diff --git a/core/encoding/cyrillic-to-latin/cs/Common/Common.cs b/core/encoding/cyrillic-to-latin/cs/Common/Common.cs
new file mode 100644
index 00000000000..511ca3c3107
--- /dev/null
+++ b/core/encoding/cyrillic-to-latin/cs/Common/Common.cs
@@ -0,0 +1,15 @@
+using System;
+namespace CyrillicToLatin.Common
+{
+    public static class Common
+    {
+        public const string NoSourceOrDestinationFile = "There must be a source and a destination file.";
+
+        public const string FileDoesntExist = "The source file does not exist.";
+
+        public const string WrongDirectory = "Invalid directory: {0}";
+
+        public const string WrongIO = "I/O exception: {0}";
+    }
+}
+
diff --git a/core/encoding/cyrillic-to-latin/cs/ConsoleModule.cs b/core/encoding/cyrillic-to-latin/cs/ConsoleModule.cs
index 66864c65c49..a1b2cd71bf4 100644
--- a/core/encoding/cyrillic-to-latin/cs/ConsoleModule.cs
+++ b/core/encoding/cyrillic-to-latin/cs/ConsoleModule.cs
@@ -1,6 +1,9 @@
 using System;
 using System.IO;
+using System.Security.AccessControl;
 using System.Text;
+using CyrillicToLatin.Common;
+
 
 class ConsoleModule
 {
@@ -9,9 +12,9 @@ static void Main()
         string[] args = Environment.GetCommandLineArgs();
 
         // Get command line arguments.
-        if (args.Length != 3 || String.IsNullOrWhiteSpace(args[1]) || String.IsNullOrWhiteSpace(args[2]))
+        if (args.Length != 3 || string.IsNullOrWhiteSpace(args[1]) || string.IsNullOrWhiteSpace(args[2]))
         {
-            Console.WriteLine("There must be a source and a destination file.");
+            Console.WriteLine(Common.NoSourceOrDestinationFile);
             ShowSyntax();
             return;
         }
@@ -21,7 +24,7 @@ static void Main()
 
         if (!File.Exists(source))
         {
-            Console.WriteLine("The source file does not exist.");
+            Console.WriteLine(Common.NoSourceOrDestinationFile);
             return;
         }
 
@@ -74,12 +77,12 @@ static void Main()
         }
         catch (DirectoryNotFoundException e)
         {
-            Console.WriteLine($"Invalid directory: {e.Message}");
+            Console.WriteLine(Common.WrongDirectory);
             return;
         }
         catch (IOException e)
         {
-            Console.WriteLine($"I/O exception: {e.Message}");
+            Console.WriteLine(Common.WrongIO);
             return;
         }
     }
diff --git a/core/encoding/cyrillic-to-latin/cs/CyrillicToLatin.csproj b/core/encoding/cyrillic-to-latin/cs/CyrillicToLatin.csproj
index a4fb324cffe..92301346999 100644
--- a/core/encoding/cyrillic-to-latin/cs/CyrillicToLatin.csproj
+++ b/core/encoding/cyrillic-to-latin/cs/CyrillicToLatin.csproj
@@ -9,4 +9,10 @@
     <PackageReference Include="System.Text.Encoding.CodePages" Version="8.0.0" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Remove="Common\" />
+  </ItemGroup>
+  <ItemGroup>
+    <Folder Include="Common\" />
+  </ItemGroup>
 </Project>
diff --git a/core/encoding/cyrillic-to-latin/cs/CyrillicToLatinFallback.cs b/core/encoding/cyrillic-to-latin/cs/CyrillicToLatinFallback.cs
index 8fdee54dea8..c0d09e321c6 100644
--- a/core/encoding/cyrillic-to-latin/cs/CyrillicToLatinFallback.cs
+++ b/core/encoding/cyrillic-to-latin/cs/CyrillicToLatinFallback.cs
@@ -5,11 +5,11 @@
 
 class CyrillicToLatinFallback : EncoderFallback
 {
-    private Dictionary<Char, String> table;
+    private Dictionary<char, string> table;
 
     public CyrillicToLatinFallback()
     {
-        table = new Dictionary<Char, String>();
+        table = new Dictionary<char, string>();
         // Define mappings.
         // Uppercase modern Cyrillic characters.
         table.Add('\u0410', "A");
@@ -92,12 +92,12 @@ public override int MaxCharCount
 
 public class CyrillicToLatinFallbackBuffer : EncoderFallbackBuffer
 {
-    private Dictionary<Char, String> table;
+    private Dictionary<char, string> table;
     private int bufferIndex;
     private string buffer;
     private int leftToReturn;
 
