Do I need to reset a stream(C#) back to the start?

Question

Hi

I don't know too much about streams in C#. Right now I have a stream that I put into a stream reader and read it. Later on in some other method I need to read the stream(same stream object) but this time I get this error

System.ArgumentException was unhandled by user code
  Message="Stream was not readable."
  Source="mscorlib"
  StackTrace:
       at System.IO.StreamReader..ctor(Stream stream, Encoding encoding, Boolean detectEncodingFromByteOrderMarks, Int32 bufferSize)
       at System.IO.StreamReader..ctor(Stream stream)
       at ExtractTitle(Stream file) in :line 33
       at GrabWebPage(String webPath) in :line 62
       at lambda_method(ExecutionScope , ControllerBase , Object[] )
       at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
       at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
       at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
       at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClassa.<InvokeActionMethodWithFilters>b__7()
       at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
  InnerException:

So I am thinking maybe by reading the stream it goes to the end. Then when I try to read it again it is at the end of the stream and thats why I am getting this error.

So can anyone shed some light on this?

Thanks

Answer 1

When you read a stream to the end, specifically with StreamReader's ReadToEnd method, you have to Seek it back to the beginning. This can be done like so:

StreamReader sr = new StreamReader(stream);
sr.ReadToEnd();
sr.Seek(0, SeekOrigin.Begin);
sr.ReadToEnd(); // This now works

Answer 2

Your conclusion is correct; once you've reached the end of your stream, you won't be able to read more data until you've reset your position within the stream:

myStream.Position = 0;

This is equivalent to seeking back to the beginning. Note that your stream must support seeking for this to work; not all streams do. You can check this with the CanSeek property.