DeflateStream & MemoryStream?
in [CSharp]
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From: Asaf on 23 Feb 2006 14:51 Hi, I am trying to Compress & Decompress a DataSet. When running this code I am receiving the error: System.Xml.XmlException was unhandled Message="Root element is missing." Source="System.Xml" The code: DataSet dsDataOrginal = new DataSet(); DataSet dsDataAfterDecompress = new DataSet(); dsDataOrginal.ReadXml(@"C:\VSProjects2005\ZIP_Compress\TheXML.XML"); //Compressing to Memory MemoryStream MS = new MemoryStream(); DeflateStream dfs = new DeflateStream(MS, CompressionMode.Compress, false); dsDataOrginal.WriteXml(ms, XmlWriteMode.WriteSchema); //DeCompressing from Memory MS.Position = 0; DeflateStream dfsDecompress = new DeflateStream(MS, CompressionMode.Decompress, false); dsAfterDecompress.ReadXml(MS); Thanks for any help, Asaf
From: Jon Skeet [C# MVP] on 24 Feb 2006 02:15 Asaf <AG70(a)newsgroups.nospam> wrote: > I am trying to Compress & Decompress a DataSet. > When running this code I am receiving the error: > > System.Xml.XmlException was unhandled > Message="Root element is missing." > Source="System.Xml" > > The code: > > DataSet dsDataOrginal = new DataSet(); > DataSet dsDataAfterDecompress = new DataSet(); > > > dsDataOrginal.ReadXml(@"C:\VSProjects2005\ZIP_Compress\TheXML.XML"); > > //Compressing to Memory > MemoryStream MS = new MemoryStream(); > DeflateStream dfs = new DeflateStream(MS, > CompressionMode.Compress, false); > dsDataOrginal.WriteXml(ms, XmlWriteMode.WriteSchema); > > //DeCompressing from Memory > MS.Position = 0; > DeflateStream dfsDecompress = new DeflateStream(MS, > CompressionMode.Decompress, false); > dsAfterDecompress.ReadXml(MS); You're never using the deflating or inflating streams. You should be calling WriteXml (dfs, XmlWriteMode.WriteSchema). You should then Flush dfs before using the MemoryStream. After that, you should be able to call ReadXml but with dfsDecompress rather than MS. I'm slightly concerned that without having closed the DeflateStream to start with, there may be problems. You may need to close dfs instead of just flushing it, then create a new MemoryStream with the byte array from the first MemoryStream, just so it knows where it ends properly. -- Jon Skeet - <skeet(a)pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too
From: Asaf on 24 Feb 2006 03:36 Hi Peter, Hi Jon, Thanks for your reply. Let's start again :-) The code below is working fine when using FileStream: //Compress to and save the file to disk FileStream msf = new FileStream(@"C:\VSProjects2005\ZIP_Compress\TheXML.xmd", FileMode.Create, FileAccess.Write); dfs = new DeflateStream(msf, CompressionMode.Compress, false); dsOrginal.WriteXml(dfs); dfs.Close(); msf.Close(); MessageBox.Show("Compress to file, Done!"); //Read Compressed file from disk, decompress data and show rows count for dataset FileStream infile = new FileStream(@"C:\VSProjects2005\ZIP_Compress\TheXML.xmd", FileMode.Open, FileAccess.Read); DeflateStream DefStream = new DeflateStream(infile, CompressionMode.Decompress, false); dsAfterDecompress.ReadXml(DefStream); infile.Close(); textBox1.Text = dsAfterDecompress.Tables[0].Rows.Count.ToString(); Same code but using MemoryStream does not work: DataSet dsDataOrginal = new DataSet(); DataSet dsDataAfterDecompress = new DataSet(); dsDataOrginal.ReadXml(@"C:\VSProjects2005\ZIP_Compress\TheXML.XML"); //Compressing to Memory MemoryStream MS = new MemoryStream(); DeflateStream dfs = new DeflateStream(MS, CompressionMode.Compress, false); dsDataOrginal.WriteXml(dfs); dfs.Close(); //DeCompressing from Memory DeflateStream dfsDecompress = new DeflateStream(MS, CompressionMode.Decompress, false); dsAfterDecompress.ReadXml(dfsDecompress); textBox1.Text = dsAfterDecompress.Tables[0].Rows.Count.ToString(); If using dfs.Close(); then I am getting the error: "The base stream is not readable. Parameter name: stream" If dfs.Close(); is omitted then I am getting the error: "Root element is missing" when trying to do: dsAfterDecompress.ReadXml(dfsDecompress); my guess is because the Stream is at the end Position but Position property can't be use with DeflateStream so I can't rewind the DeflateStream to zero position before doing dsAfterDecompress.ReadXml(dfsDecompress); Help Please! Regards, Asaf "Jon Skeet [C# MVP]" wrote: > Asaf <AG70(a)newsgroups.nospam> wrote: > > I am trying to Compress & Decompress a DataSet. > > When running this code I am receiving the error: > > > > System.Xml.XmlException was unhandled > > Message="Root element is missing." > > Source="System.Xml" > > > > The code: > > > > DataSet dsDataOrginal = new DataSet(); > > DataSet dsDataAfterDecompress = new DataSet(); > > > > > > dsDataOrginal.ReadXml(@"C:\VSProjects2005\ZIP_Compress\TheXML.XML"); > > > > //Compressing to Memory > > MemoryStream MS = new MemoryStream(); > > DeflateStream dfs = new DeflateStream(MS, > > CompressionMode.Compress, false); > > dsDataOrginal.WriteXml(ms, XmlWriteMode.WriteSchema); > > > > //DeCompressing from Memory > > MS.Position = 0; > > DeflateStream dfsDecompress = new DeflateStream(MS, > > CompressionMode.Decompress, false); > > dsAfterDecompress.ReadXml(MS); > > You're never using the deflating or inflating streams. You should be > calling > WriteXml (dfs, XmlWriteMode.WriteSchema). > > You should then Flush dfs before using the MemoryStream. After that, > you should be able to call ReadXml but with dfsDecompress rather than > MS. > > I'm slightly concerned that without having closed the DeflateStream to > start with, there may be problems. You may need to close dfs instead of > just flushing it, then create a new MemoryStream with the byte array > from the first MemoryStream, just so it knows where it ends properly. > > -- > Jon Skeet - <skeet(a)pobox.com> > http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet > If replying to the group, please do not mail me too >
From: Marc Gravell on 24 Feb 2006 04:02 In the file code you use two separate streams, which means the position is effictively reset between the two methods; in the second block you are using a single stream, but are *not* resetting the position. Just set Position = 0 before trying to read what you have written Marc
From: Asaf on 24 Feb 2006 04:31
Hi Marc, Position property of DeflateStream cannot be set. Regards, Asaf "Marc Gravell" wrote: > In the file code you use two separate streams, which means the position is > effictively reset between the two methods; in the second block you are using > a single stream, but are *not* resetting the position. > > Just set Position = 0 before trying to read what you have written > > Marc > > > |