diff --git a/src/SharpCompress/Archives/Rar/RarArchive.cs b/src/SharpCompress/Archives/Rar/RarArchive.cs
index fb052c37..52ffaa1c 100644
--- a/src/SharpCompress/Archives/Rar/RarArchive.cs
+++ b/src/SharpCompress/Archives/Rar/RarArchive.cs
@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
diff --git a/src/SharpCompress/Archives/Rar/RarArchiveEntry.cs b/src/SharpCompress/Archives/Rar/RarArchiveEntry.cs
index 60ece4ee..3f2360b2 100644
--- a/src/SharpCompress/Archives/Rar/RarArchiveEntry.cs
+++ b/src/SharpCompress/Archives/Rar/RarArchiveEntry.cs
@@ -24,7 +24,7 @@ namespace SharpCompress.Archives.Rar
 
         public IArchive Archive => archive;
 
-        internal override IEnumerable<FilePart> Parts => this.parts;
+        internal override IEnumerable<FilePart> Parts => parts.Cast<FilePart>();
 
         internal override FileHeader FileHeader => parts.First().FileHeader;
 
diff --git a/src/SharpCompress/Compressors/Rar/UnpackV2017/FragmentedWindow.unpack50frag_cpp.cs b/src/SharpCompress/Compressors/Rar/UnpackV2017/FragmentedWindow.unpack50frag_cpp.cs
index b0bc6da7..cd0b5eb0 100644
--- a/src/SharpCompress/Compressors/Rar/UnpackV2017/FragmentedWindow.unpack50frag_cpp.cs
+++ b/src/SharpCompress/Compressors/Rar/UnpackV2017/FragmentedWindow.unpack50frag_cpp.cs
@@ -10,10 +10,6 @@ using size_t = System.UInt64;
 using int64 = System.Int64;
 
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace SharpCompress.Compressors.Rar.UnpackV2017
 {
diff --git a/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.unpack50_cpp.cs b/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.unpack50_cpp.cs
index 3a0d63c5..53f0e713 100644
--- a/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.unpack50_cpp.cs
+++ b/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.unpack50_cpp.cs
@@ -334,7 +334,7 @@ void UnpWriteBuf()
               FragWindow.CopyData(Mem,0,BlockStart,BlockLength);
             else
               //x memcpy(Mem,Window+BlockStart,BlockLength);
-              Array.Copy(Window, BlockStart, Mem, 0, BlockLength);
+              Utility.Copy(Window, BlockStart, Mem, 0, BlockLength);
           }
           else
           {
@@ -347,9 +347,9 @@ void UnpWriteBuf()
             else
             {
               //x memcpy(Mem,Window+BlockStart,FirstPartLength);
-              Array.Copy(Window, BlockStart, Mem, 0, FirstPartLength);
+              Utility.Copy(Window, BlockStart, Mem, 0, FirstPartLength);
               //x memcpy(Mem+FirstPartLength,Window,BlockEnd);
-              Array.Copy(Window, 0, Mem, FirstPartLength,BlockEnd);
+              Utility.Copy(Window, 0, Mem, FirstPartLength,BlockEnd);
             }
           }
 
diff --git a/src/SharpCompress/Lazy.cs b/src/SharpCompress/Lazy.cs
new file mode 100644
index 00000000..893e3bb1
--- /dev/null
+++ b/src/SharpCompress/Lazy.cs
@@ -0,0 +1,29 @@
+using System;
+
+namespace SharpCompress
+{
+    public class Lazy<T>
+    {
+        private readonly Func<T> _lazyFunc;
+        private bool _evaluated;
+        private T _value;
+        
+        public Lazy(Func<T> lazyFunc)
+        {
+            _lazyFunc = lazyFunc;
+        }
+
+        public T Value
+        {
+            get
+            {
+                if (!_evaluated)
+                {
+                    _value = _lazyFunc();
+                    _evaluated = true;
+                }
+                return _value;
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/SharpCompress/Readers/Rar/RarReader.cs b/src/SharpCompress/Readers/Rar/RarReader.cs
index 05fe0daa..23a4005e 100644
--- a/src/SharpCompress/Readers/Rar/RarReader.cs
+++ b/src/SharpCompress/Readers/Rar/RarReader.cs
@@ -1,5 +1,4 @@
-using System;
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using SharpCompress.Common;
diff --git a/src/SharpCompress/SharpCompress.csproj b/src/SharpCompress/SharpCompress.csproj
index a20a92a9..5c1d0815 100644
--- a/src/SharpCompress/SharpCompress.csproj
+++ b/src/SharpCompress/SharpCompress.csproj
@@ -6,7 +6,7 @@
     <AssemblyVersion>0.20.0</AssemblyVersion>
     <FileVersion>0.20.0</FileVersion>
     <Authors>Adam Hathcock</Authors>
-    <TargetFrameworks Condition="'$(LibraryFrameworks)'==''">netstandard2.0</TargetFrameworks>
+    <TargetFrameworks Condition="'$(LibraryFrameworks)'==''">net45;net35;netstandard1.0;netstandard1.3;netstandard2.0</TargetFrameworks>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <AssemblyName>SharpCompress</AssemblyName>
diff --git a/src/SharpCompress/Utility.cs b/src/SharpCompress/Utility.cs
index bca28a9d..e97d093d 100644
--- a/src/SharpCompress/Utility.cs
+++ b/src/SharpCompress/Utility.cs
@@ -184,6 +184,18 @@ namespace SharpCompress
                 action(item);
             }
         }
+        
+        public static void Copy(Array sourceArray, long sourceIndex, Array destinationArray, long destinationIndex, long length)
+        {
+            if (sourceIndex > Int32.MaxValue || sourceIndex < Int32.MinValue)
+                throw new ArgumentOutOfRangeException();
+            if (destinationIndex > Int32.MaxValue || destinationIndex < Int32.MinValue)
+                throw new ArgumentOutOfRangeException();
+            if (length > Int32.MaxValue || length < Int32.MinValue)
+                throw new ArgumentOutOfRangeException();
+
+            Array.Copy(sourceArray, (int)sourceIndex, destinationArray, (int)destinationIndex, (int)length);
+        }
 
         public static IEnumerable<T> AsEnumerable<T>(this T item)
         {