c# - How to download memorystream to a file?

Question

I'm using the below sample code for writing and downloading a memory stream to a file in C#.

MemoryStream memoryStream = new MemoryStream();
TextWriter textWriter = new StreamWriter(memoryStream);
textWriter.WriteLine("Something");           
byte[] bytesInStream = new byte[memoryStream.Length];
memoryStream.Write(bytesInStream, 0, bytesInStream.Length);
memoryStream.Close();          
Response.Clear();
Response.ContentType = "application/force-download";
Response.AddHeader("content-disposition",
                   "attachment; filename=name_you_file.xls");
Response.BinaryWrite(bytesInStream);
Response.End();

I am getting the following error:

Specified argument was out of the range of valid values.
Parameter name: offset

What may be the cause?

Answer 1

At the point in your code where you copy the data to an array, the TextWriter might not have flushed the data. This will happen when you Flush() or when you Close() it.

See if this works:

MemoryStream memoryStream = new MemoryStream();
TextWriter textWriter = new StreamWriter(memoryStream);
textWriter.WriteLine("Something");   
textWriter.Flush(); // added this line
byte[] bytesInStream = memoryStream.ToArray(); // simpler way of converting to array
memoryStream.Close(); 

Response.Clear();
Response.ContentType = "application/force-download";
Response.AddHeader("content-disposition", "attachment;    filename=name_you_file.xls");
Response.BinaryWrite(bytesInStream);
Response.End();