If you are interested in what LINQ to SQL generates and don't have Orcas installed or available right now but use
CodeSmith try the following template to generate very similar code.

The primary difference is that this writes out the System types rather than the C# aliases
(e.g. System.Int32 instead of int) but that could easily be changed but is binary compatible
and otherwise almost identical to the source.

Download LINQ to SQL template (CodeSmith) (4 KB)

<%@ CodeTemplate Src="LinqFunctions.cs" Inherits="LinqFunctions" Language="C#" TargetLanguage="C#"
  Description="Generates a data context and entities for given tables." %>
<%@ Assembly Name="SchemaExplorer" %>
<%@ Assembly Name="System.Data" %>
<%@ Import Namespace="SchemaExplorer" %>
<%@ Import Namespace="System.Collections.Generic" %>
<%@ Import Namespace="System.Data" %>
<%@ Property Name="DataContextClassName" Type="System.String" Category="Naming" Optional="True"Description="Name of the data context class to generate." %>
<%@ Property Name="Namespace" Type="System.String" Category="Naming" Optional="True" Description="Namespace for the data context class to generate." %>
<%@ Property Name="SourceTables" Type="SchemaExplorer.TableSchemaCollection" Category="Connection"Description="Tables to be mapped." %>
<%SchemaExplorer.DatabaseSchema database = SourceTables[0].Database;
string className = (String.IsNullOrEmpty(DataContextClassName)) ? DatabaseName(database) + "DataContext" : DataContextClassName;
Dictionary<TableSchema, List<TableKeySchema>> reverseForeignKeys = new Dictionary<TableSchema, List<TableKeySchema>>();
foreach(TableSchema table in SourceTables) {
    foreach(TableKeySchema keySchema in table.ForeignKeys) {
        if (reverseForeignKeys.ContainsKey(keySchema.PrimaryKeyTable)) {
            reverseForeignKeys[keySchema.PrimaryKeyTable].Add(keySchema);
        }
        else {
            List<TableKeySchema> keySchemas = new List<TableKeySchema>();
            keySchemas.Add(keySchema);
            reverseForeignKeys.Add(keySchema.PrimaryKeyTable, keySchemas);
        }
    }
}%>//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//     CodeSmith template DeLINQuent.cst v0.1
//     Generated by <%=CurrentUserName()%> at <%=DateTime.Now%>
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------
namespace <%=Namespace%>{
    public partial class <%=className%> : global::System.Data.Linq.DataContext
    {
        [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
        public <%=className%>(string connection) :
                base(connection)
        {
        }

        [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
        public ProjectDataContext(global::System.Data.IDbConnection connection) :
                base(connection) {
        }
<%    foreach(TableSchema table in SourceTables) {
        string entityName = EntityName(table);
        string propertyName = TableName(table);%>
        public global::System.Data.Linq.Table<<%=entityName%>> <%=propertyName%> {
            get {
                return this.GetTable<<%=entityName%>>();
            }
        }
<%     } %>
    }<%    foreach(TableSchema table in SourceTables) {
        string entityName = EntityName(table);%>
    [global::System.Data.Linq.Table(Name="<%=table.FullName%>")]
    public partial class <%=entityName%> :global::System.Data.Linq.INotifyPropertyChanging,global::System.ComponentModel.INotifyPropertyChanged
    {
<%    foreach(ColumnSchema column in table.Columns) {%>
        private <%=NullableSystemType(column)%> _<%=PropertyName(column)%>;
<%    }
      if (table.ForeignKeys.Count > 0) {%>
<%        foreach(TableKeySchema keySchema in table.ForeignKeys) {
            string foreignEntityName = EntityName(keySchema.PrimaryKeyTable);%>
        private global::System.Data.Linq.EntitySet<<%=foreignEntityName%>> _<%=foreignEntityName%>;<%
          }
      }
      if (reverseForeignKeys.ContainsKey(table)) {%>
<%        foreach(TableKeySchema keySchema in reverseForeignKeys[table]) {            string propertyName = TableName(keySchema.ForeignKeyTable);%>
        private global::System.Data.Linq.EntityRet<<%=EntityName(keySchema.ForeignKeyTable)%>> _<%=propertyName%>;
<%        }
      } %>
        [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
        public <%=entityName%>() {
        }
<%    foreach(ColumnSchema column in table.Columns) {
        string propertyName = PropertyName(column);%>
        [global::System.Data.Linq.Column(Storage="_<%=propertyName%>", Name="<%=column.Name%>", DBType="<%=AttributeColumnDbType(column)%>"<%
            if (column.IsPrimaryKeyMember) { %>, IsPrimaryKey=true<% }
            if (!column.AllowDBNull) { %>, CanBeNull=false<% } %>)]
        public <%=NullableSystemType(column)%> <%=propertyName%> {
            get {
                return this._<%=propertyName%>;
            }
            set {
                if (this._<%=propertyName%> != value) {
                    this.OnPropertyChanging("<%=propertyName%>");
                    this._<%=propertyName%> = value;
                    this.OnPropertyChanged("<%=propertyName%>");
                }
            }
        }

