c# - fileStream.CopyTo(memoryStream)后，memoryStream为null

Question

所以，我有获取 BitmapImage 的函数，我需要将它保存到 iso 存储并转换为 Base64(用于发送到服务器)。但是，从 fileStream 复制到 memoryStream 不成功。

public void SetImage(BitmapImage bitmap)
{
    if (isoFiles.FileExists(Settings.FILE_AVATAR_JPG))
        isoFiles.DeleteFile(Settings.FILE_AVATAR_JPG);

    var fileStream = isoFiles.CreateFile(Settings.FILE_AVATAR_JPG);
    var wb = new WriteableBitmap(bitmap);
    wb.SaveJpeg(fileStream, 120, 120, 0, 85); // file is saved 

    var memoryStream = new MemoryStream();
    fileStream.CopyTo(memoryStream);          // here, memoryStream is null
    byte[] result = memoryStream.ToArray();
    fileStream.Close();

    var base64 = Convert.ToBase64String(result);
}

Answer 1

Stream.CopyTo 从 fileStream 的当前位置复制，该位置已被 SaveJpeg() 更改，因此您需要重置它；

var memoryStream = new MemoryStream();

fileStream.Position = 0;
fileStream.CopyTo(memoryStream);