ESDKLib by Johannes Bildstein - Argument Exception "The delegate must have only one target"

Question

I am using Canon SDK Example of Mr. Johannes Bildstein EDSDKLib but I am getting Argument Exception with Message "The delegate must have only one target."

When I dig through I found MainThread.Invoke(() => of TakePhotoShutterAsync() method is throwing exception. Kindly advise how I can fix this.

Below is my Stack Trace

at EOSDigital.API.GeneralExceptionHandler.BeginInvoke(Object sender, Exception ex, AsyncCallback callback, Object object)
   at EOSDigital.API.ErrorHandler.ReportError(Object sender, Exception ex)
   at EOSDigital.API.Camera.<TakePhotoShutterAsync>b__80_0(Object state)
   at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()

Below is full method where I am getting exception.

/// <summary>
    /// Takes a photo with the current camera settings asynchronously with the PressShutterButton command
    /// </summary>
    /// <exception cref="ObjectDisposedException">Camera is disposed</exception>
    /// <exception cref="CameraSessionException">Session is closed</exception>
    /// <exception cref="SDKStateException">Canon SDK is not initialized</exception>
    public void TakePhotoShutterAsync()
    {
        CheckState();
        ThreadPool.QueueUserWorkItem((state) =>
        {
            try
            {
                MainThread.Invoke(() =>
                {
                    SendCommand(CameraCommand.PressShutterButton, (int)ShutterButton.Completely);
                    SendCommand(CameraCommand.PressShutterButton, (int)ShutterButton.OFF);
                });
            }
            catch (Exception ex) { err.writeError(ex.Message); if (!ErrorHandler.ReportError(this, ex)) throw; }
        });
    }