asp.net core - Trying to convert a base64String into a IFormFile throws SystemInvalidOperation exception in C#

Question

Closed. This question needs debugging details. It is not currently accepting answers. question from:https://stackoverflow.com/questions/65920854/trying-to-convert-a-base64string-into-a-iformfile-throws-systeminvalidoperation

Answer 1

You are implicitly calling Dispose on the MemoryStreams after you pass them to the FormFile constructor due to the using block. You then return a list of FormFile objects where the inner streams are all disposed.

FormFile does not make a copy of the stream's content, but instead (via ReferencedReadStream) calls methods like Stream.Read which (in the case of MemoryStream at least) will throw an exception if the stream has been closed--which it has due to Dispose.

You've not provided any information such as a stack trace so this is a best guess, but removing the using block should suffice to fix this problem.

private List<IFormFile> Base64ToImage(List<EquipmentFile> equipmentFiles)
{
    List<IFormFile> formFiles = new List<IFormFile>();
    foreach (var eqp in equipmentFiles)
    {
        
        byte[] bytes = Convert.FromBase64String(eqp.File);
        MemoryStream stream = new MemoryStream(bytes);
        
        IFormFile file = new FormFile(stream, 0, bytes.Length, eqp.Name, eqp.Name);
        formFiles.Add(file);
        
    }
    return formFiles;
}