StreamReaderExtension.cs

using System.IO;
using System.Text;

public static class StreamExtensions
{
    public static string ToEncodedString(this Stream stream, Encoding enc = null)
    {
        enc = enc ?? Encoding.UTF8;

        byte[] bytes = new byte[stream.Length];
        stream.Position = 0;
        stream.Read(bytes, 0, (int)stream.Length);
        string data = enc.GetString(bytes);
        return data;
    }
}