Trying to not freeze UI using async / await

Question

I am trying not to freeze UI.

I used async / await, but it occurs InvalidOperationException, other thread owned this function. (I translated in english so it might be strange sentence)

public async void MimSetHeight(int _id, double _value)
{
   int index;
   index = Mim.FindIndex(mim => mim.ID == _id);
   if(mim.Count > index)
   {
      mim[index].ShapeHeight = _value;
      await Task.Delay(1000);
      mim[index].Shape.Height = _value; // <- Exception occurs
   }
}

switch(receivePacket.Data[1])
{
   case 53:
      Application.Current.Dispatcher.Invoke( () => 
           mim.MimSetHeight(5, Convert.ToInt32(Encoding.Default.GetString(receivePacket.Data))));
})));
}

I am feeling i should use Dispatcher.Invoke in last sentence.

Are there any other solution?