I am trying to upload files to Azure Blob Storage and after successful upload adding the filename to a list for my further operation. When i am doing synchronous it works fine but when i am doing async the error occured. Error : Collection was modified; enumeration operation may not execute.

foreach(var file in files)
{
   // .....
   await blockBlob.UploadFromStreamAsync(fs);
   listOfMovedLabelFiles.Add(fileName);
}
if (listOfMovedLabelFiles.Count > 0) // error point
{
    // my code for further operation
}

Is there any way to wait till all the async operations get completed.