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Fastest way to access data from a file. Messages   Related Types This message was discovered on microsoft.public.dotnet.languages.csharp. Post a new message to this list... Ignacio X. Domínguez Hi. I'm developing a desktop application that needs to store some data in a local file. Let's say for example that I want to have an address book with names and phone numbers in a file. I would like to be able to retrieve the name by searching for a given phone number the fastest I can. I have considered the posibility of using XmlTextReader with something like: <list> <item number="1234567"> <name>John Doe</name> </item> <item number="9876*"> <name>Jane Doe</name> </item> </list> or a simple text file with entries separated by special characters: 1234567~John Doe%9876*~Jane Doe% and then use Split("%".ToCharArray()) to get an array of items, and then Split("~".ToCharArray()) on every item to get name and number. I this database will have around 200 entries (name and number in this example), so I would like to know which one do you think will perform faster and better on most configurations. Thank you in advance. Ignacio X. Domínguez Reply to this message...        Dennis Myrén I would recommend an XML approach. If the data file is not estimated to be gigantic, I would use a DOM approach (XmlDocument). Than you can perform XPath evaluations, which are fast if they are used efficiently, to find specific records. And the data file also makes great sense when viewing in a text editor, which may be good for debugging/monitoring the data easily. -- Regards, Dennis JD Myrén Oslo Kodebureau "Ignacio X. Domínguez" <Click here to reveal e-mail address> wrote in message news:%Click here to reveal e-mail address... > Hi. I'm developing a desktop application that needs to store some data in a [Original message clipped] Reply to this message...        Ignacio X. Domínguez Hi Dennis, [Original message clipped] I would have around 200 entries in average, in some cases maybe twice that number. Do you think using XmlDocument in this case is better than using XmlTextReader? or viceversa? Does these load the entire XML file into memory? [Original message clipped] What is the most efficient way of using it? Thanks in advance. "Dennis Myrén" <Click here to reveal e-mail address> wrote in message news:O7x1d.9404$g%Click here to reveal e-mail address... [Original message clipped] Reply to this message...        Dennis Myrén >I would have around 200 entries in average 200 entries is just about no trouble for the DOM to parse very fast. Actually, you could have a lot more than that using DOM as well. >Does these load the entire XML file into memory? The DOM(XmlDocument) implementation loads the data into memory, whereas the XmlReader(XmlTextReader) does not. However I do not think that is a problem here. >What is the most efficient way of using it? Basically just try to avoid the wildcard(*) in XPath evaluations. This is my recommendation, assuming the XML look like this: <list> <item number="1234567"> <name>John Doe</name> </item> <item number="9876543"> <name>Jane Doe</name> </item> </list> <snippet> string filename = "C:\phonenumbers.xml", phonenumber = "1234567"; XmlDocument doc = new XmlDocument(); doc.Load(filename); // Select the node. XmlNode resultNode = doc.DocumentElement.SelectSingleNode (string.Format("item[@number='{0}']", phonenumber)); // Now we have all information about the item in the resultNode instance. if (null != resultNode) Console.WriteLine("Phone number {0} belongs to {1}!" , phonenumber, resultNode.SelectSingleNode("name").InnerText); else Console.WriteLine("Could not find phone number number {0}.", ssn); </snippet> -- Regards, Dennis JD Myrén Oslo Kodebureau "Ignacio X. Domínguez" <Click here to reveal e-mail address> wrote in message news:%23k$%Click here to reveal e-mail address... [Original message clipped] Reply to this message...        Ignacio X. Domínguez I was thinking in something like this: <phonebook> <item number="1234567">John Doe</item> <item number="7654321">Jane Doe</item> </phonebook> I tried the following code and worked, but not sure if it is the most efficient way: GetNameFromNumber(string number) { System.Xml.XmlTextReader XMLReader = new System.Xml.XmlTextReader("PhoneBook.xml"); XMLReader.MoveToContent(); while(XMLReader.Read() { XMLReader.MoveToContent(); string thisnum = XMLReader.GetAttribute("number"); if(thisnum != null && thisnum == number) { return XMLReader.ReadString(); } } return null; } What do you think? "Dennis Myrén" <Click here to reveal e-mail address> wrote in message news:2DC1d.9451$g%Click here to reveal e-mail address... [Original message clipped] Reply to this message...        