两次读取file.inputstream

Question

I need to read csv file twice. but after first reading:

using (var csvReader = new StreamReader(file.InputStream))
{
    fileFullText += csvReader.ReadToEnd();
    file.InputStream.Seek(0, SeekOrigin.Begin);
    csvReader.Close();
}

using file in enother function:

public static List<string> ParceCsv(HttpPostedFileBase file)
{
    //file.InputStream.Seek(0, SeekOrigin.Begin);
    using (var csvReader = new StreamReader(file.InputStream))
    {
       // csvReader.DiscardBufferedData();
       // csvReader.BaseStream.Seek(0, SeekOrigin.Begin);
        string inputLine = "";
        var values = new List<string>();

        while ((inputLine = csvReader.ReadLine()) != null)
        {
            values.Add(inputLine.Trim().Replace(",", "").Replace(" ", ""));
        }
        csvReader.Close();
        return values;
    } 
}

The file.Length is 0. Can anybody help?

Answer 1

The reason is that SteramReader 's Dispose() method also closes the underlying stream; In your case file.InputStream . The using statement calls Dispose() implicitly. Try to replace using with disposes of both your StreamReaded -s after you finished both read operations. As I remember some stream classes have a bool option to leave underlying stream open after dispose.

.NET 4.5 fixed this issue by introducing leaveOpen parameter in SteamReader constructor. See: MSDN

public StreamReader(
    Stream stream,
    Encoding encoding,
    bool detectEncodingFromByteOrderMarks,
    int bufferSize,
    bool leaveOpen
)

One more thing. You do not need to close SteramReader yourself (the line with csvReader.Close(); ) when you wrap it in using statement, thus Dispose() and Close() are the same in case of StreamReader .

Answer 2

if your using HttpPostedFileBase you need to clone it first,
use the code this git here
or just add this as a class in your namespace:

public static class HttpPostedFileBaseExtensions
{
    public static Byte[] ToByteArray(this HttpPostedFileBase value)
    {
        if (value == null)
            return null;
        var array = new Byte[value.ContentLength];
        value.InputStream.Position = 0;
        value.InputStream.Read(array, 0, value.ContentLength);
        return array;
    }
}

now you can read the HttpPostedFileBase like so:

private static void doSomeStuff(HttpPostedFileBase file)
{
    try
    {
        using (var reader = new MemoryStream(file.ToByteArray()))
        {
            // do some stuff... say read it to xml
            using (var xmlTextReader = new XmlTextReader(reader))
            {                    

            }
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

after using this you can still write in your main code:

file.SaveAs(path);

and it will save it to the file.