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C#, LinqToSql and Entity Classes and SqlMetal.exe



What is DataContext:
            Bridge that allows execution of Linq query expression on actual database. Pass you Linq expressions to DataContext to execute.

Simple LinqToSql Entity:
[Table]
public class Inventory
{
            [Column]
            public string Make;
            [Column]
            public string Color;
            [Column]
            public string PetName;
            // Identify the primary key.
            [Column(IsPrimaryKey = true)]
            public int CarID;

            public override string ToString()
                        {
                                    return string.Format("ID = {0}; Make = {1}; Color = {2};                                                                                                                                                        PetName = {3}",
                                    CarID, Make.Trim(), Color.Trim(), PetName.Trim());
                        }
}

Getting Data From database:

            DataContext db = new DataContext(connectionString);
            // Now create a Table<> type.
            Table<Inventory> invTable = db.GetTable<Inventory>();

DataConext should be Strongly Typed:

            class AutoLotDatabase : DataContext
                        {
                                    public Table<Inventory> Inventory;
                                    public AutoLotDatabase(string connectionString)
                                                                                                : base(connectionString){}
                        }
var bimmers = from s in db.Inventory where s.Make == "BMW" select s;

Specifying Associations in Entity Classes:

[Table(Name="Customers")]
public partial class Customers :
            INotifyPropertyChanging, INotifyPropertyChanged
            {
                        private EntitySet<Orders> _Orders;
                        [Association(Name="FK_Orders_Customers", Storage="_Orders",
                                                            OtherKey="CustID", DeleteRule="NO ACTION")]
                        public EntitySet<Orders> Orders
                        { get; set; }

            }



To generate the Entities directly from your database.

sqlmetal.exe  /server(Specifies the server hosting the database)
                          /database(Specifies the name of the database to read metadata from)
                          /user(Specifies user ID to log in to the server)
                          /password(Specifies password to log in to the server)
                          /views(Generate code based on existing database views)
                          /functions(Extract database functions)
                          /sprocs(Extract stored procedures sqlmetal.exe Command-Line
                          /code(Output results as C# code or VB, if you set the /language flag)
                          /language(Language used to defined the generated types)
                          /namespace(Specifies the namespace to define the generated types)
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