Dennis Myrén Yes, if you insist on using the XmlReader, that looks good. Just remember that if you use XmlReader, invoke Close() prior to return from the function, otherwise the file channel remains open. If it is likely the function will be called frequently, then maybe you should think of either having a file channel open or load the data at startup maybe into some array of a custom struct, for best performance possible). struct Item { string number, name; } -- Regards, Dennis JD Myrén Oslo Kodebureau "Ignacio X. Domínguez" <Click here to reveal e-mail address> wrote in message news:%Click here to reveal e-mail address... [Original message clipped] Reply to this message...        Ignacio Machin \( .NET/ C# MVP \) Hi, That should make a small file, so I will concentrate myself instead on which is the most convenient method to make searches/insertions, etc in the code. In any way you should read all that data in memory. cheers, -- Ignacio Machin, ignacio.machin AT dot.state.fl.us Florida Department Of Transportation "Ignacio X. Domínguez" <Click here to reveal e-mail address> wrote in message news:%23k$%Click here to reveal e-mail address... [Original message clipped] Reply to this message...        Ignacio Machin \( .NET/ C# MVP \) Hi tocayo :) The fastest way is to having it in memory, you could create a struct with two members ( name, number) and have an ArrayList of them.. you read them at the beggining and after that all is from memory. if for some reason you cannot have them in memory the best way would be keeping a text file, not a XML, in the text file you keep one record per line, and divide the fields using a special char. For further performance you should put the field you will search for first and make it a fixed length. in this way you can use String.SubString instead of String.Split Ayway , the best way is to keep them all in memory. even so I think that the XML is not very good idea here. Cheers, -- Ignacio Machin, ignacio.machin AT dot.state.fl.us Florida Department Of Transportation "Ignacio X. Domínguez" <Click here to reveal e-mail address> wrote in message news:%Click here to reveal e-mail address... > Hi. I'm developing a desktop application that needs to store some data in a [Original message clipped] Reply to this message...        Ignacio X. Domínguez Hi tocayo (hehehe), Why do you think a simple text file is better than a XML in this case? The problem I see with the text file is the special separator character, because it is going to limit somehow what the strings in each entry can contain (can't have that char). Therefore, I need to make sure in code that the strings being stored in the text file never contain that character. I know I can use any weird character making it unlikely that it will be chosen by any user, but there is still a chance. What are your thoughts about this? "Ignacio Machin ( .NET/ C# MVP )" <ignacio.machin AT dot.state.fl.us> wrote in message news:Click here to reveal e-mail address... [Original message clipped] Reply to this message...        Ignacio Machin \( .NET/ C# MVP \) Hi, If you use a text file, y "Ignacio X. Domínguez" <Click here to reveal e-mail address> wrote in message news:eK%Click here to reveal e-mail address... > Hi tocayo (hehehe), Why do you think a simple text file is better than a XML > in this case? It's simpler, and faster than the XML approach. With XML you have to deal with building queries, etc, and searching data is not as easy. you have to create objects for each queries, etc. The problem I see with the text file is the special separator [Original message clipped] No at all, if you use a comma you will get this problem , if you use a control char you will not have it, I have a similar approach in a pocketPC app and I use char(20), therefore I dont have the problem of the separator char happening in a field. a simple String.Split and it's done. then you can use something like a hashtable and use the number ( or names) as index for the other value, very easy, efficient and the code is cleaner. Cheers, -- Ignacio Machin, ignacio.machin AT dot.state.fl.us Florida Department Of Transportation Reply to this message...     System.Collections.ArrayList System.Console System.String System.Xml.XmlDocument System.Xml.XmlNode System.Xml.XmlReader System.Xml.XmlTextReader Ad MBR BootFX Best-of-breed application framework for .NET projects, developed by Matthew Baxter-Reynolds and MBR IT

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