Best way to store data locally in NET C

Question

I m writing an application that takes user data and stores it locally for use later  The application will be started and stopped fairly often  and I d like to make it save load the data on application start end   It d be fairly straightforward if I used flat files  as the data doesn t really need to be secured  it ll only be stored on this PC   The options I believe are thus    Flat files XML SQL DB   Flat files require a bit more effort to maintain  no built in classes like with XML   however I haven t used XML before  and SQL seems like overkill for this relatively easy task   Are there any other avenues worth exploring  If not  which of these is the best solution     Edit  To add a little more data to the problem  basically the only thing I d like to store is a Dictionary that looks like this  Dictionary lt string  List lt Account gt  gt     where Account is another custom type   Would I serialize the dict as the xmlroot  and then the Account type as attributes     Update 2   So it s possible to serialize a dictionary  What makes it complicated is that the value for this dict is a generic itself  which is a list of complex data structures of type Account  Each Account is fairly simple  it s just a bunch of properties   It is my understanding that the goal here is to try and end up with this    lt Username1 gt       lt Account1 gt           lt Data1 gt data1 lt  Data1 gt           lt Data2 gt data2 lt  Data2 gt       lt  Account1 gt   lt  Username1 gt   lt Username2 gt       lt Account1 gt           lt Data1 gt data1 lt  Data1 gt           lt Data2 gt data2 lt  Data2 gt       lt  Account1 gt       lt Account2 gt           lt Data1 gt data1 lt  Data1 gt           lt Data2 gt data2 lt  Data2 gt       lt  Account2 gt    lt  Username2 gt    As you can see the heirachy is    Username  string of dict     Account  each account in the List     Account data  ie class properties      Obtaining this layout from a Dictionary lt Username  List lt Account gt  gt  is the tricky bit  and the essence of this question   There are plenty of  how to  responses here on serialisation  which is my fault since I didn t make it clearer early on  but now I m looking for a definite solution

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It really depends on what you re storing  If you re talking about structured data  then either XML or a very lightweight SQL RDBMS like SQLite or SQL Server Compact Edition will work well for you  The SQL solution becomes especially compelling if the data moves beyond a trivial size   If you re storing large pieces of relatively unstructured data  binary objects like images  for example  then obviously neither a database nor XML solution are appropriate  but given your question I m guessing it s more of the former than the latter

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The first thing I d look at is a database  However  serialization is an option  If you go for binary serialization  then I would avoid BinaryFormatter - it has a tendency to get angry between versions if you change fields etc  Xml via XmlSerialzier would be fine  and can be side-by-side compatible  i e  with the same class definitions  with protobuf-net if you want to try contract-based binary serialization  giving you a flat file serializer without any effort

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If you go the binary serialization route  Consider the speed at which a particular member of the datum needs to be accessed   If it is only a small collection  loading the whole file will make sense  but if it will be large  you might also consider an index file     Tracking Account Properties fields that are located at a specific address within the file can help you speed up access time  especially if you optimize that index file based on key usage   possibly even when you write to disk

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Just finished coding data storage for my current project  Here is my 5 cents   I started with binary serialization  It was slow  about 30 sec for load of 100 000 objects  and it was creating a pretty big file on the disk as well  However  it took me a few lines of code to implement and I got my all storage needs covered   To get better performance I moved on custom serialization  Found FastSerialization framework by Tim Haynes on Code Project  Indeed it is a few times faster  got 12 sec for load  8 sec for save  100K records  and it takes less disk space  The framework is built on the technique outlined by GalacticJello in a previous post    Then I moved to SQLite and was able to get 2 sometimes 3 times faster performance     6 sec for load and 4 sec for save  100K records  It includes parsing ADO NET tables to application types  It also gave me much smaller file on the disk  This article explains how to get best performance out of ADO NET  http   sqlite phxsoftware com forums t 134 aspx  Generating INSERT statements is a very bad idea  You can guess how I came to know about that     Indeed  SQLite implementation took me quite a bit of time plus careful measurement of time taking by pretty much every line of the code

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It depends on the amount of data you are looking to store  In reality there s no difference between flat files and XML  XML would probably be preferable since it provides a structure to the document  In practice    The last option  and a lot of applications use now is the Windows Registry  I don t personally recommend it  Registry Bloat  Corruption  other potential issues   but it is an option

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Depending on the compelexity of your Account object  I would recomend either XML or Flat file   If there are just a couple of values to store for each account  you could store them on a properties file  like this   account 1 somekey Some value account 1 someotherkey Some other value account 1 somedate 2009-12-21 account 2 somekey Some value 2 account 2 someotherkey Some other value 2       and so forth  Reading from a properties file should be easy  as it maps directly to a string dictionary   As to where to store this file  the best choise would be to store into AppData folder  inside a subfolder for your program  This is a location where current users will always have access to write  and it s kept safe from other users by the OS itself

