I can't to download file from SGuite

I can’t download file from my box
I am using this code

Try {
Byte allBytes = New Byte[item.ContentStream.Length];
int bytesRead = item.ContentStream.Read(allBytes, 0, (int)item.ContentStream.Length);

String destinationFile = Path.GetFullPath(".")+"\Input\" + num.Next().ToString() +" - "+ item.Name;
Console.WriteLine(destinationFile);
BinaryWriter writer = New BinaryWriter(New FileStream(destinationFile, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None));
writer.Write(allBytes);
writer.Close();
} Catch (Exception e) {
Console.WriteLine(e.Message);
}

but it not work, i have got this erreur

image

thank you in advance