diff --git a/S7.Net.UnitTest/S7NetTestsAsync.cs b/S7.Net.UnitTest/S7NetTestsAsync.cs
index 31f99eb..86d7f22 100644
--- a/S7.Net.UnitTest/S7NetTestsAsync.cs
+++ b/S7.Net.UnitTest/S7NetTestsAsync.cs
@@ -160,6 +160,31 @@ namespace S7.Net.UnitTest
             Assert.AreEqual(tc.DWordVariable, tc2.DWordVariable);
         }
 
+        [TestMethod]
+        public async Task Test_Async_ReadAndWriteNestedClass()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            TestClassWithNestedClass tc = new TestClassWithNestedClass
+            {
+                BitVariable00 = true,
+                BitVariable01 = new TestClassInnerWithBool { BitVariable00 = true },
+                ByteVariable02 = new TestClassInnerWithByte { ByteVariable00 = 128 },
+                BitVariable03 = true,
+                ShortVariable04 = new TestClassInnerWithShort { ShortVarialbe00 = -15000 }
+            };
+
+            await plc.WriteClassAsync(tc, DB4);
+            TestClassWithNestedClass tc2 = new TestClassWithNestedClass();
+            // Values that are read from a class are stored inside the class itself, that is passed by reference
+            await plc.ReadClassAsync(tc2, DB4);
+            Assert.AreEqual(tc.BitVariable00, tc2.BitVariable00);
+            Assert.AreEqual(tc.BitVariable01.BitVariable00, tc2.BitVariable01.BitVariable00);
+            Assert.AreEqual(tc.ByteVariable02.ByteVariable00, tc2.ByteVariable02.ByteVariable00);
+            Assert.AreEqual(tc.BitVariable03, tc2.BitVariable03);
+            Assert.AreEqual(tc.ShortVariable04.ShortVarialbe00, tc2.ShortVariable04.ShortVarialbe00);
+        }
+
         /// <summary>
         /// Read/Write a struct that has the same properties of a DB with the same field in the same order
         /// </summary>
diff --git a/S7.Net.UnitTest/S7NetTestsSync.cs b/S7.Net.UnitTest/S7NetTestsSync.cs
index 1b648f2..c096643 100644
--- a/S7.Net.UnitTest/S7NetTestsSync.cs
+++ b/S7.Net.UnitTest/S7NetTestsSync.cs
@@ -718,6 +718,31 @@ namespace S7.Net.UnitTest
             Assert.AreEqual(tc.ShortVariable04.ShortVarialbe00, tc2.ShortVariable04.ShortVarialbe00);
         }
 
+        [TestMethod]
+        public void T32_ReadAndWriteNestedClass()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            TestClassWithNestedClass tc = new TestClassWithNestedClass
+            {
+                BitVariable00 = true,
+                BitVariable01 = new TestClassInnerWithBool { BitVariable00 = true },
+                ByteVariable02 = new TestClassInnerWithByte { ByteVariable00 = 128 },
+                BitVariable03 = true,
+                ShortVariable04 = new TestClassInnerWithShort { ShortVarialbe00 = -15000 }
+            };
+
+            plc.WriteClass(tc, DB4);
+            TestClassWithNestedClass tc2 = new TestClassWithNestedClass();
+            // Values that are read from a class are stored inside the class itself, that is passed by reference
+            plc.ReadClass(tc2, DB4);
+            Assert.AreEqual(tc.BitVariable00, tc2.BitVariable00);
+            Assert.AreEqual(tc.BitVariable01.BitVariable00, tc2.BitVariable01.BitVariable00);
+            Assert.AreEqual(tc.ByteVariable02.ByteVariable00, tc2.ByteVariable02.ByteVariable00);
+            Assert.AreEqual(tc.BitVariable03, tc2.BitVariable03);
+            Assert.AreEqual(tc.ShortVariable04.ShortVarialbe00, tc2.ShortVariable04.ShortVarialbe00);
+        }
+
         [TestMethod, ExpectedException(typeof(PlcException))]
         public void T18_ReadStructThrowsIfPlcIsNotConnected()
         {
diff --git a/S7.Net/PlcAsynchronous.cs b/S7.Net/PlcAsynchronous.cs
index f3457ae..1c28503 100644
--- a/S7.Net/PlcAsynchronous.cs
+++ b/S7.Net/PlcAsynchronous.cs
@@ -370,8 +370,9 @@ namespace S7.Net
         /// <returns>A task that represents the asynchronous write operation.</returns>
         public async Task WriteClassAsync(object classValue, int db, int startByteAdr = 0)
         {
-            var bytes = Types.Class.ToBytes(classValue).ToList();
-            await WriteBytesAsync(DataType.DataBlock, db, startByteAdr, bytes.ToArray());
+            byte[] bytes = new byte[(int)Class.GetClassSize(classValue)];
+            Types.Class.ToBytes(classValue, bytes);
+            await WriteBytesAsync(DataType.DataBlock, db, startByteAdr, bytes);
         }
 
         private async Task<byte[]> ReadBytesWithSingleRequestAsync(DataType dataType, int db, int startByteAdr, int count)
diff --git a/S7.Net/Types/Class.cs b/S7.Net/Types/Class.cs
index c1dc14f..227a521 100644
--- a/S7.Net/Types/Class.cs
+++ b/S7.Net/Types/Class.cs
@@ -239,7 +239,7 @@ namespace S7.Net.Types
             return numBytes;
         }
 
-        private static void ToBytes(object propertyValue, byte[] bytes, ref double numBytes)
+        private static double SetBytesFromProperty(object propertyValue, byte[] bytes, double numBytes)
         {
             int bytePos = 0;
             int bitPos = 0;
@@ -282,7 +282,7 @@ namespace S7.Net.Types
                     bytes2 = Single.ToByteArray((float)propertyValue);
                     break;
                 default:
-                    bytes2 = ToBytes(propertyValue);
+                    numBytes = ToBytes(propertyValue, bytes, numBytes);
                     break;
             }
 
@@ -297,6 +297,8 @@ namespace S7.Net.Types
                     bytes[bytePos + bCnt] = bytes2[bCnt];
                 numBytes += bytes2.Length;
             }
+
+            return numBytes;
         }
 
         /// <summary>
@@ -304,12 +306,8 @@ namespace S7.Net.Types
         /// </summary>
         /// <param name="sourceClass">The struct object</param>
         /// <returns>A byte array or null if fails.</returns>
-        public static byte[] ToBytes(object sourceClass)
+        public static double ToBytes(object sourceClass, byte[] bytes, double numBytes = 0.0)
         {
-            int size = (int)GetClassSize(sourceClass);
-            byte[] bytes = new byte[size];
-            double numBytes = 0.0;
-
             var properties = GetAccessableProperties(sourceClass.GetType());
             foreach (var property in properties)
             {
@@ -319,15 +317,15 @@ namespace S7.Net.Types
                     Type elementType = property.PropertyType.GetElementType();
                     for (int i = 0; i < array.Length && numBytes < bytes.Length; i++)
                     {
-                        ToBytes(array.GetValue(i), bytes, ref numBytes);
+                        numBytes = SetBytesFromProperty(array.GetValue(i), bytes, numBytes);
                     }
                 }
                 else
                 {
-                    ToBytes(property.GetValue(sourceClass, null), bytes, ref numBytes);
+                    numBytes = SetBytesFromProperty(property.GetValue(sourceClass, null), bytes, numBytes);
                 }
             }
-            return bytes;
+            return numBytes;
         }
     }
 }