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I recommend XML reader writer class for files because it is easily serialized    Serialization in C      Serialization  known as pickling in   python  is an easy way to convert an   object to a binary representation that   can then be e g  written to disk or   sent over a wire       It s useful e g  for easy saving of settings to a file       You can serialize your own classes if   you mark them with  Serializable    attribute  This serializes all members   of a class  except those marked as    NonSerialized     The following is code to show you how to do this   using System  using System Collections Generic  using System Text  using System Drawing    namespace ConfigTest     Serializable          public class ConfigManager               private string windowTitle    Corp           private string printTitle    Inventory            public string WindowTitle                       get                               return windowTitle                            set                               windowTitle   value                                   public string PrintTitle                       get                               return printTitle                            set                               printTitle   value                                    You then  in maybe a ConfigForm  call your ConfigManager class and Serialize it   public ConfigForm         InitializeComponent        cm   new ConfigManager        ser   new XmlSerializer typeof ConfigManager        LoadConfig       private void LoadConfig              try               if  File Exists filepath                         FileStream fs   new FileStream filepath  FileMode Open               cm    ConfigManager ser Deserialize fs               fs Close                       else                       MessageBox Show  Could not find User Configuration File n nCreating new file       User Config Not Found                FileStream fs   new FileStream filepath  FileMode CreateNew               TextWriter tw   new StreamWriter fs               ser Serialize tw  cm               tw Close                fs Close                          setupControlsFromConfig              catch  Exception ex                MessageBox Show ex Message             After it has been serialized  you can then call the parameters of your config file using cm WindowTitle  etc

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If your collection gets too big  I have found that Xml serialization gets quite slow   Another option to serialize your dictionary would be  roll your own  using a BinaryReader and BinaryWriter     Here s some sample code just to get you started   You can make these generic extension methods to handle any type of Dictionary  and it works quite well  but is too verbose to post here   class Account       public string AccountName   get  set        public int AccountNumber   get  set         internal void Serialize BinaryWriter bw                   Add logic to serialize everything you need here            Keep in synch with Deserialize         bw Write AccountName           bw Write AccountNumber              internal void Deserialize BinaryReader br                   Add logic to deserialize everythin you need here              Keep in synch with Serialize         AccountName   br ReadString            AccountNumber   br ReadInt32              class Program       static void Serialize string OutputFile                   Write to disk          using  Stream stream   File Open OutputFile  FileMode Create                         BinaryWriter bw   new BinaryWriter stream                  Save number of entries             bw Write accounts Count                foreach  KeyValuePair lt string  List lt Account gt  gt  accountKvp in accounts                                   Save each key value pair                 bw Write accountKvp Key                   bw Write accountKvp Value Count                   foreach  Account account in accountKvp Value                                        account Serialize bw                                                        static void Deserialize string InputFile                accounts Clear                Read from disk         using  Stream stream   File Open InputFile  FileMode Open                         BinaryReader br   new BinaryReader stream               int entryCount   br ReadInt32                for  int entries   0  entries  lt  entryCount  entries                                     Read in the key-value pairs                 string key   br ReadString                    int accountCount   br ReadInt32                    List lt Account gt  accountList   new List lt Account gt                     for  int i   0  i  lt  accountCount  i                                          Account account   new Account                        account Deserialize br                       accountList Add account                                     accounts Add key  accountList                                      static Dictionary lt string  List lt Account gt  gt  accounts   new Dictionary lt string  List lt Account gt  gt          static void Main string   args                string accountName    Bob           List lt Account gt  newAccounts   new List lt Account gt             newAccounts Add AddAccount  A   1            newAccounts Add AddAccount  B   2            newAccounts Add AddAccount  C   3            accounts Add accountName  newAccounts            accountName    Tom           newAccounts   new List lt Account gt             newAccounts Add AddAccount  A1   11            newAccounts Add AddAccount  B1   22            newAccounts Add AddAccount  C1   33            accounts Add accountName  newAccounts            string saveFile     C  accounts bin            Serialize saveFile               clear it out to prove it works         accounts Clear             Deserialize saveFile              static Account AddAccount string AccountName  int AccountNumber                Account account   new Account            account AccountName   AccountName          account AccountNumber   AccountNumber          return account

