Copy Linq objects

[=?Utf-8?B?Tmljaw==?=]

Hello,

I'm using LINQ to access a SQL Server database. The user needs to be able to
duplicate a record. Is there an easy way to do this? I rather not have to set
each property from one to the other. I need to copy all the relationships
too.

Thanks for any help, I really appreciate it.

Thanks,
Nick

[Marc Gravell]

I don't think there is anything built in; however, you can probably
automate much of the work - the following makes a fairly crude (but very
quick) shallow-copy using the default .ctor() [making a point of
ignoring the primary key field(s) - although it isn't really
LINQ-specific] - with the advantage that since this is an extension
method, you could replace on an individual basis by adding a specific
Clone() method to the partial class, and it will be
chosen by the compiler.

using System;
using System.Data.Lin q.Mapping;
using System.Linq;
using System.Linq.Exp ressions;
static class Program
{
static void Main()
{
Foo foo = new Foo { Id = 16, Name = "Fred", DoB = DateTime.Today };
Foo bar = foo.Clone();
}
}
class Foo
{
[Column(IsPrimar yKey = true)] // PK
public int Id { get; set; }
[Column] // test with non-PK ColumnAttribute
public string Name { get; set; }
// test w/o ColumnAttribute
public DateTime DoB { get; set; }
}
public static class ObjectExt
{
public static T Clone<T>(this T obj) where T : new()
{
return ObjectExtCache< T>.Clone(obj);
}
static class ObjectExtCache< Twhere T : new()
{
private static readonly Func<T, Tcloner;
static ObjectExtCache( )
{
ParameterExpres sion param = Expression.Para meter(typeof(T) ,
"in");

var bindings = from prop in typeof(T).GetPr operties()
where prop.CanRead && prop.CanWrite
let column = Attribute.GetCu stomAttribute(p rop,
typeof(ColumnAt tribute))
as ColumnAttribute
where column == null || !column.IsPrima ryKey
select (MemberBinding) Expression.Bind (prop,
Expression.Prop erty(param, prop));

cloner = Expression.Lamb da<Func<T,T>>(
Expression.Memb erInit(
Expression.New( typeof(T)), bindings), param).Compile( );
}
public static T Clone(T obj)
{
return cloner(obj);
}

}
}

[=?Utf-8?B?Tmljaw==?=]

Marc,

I'm really late with my reply, but I very much appreciate your help. Your
code was very helpful.

Thanks,
Nick

"Marc Gravell" wrote:

I don't think there is anything built in; however, you can probably
automate much of the work - the following makes a fairly crude (but very
quick) shallow-copy using the default .ctor() [making a point of
ignoring the primary key field(s) - although it isn't really
LINQ-specific] - with the advantage that since this is an extension
method, you could replace on an individual basis by adding a specific
Clone() method to the partial class, and it will be
chosen by the compiler.

using System;
using System.Data.Lin q.Mapping;
using System.Linq;
using System.Linq.Exp ressions;
static class Program
{
static void Main()
{
Foo foo = new Foo { Id = 16, Name = "Fred", DoB = DateTime.Today };
Foo bar = foo.Clone();
}
}
class Foo
{
[Column(IsPrimar yKey = true)] // PK
public int Id { get; set; }
[Column] // test with non-PK ColumnAttribute
public string Name { get; set; }
// test w/o ColumnAttribute
public DateTime DoB { get; set; }
}
public static class ObjectExt
{
public static T Clone<T>(this T obj) where T : new()
{
return ObjectExtCache< T>.Clone(obj);
}
static class ObjectExtCache< Twhere T : new()
{
private static readonly Func<T, Tcloner;
static ObjectExtCache( )
{
ParameterExpres sion param = Expression.Para meter(typeof(T) ,
"in");

var bindings = from prop in typeof(T).GetPr operties()
where prop.CanRead && prop.CanWrite
let column = Attribute.GetCu stomAttribute(p rop,
typeof(ColumnAt tribute))
as ColumnAttribute
where column == null || !column.IsPrima ryKey
select (MemberBinding) Expression.Bind (prop,
Expression.Prop erty(param, prop));

cloner = Expression.Lamb da<Func<T,T>>(
Expression.Memb erInit(
Expression.New( typeof(T)), bindings), param).Compile( );
}
public static T Clone(T obj)
{
return cloner(obj);
}

}
}

[Marc Gravell]

No problem,

Marc

[=?Utf-8?B?UGFua2Fq?=]

Please go to http://www.a2zdotnet.com/Default.aspx
for step by step tutorials for beginers in LINQ sections.

--
regards,
Pankaj
http://www.A2ZDotNet.com
"Nick" wrote:

Hello,

I'm using LINQ to access a SQL Server database. The user needs to be able to
duplicate a record. Is there an easy way to do this? I rather not have to set
each property from one to the other. I need to copy all the relationships
too.

Thanks for any help, I really appreciate it.

Thanks,
Nick