[C#] Stahování více souborů najednou.

Zdravím poradňáci, žádám vás o pomoc v programovacím jazyku C#.
Potřeboval bych přes 1 tlačítko stáhnout až 10 souborů, všechny mam postupně vypsané.
Problém je v tom že hned u druhého stažení to hodí Error ve tvaru:

System.NotSupportedException was unhandled
  HResult=-2146233067
  Message=Klient WebClient nepodporuje souběžné operace vstupu a výstupu.
  Source=System
  StackTrace:
       v System.Net.WebClient.ClearWebClientState()
       v System.Net.WebClient.DownloadFileAsync(Uri address, String fileName, Object userToken)
       v System.Net.WebClient.DownloadFileAsync(Uri address, String fileName)
       v FreeLance___Genesis.Form1.onClickZahajit(Object sender, EventArgs e) v C:\Users\siOnz_000\AppData\Local\Temporary Projects\FreeLance - Genesis\Form1.cs:řádek 31
       v System.Windows.Forms.Control.OnClick(EventArgs e)
       v System.Windows.Forms.Button.OnClick(EventArgs e)
       v System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       v System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       v System.Windows.Forms.Control.WndProc(Message& m)
       v System.Windows.Forms.ButtonBase.WndProc(Message& m)
       v System.Windows.Forms.Button.WndProc(Message& m)
       v System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       v System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       v System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       v System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       v System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       v System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       v System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       v System.Windows.Forms.Application.Run(Form mainForm)
       v FreeLance___Genesis.Program.Main() v C:\Users\siOnz_000\AppData\Local\Temporary Projects\FreeLance - Genesis\Program.cs:řádek 18
       v System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       v System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       v Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       v System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       v System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       v System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       v System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       v System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

Kromě metody kterou jsem to udělal a nefunguje. Mě jiná nenapadá.

 WebClient client = new WebClient();
client.DownloadFileAsync(new Uri("bla.bar"), "bla.jar");
client.DownloadFileAsync(new Uri("bla.bar"), "bla.jar");