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All of the above are good answers  and generally solve the problem   If you need an easy  free way to scale to millions of pieces of data  try out the ESENT Managed Interface project on GitHub or from NuGet      ESENT is an embeddable database storage engine  ISAM  which is part of Windows  It provides reliable  transacted  concurrent  high-performance data storage with row-level locking  write-ahead logging and snapshot isolation  This is a managed wrapper for the ESENT Win32 API    It has a PersistentDictionary object that is quite easy to use   Think of it as a Dictionary   object  but it is automatically loaded from and saved to disk without extra code   For example        lt summary gt      Ask the user for their first name and see if we remember      their last name       lt  summary gt  public static void Main         PersistentDictionary lt string  string gt  dictionary   new PersistentDictionary lt string  string gt   Names        Console WriteLine  What is your first name         string firstName   Console ReadLine        if  dictionary ContainsKey firstName                 Console WriteLine  Welcome back  0   1    firstName  dictionary firstName              else               Console WriteLine  I don t know you   0   What is your last name    firstName           dictionary firstName    Console ReadLine            To answer George s question      Supported Key Types      Only these types are supported as   dictionary keys       Boolean   Byte    Int16 UInt16    Int32   UInt32   Int64 UInt64  Float   Double    Guid    DateTime TimeSpan   String        Supported Value Types      Dictionary values can be any of the   key types  Nullable versions of the   key types  Uri  IPAddress or a   serializable structure  A structure is   only considered serializable if it   meets all these criteria           The structure is marked as   serializable        Every member of the   struct is either    1     A primitive data type  e g  Int32    2     A String  Uri or IPAddress   3     A serializable structure       Or  to put it another way  a   serializable structure cannot contain   any references to a class object  This   is done to preserve API consistency    Adding an object to a   PersistentDictionary creates a copy of   the object though serialization    Modifying the original object will not   modify the copy  which would lead to   confusing behavior  To avoid those   problems the PersistentDictionary will   only accept value types as values       Can Be Serialized   Serializable  struct Good         public DateTime  Received        public string Name        public Decimal Price        public Uri Url          Can   t Be Serialized  Serializable  struct Bad         public byte   Data     arrays aren   t supported       public Exception Error     reference object

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In my experience in most cases JSON in a file is enough  mostly you need to store an array or an object or just a single number or string   I rarely need SQLite  which needs more time for setting it up and using it  most of the times it s overkill

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A fourth option to those you mention are binary files  Although that sounds arcane and difficult  it s really easy with the serialization API in  NET   Whether you choose binary or XML files  you can use the same serialization API  although you would use different serializers   To binary serialize a class  it must be marked with the  Serializable  attribute or implement ISerializable   You can do something similar with XML  although there the interface is called IXmlSerializable  and the attributes are  XmlRoot  and other attributes in the System Xml Serialization namespace   If you want to use a relational database  SQL Server Compact Edition is free and very lightweight and based on a single file

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A lot of the answers in this thread attempt to overengineer the solution  If I m correct  you just want to store user settings   Use an  ini file or App Config file for this   If I m wrong  and you are storing data that is more than just settings  use a flat text file in csv format  These are fast and easy without the overhead of XML  Folks like to poo poo these since they aren t as elegant  don t scale nicely and don t look as good on a resume  but it might be the best solution for you depending on what you need

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XML is easy to use  via serialization   Use Isolated storage    See also How to decide where to store per-user state  Registry  AppData  Isolated Storage   public class UserDB           actual data to be preserved for each user     public int A       public string Z           metadata             public DateTime LastSaved      public int eon       private string dbpath        public static UserDB Load string path                UserDB udb          try                       System Xml Serialization XmlSerializer s new System Xml Serialization XmlSerializer typeof UserDB                using System IO StreamReader reader  System IO File OpenText path                                 udb   UserDB  s Deserialize reader                                   catch                       udb  new UserDB                      udb dbpath  path            return udb              public void Save                 LastSaved  System DateTime Now          eon            var s  new System Xml Serialization XmlSerializer typeof UserDB            var ns  new System Xml Serialization XmlSerializerNamespaces            ns Add                   System IO StreamWriter writer  System IO File CreateText dbpath           s Serialize writer  this  ns           writer Close

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I have done several  stand alone  apps that have a local data store   I think the best thing to use would be SQL Server Compact Edition  formerly known as SQLAnywhere    It s lightweight and free   Additionally  you can stick to writing a data access layer that is reusable in other projects plus if the app ever needs to scale to something bigger like full blown SQL server  you only need to change the connection string

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I d store the file as JSON  Since you re storing a dictionary which is just a name value pair list then this is pretty much what json was designed for  There a quite a few decent  free  NET json libraries - here s one but you can find a full list on the first link

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My first inclination is an access database   The  mdb files are stored locally  and can be encrypted if that is deemed necessary   Though XML or JSON would also work for many scenarios   Flat files I would only use for read only  non-search  forward read only  information   I tend to prefer csv format to set width

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Without knowing what your data looks like  i e  the complexity  size  etc   XML is easy to maintain and easily accessible   I would NOT use an Access database  and flat files are more difficult to maintain over the long haul  particularly if you are dealing with more than one data field element in your file   I deal with large flat-file data feeds in good quantities daily  and even though an extreme example  flat-file data is much more difficult to maintain than the XML data feeds I process   A simple example of loading XML data into a dataset using C    DataSet reportData   new DataSet     reportData ReadXml fi FullName     You can also check out LINQ to XML as an option for querying the XML data     HTH

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Keep it simple - as you said  a flat file is sufficient  Use a flat file   This is assuming that you have analyzed your requirements correctly  I would skip the serializing as XML step  overkill for a simple dictionary  Same thing for a database

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If your data is complex  high in quantity or you need to query it locally then object databases might be a valid option  I d suggest looking at Db4o or Karvonite

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