-    internal CyrillicToLatinFallbackBuffer(Dictionary<Char, String> table)
+    internal CyrillicToLatinFallbackBuffer(Dictionary<char, string> table)
     {
         this.table = table;
         this.bufferIndex = -1;
@@ -153,4 +153,4 @@ public override int Remaining
     {
         get { return leftToReturn; }
     }
-}
+}
\ No newline at end of file
diff --git a/csharp/classes-quickstart/BankAccount.cs b/csharp/classes-quickstart/BankAccount.cs
index 6385c069d07..01ae6e84e36 100644
--- a/csharp/classes-quickstart/BankAccount.cs
+++ b/csharp/classes-quickstart/BankAccount.cs
@@ -1,11 +1,12 @@
 using System;
 using System.Collections.Generic;
+using classes.Contracts;
 
 namespace classes
 {
-    public class BankAccount
+    public class BankAccount : IBank
     {
-        public string Number { get; }
+        public string Number { get; set; }
         public string Owner { get; set; }
         #region BalanceComputation
         public decimal Balance
@@ -21,6 +22,7 @@ public decimal Balance
                 return balance;
             }
         }
+
         #endregion
 
         private static int accountNumberSeed = 1234567890;
@@ -36,7 +38,8 @@ public BankAccount(string name, decimal initialBalance)
         #endregion
 
         #region TransactionDeclaration
-        private List<Transaction> allTransactions = new List<Transaction>();
+
+        private List<ITransaction> allTransactions = new List<ITransaction>();
         #endregion
 
         #region DepositAndWithdrawal
@@ -82,4 +85,4 @@ public string GetAccountHistory()
         }
         #endregion
     }
-}
+}
\ No newline at end of file
diff --git a/csharp/classes-quickstart/Contracts/IBank.cs b/csharp/classes-quickstart/Contracts/IBank.cs
new file mode 100644
index 00000000000..ac1bcd4995a
--- /dev/null
+++ b/csharp/classes-quickstart/Contracts/IBank.cs
@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+
+namespace classes.Contracts
+{
+    public interface IBank
+    {
+        public string Number { get; }
+
+        public string Owner { get; }
+
+        public decimal Balance { get; }
+    }
+}
\ No newline at end of file
diff --git a/csharp/classes-quickstart/Contracts/ITransaction.cs b/csharp/classes-quickstart/Contracts/ITransaction.cs
new file mode 100644
index 00000000000..02c4d382a44
--- /dev/null
+++ b/csharp/classes-quickstart/Contracts/ITransaction.cs
@@ -0,0 +1,12 @@
+using System;
+namespace classes.Contracts
+{
+    public interface ITransaction
+    {
+        public decimal Amount { get; }
+
+        public DateTime Date { get; }
+
+        public string Notes { get; }
+    }
+}
\ No newline at end of file
diff --git a/csharp/classes-quickstart/classes.csproj b/csharp/classes-quickstart/classes.csproj
index 120e38c3150..5c938e63a4c 100644
--- a/csharp/classes-quickstart/classes.csproj
+++ b/csharp/classes-quickstart/classes.csproj
@@ -5,4 +5,10 @@
     <TargetFramework>net7.0</TargetFramework>
   </PropertyGroup>
 
+  <ItemGroup>
+    <None Remove="Contracts\" />
+  </ItemGroup>
+  <ItemGroup>
+    <Folder Include="Contracts\" />
+  </ItemGroup>
 </Project>
diff --git a/csharp/classes-quickstart/transaction.cs b/csharp/classes-quickstart/transaction.cs
index 198418c62dd..ca256132329 100644
--- a/csharp/classes-quickstart/transaction.cs
+++ b/csharp/classes-quickstart/transaction.cs
@@ -1,12 +1,13 @@
 using System;
+using classes.Contracts;
 
 namespace classes
 {
-    public class Transaction
+    public class Transaction : ITransaction
     {
-        public decimal Amount { get; }
+        public decimal Amount { get; set; }
         public DateTime Date { get; }
-        public string Notes { get; }
+        public string Notes { get; set; }
 
         public Transaction(decimal amount, DateTime date, string note)
         {
@@ -15,4 +16,4 @@ public Transaction(decimal amount, DateTime date, string note)
             this.Notes = note;
         }
     }
-}
+}                           
\ No newline at end of file