Реализовать Stream.CopyTo() для .NET 3.5

public void CopyTo(Stream destination)

private void InternalCopyTo(Stream destination, int bufferSize)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Globalization;
 
namespace ExtentionMethods
{
    class ExtentionMethods
    {        
        public void CopyTo(Stream destination)
        {
            if (destination == null)
            {
                throw new ArgumentNullException("destination");
            }
            if (!this.CanRead && !this.CanWrite)
            {
                throw new ObjectDisposedException(null, Environment.GetResourceString("ObjectDisposed_StreamClosed"));
            }
            if (!destination.CanRead && !destination.CanWrite)
            {
                throw new ObjectDisposedException("destination", Environment.GetResourceString("ObjectDisposed_StreamClosed"));
            }
            if (!this.CanRead)
            {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnreadableStream"));
            }
            if (!destination.CanWrite)
            {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnwritableStream"));
            }
            this.InternalCopyTo(destination, 0x14000);
        }
 
        private void InternalCopyTo(Stream destination, int bufferSize)
        {
            int num;
            byte[] buffer = new byte[bufferSize];
            while ((num = this.Read(buffer, 0, buffer.Length)) != 0)
            {
                destination.Write(buffer, 0, num);
            }
        }
    }
}

using ExtentionMethods;

public byte[] ReadFully()
{
    var buffer = new MemoryStream();
    CopyTo(buffer);
    return buffer.ToArray();
}

this.CopyTo(buffer);

Unhandled Exception: System.Reflection.ReflectionTypeLoadException: The classes in the module cannot be loaded.
  at (wrapper managed-to-native) System.Reflection.Assembly:GetTypes (bool)
  at System.Reflection.Assembly.GetTypes () [0x00000] in <filename unknown>:0 
  at Mono.CSharp.RootNamespace.ComputeNamespaces (System.Reflection.Assembly assembly, System.Type extensionType) [0x00000] in <filename unknown>:0 
  at Mono.CSharp.RootNamespace.ComputeNamespace (Mono.CSharp.CompilerContext ctx, System.Type extensionType) [0x00000] in <filename unknown>:0 
  at Mono.CSharp.GlobalRootNamespace.ComputeNamespaces (Mono.CSharp.CompilerContext ctx) [0x00000] in <filename unknown>:0 
  at Mono.CSharp.Driver.LoadReferences () [0x00000] in <filename unknown>:0 
  at Mono.CSharp.Driver.Compile () [0x00000] in <filename unknown>:0 
  at Mono.CSharp.Driver.Main (System.String[] args) [0x00000] in <filename unknown>:0 
 
Missing method .ctor in assembly E:\Users\Unity3D\Parsing\Assets\Plugins\AndroidXml.dll, type System.Runtime.Versioning.TargetFrameworkAttribute
The class System.Runtime.Versioning.TargetFrameworkAttribute could not be loaded, used in AndroidXml
Can't find custom attr constructor image: E:\Users\Unity3D\Parsing\Assets\Plugins\AndroidXml.dll mtoken: 0x0a00000e

var reader = new AndroidXmlReader(stream);
XDocument doc = XDocument.Load(reader);

string fileContent; // Содержимое файла AndroidManifest.xml (в виде строки)
byte[] fileContentBytes; // Содержимое файла AndroidManifest.xml (в виде массива байтов)
// Чтение содержимого файла AndroidManifest.xml
using (WWW www = new WWW(filePath + "AndroidManifest.xml"))
{
    yield return www;
    fileContent = www.text;
    fileContentBytes = www.bytes;
}

#if UNITY_EDITOR
XDocument doc = XDocument.Parse(fileContent);
#else
var reader = new AndroidXmlReader(fileContentBytes);
XDocument doc = XDocument.Load(reader);
#endif

Stream stream = new MemoryStream(byteArray);

Stream stream = new MemoryStream(fileContentBytes);
var reader = new AndroidXmlReader(stream);
XDocument doc = XDocument.Load(reader);