediaAttachment
 	[JsonProperty("button_title")]
 	[JsonConverter(typeof(SafetyEnumJsonConverter))]
 	public MarketItemButtonTitle ButtonTitle { get; set; }
+
+	/// <summary>
+	/// Преобразовать вложение в строку.
+	/// </summary>
+	/// <returns>
+	/// Строковое представление
+	/// </returns>
+	public override string ToString()
+	{
+		var result = $"{Alias}{OwnerId}_{Id}";
+
+		return string.IsNullOrWhiteSpace(AccessKey)
+			? result
+			: $"{result}_{AccessKey}";
+	}
 }