C# convert Bytearray to System.Draw.Image

Hello,

I need to convert a Byte array back into an image. If I do that in the Unity IDE it is working but if I do it after I compiled it in windows it is not working anymore. I am converting the Byte array into a Stream and try to convert the Stream into an image afterwards.

 Stream tempstream;
 System.Drawing.Image tempimage = null;
 try{
             Byte[] ba;
             ba = (Byte[]) reader["FlagPng"];
             Debug.Log ("ByteArray: "+ba.ToString ());
             tempstream = new MemoryStream(ba);
             Debug.Log ("tempstream: "+tempstream.ToString ());
             tempimage = Image.FromStream(tempstream);
         }
         catch(Exception ex){
                 Debug.LogError ("Errormessage 100: \n "+ex.Message );
                 Debug.LogError ("Errorsource 100: \n "+ex.Source );
                 Debug.LogError ("Errorstacktrace 100: \n "+ex.StackTrace);
                 Debug.LogError ("Errortargetsite 100: \n "+ex.TargetSite);
                 
                 
         }

In my output_log is written: ByteArray: System.Byte[]

tempstream: System.IO.MemoryStream

Errormessage 100: Could not load type 'System.IO.InternalBufferOverflowException' from assembly 'System.Drawing'.

Errorsource 100: System.Drawing

Errorstacktrace 100: at System.Drawing.Image.InitFromStream (System.IO.Stream stream) [0x00000] in :0

at System.Drawing.Image.LoadFromStream (System.IO.Stream stream, Boolean keepAlive) [0x00000] in :0

at System.Drawing.Image.FromStream (System.IO.Stream stream) [0x00000] in :0

at SQLDatabase.ReadTblLanguages () [0x00000] in :0

Errortargetsite 100: IntPtr InitFromStream(System.IO.Stream)

I can tell that the problem should be the line: tempimage = Image.FromStream(tempstream);

All dlls I am using are mono dlls from the library directory of Unity.

Can anyone tell me how I can convert a stream into an image in Unity?

Thank you in advance.