<%    } %>
<%    foreach(TableKeySchema keySchema in table.ForeignKeys) {
        string propertyName = EntityName(keySchema.PrimaryKeyTable);
        string tableName = TableName(keySchema.PrimaryKeyTable);%>
        [global::System.Data.Linq.Association(Name="<%=keySchema.Name%>",
            Storage="_<%=propertyName%>", OtherKey="<%=AttributeColumnList(keySchema.ForeignKeyMemberColumns)%>",
            ThisKey="<%=AttributeColumnList(keySchema.PrimaryKeyMemberColumns)%>", IsForeignKey=true)]
        public <%=propertyName%> <%=propertyName%> {
            get {
                return this._<%=propertyName%>.Entity;
            }
            set {
                if (this._<%=propertyName%>.Entity != value) {
                    this.OnPropertyChanging("<%=propertyName%>");
                    if ((this._<%=propertyName%>.Entity != null)) {
                        <%=propertyName%> temp = this._<%=propertyName%>.Entity;
                        this._<%=propertyName%>.Entity = null;
                        temp.<%=TableName(table)%>.Remove(this);
                    }
                    this._<%=propertyName%>.Entity = value;
                    if ((value != null)) {
                        value.<%=TableName(table)%>.Add(this);
                    }
                    this.OnPropertyChanged("<%=propertyName%>");
                }
            }
        }
<%    } %>
<%    if (reverseForeignKeys.ContainsKey(table)) {
        foreach(TableKeySchema keySchema in reverseForeignKeys[table]) {
            string propertyName = TableName(keySchema.ForeignKeyTable);%>
        [global::System.Data.Linq.Association(Name="<%=keySchema.Name%>",
            Storage="_<%=propertyName%>", OtherKey="<%=AttributeColumnList(keySchema.PrimaryKeyMemberColumns)%>",
            ThisKey="<%=AttributeColumnList(keySchema.ForeignKeyMemberColumns)%>")]
        public IEnumerable<<%=EntityName(keySchema.ForeignKeyTable)%>> <%=propertyName%> {
            get {
                return this._<%=propertyName%>;
            }
        }

<%             }
        } %>
        public event global::System.ComponentModel.PropertyChangedEventHandler PropertyChanging;
        public event global::System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

        [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
        protected void OnPropertyChanging(string propertyName) {
            if (this.PropertyChanging != null)
                this.PropertyChanging(this, new global::System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }

[global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
        protected void OnPropertyChanged(string propertyName) {
            if (this.PropertyChanged != null)
                this.PropertyChanged(this, new global::System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }
    }
<%     } %>
}

[)amien

I've been busy working on some LINQ to SQL (formerly DLINQ) apps that have been going well bar a NullReferenceException thrown at me from deep in the bowels of LINQ and it's change tracker. A cursory glance in debug showed none of the properties that represent columns were null...

The null was actually a collection property that represented a one-to-many relationship that was automatically created using the foreign key constraints in the database. Normally this is set to an empty EntitySet however I was failing to call the default constructor from my new useful constructor.

The moral of the story is always call the default constructor with this(), especially when extending generated code. So much for persistence ignorance.

public partial class Invoice
{
    public Invoice(int number) : this() {
        this.number = number;
    }
}

[)amien

I'm a big fan of the Web Application type that was previously available as an add-on to Visual Studio 2005 but thankfully got promoted to a standard citizen with Service Pack 1.

So with a little more time on my hands lately I've been delving into the wonder that is LINQ - part of the forthcoming Orcas release of technologies.

For those who've been living under a rock LINQ is a set of extensions to .NET that let you perform queries on objects in much the same way you would do on a database with SQL (except the syntax is backwards by comparison).

Now while the LINQ Preview CTP installs LINQ projects for C# Class Libraries, Windows Applications and Console Applications it inconveniently misses-out Web Applications!

You can drop this ZIP file in your %UserProfile%\My Documents\Visual Studio 2005\Templates\ProjectTemplates\Visual C# to gain a new ASP.NET LINQ Web Application project type for you to start with as often as you like as shown:

Or if you want to modify an existing Web Application simply:

1. Open up the .csproj file in Notepad and replace
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   with
   <Import Project="$(ProgramFiles)\LINQ Preview\Misc\Linq.targets" />
2. Add project references to:
   System.Data.DLinq
   System.Query
   System.Xml.XLinq

Hopefully more LINQ related posts as I get to grips with it.

[)amien