Whereas one approach is to implement the ICloneable
interface (described here, so I won't regurgitate), here's a nice deep clone object copier I found on The Code Project a while ago and incorporated it into our code.
As mentioned elsewhere, it requires your objects to be serializable.
using System;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
/// <summary>
/// Reference Article http://www.codeproject.com/KB/tips/SerializedObjectCloner.aspx
/// Provides a method for performing a deep copy of an object.
/// Binary Serialization is used to perform the copy.
/// </summary>
public static class ObjectCopier
{
/// <summary>
/// Perform a deep copy of the object via serialization.
/// </summary>
/// <typeparam name="T">The type of object being copied.</typeparam>
/// <param name="source">The object instance to copy.</param>
/// <returns>A deep copy of the object.</returns>
public static T Clone<T>(T source)
{
if (!typeof(T).IsSerializable)
{
throw new ArgumentException("The type must be serializable.", nameof(source));
}
// Don't serialize a null object, simply return the default for that object
if (ReferenceEquals(source, null)) return default;
using var Stream stream = new MemoryStream();
IFormatter formatter = new BinaryFormatter();
formatter.Serialize(stream, source);
stream.Seek(0, SeekOrigin.Begin);
return (T)formatter.Deserialize(stream);
}
}
The idea is that it serializes your object and then deserializes it into a fresh object. The benefit is that you don't have to concern yourself about cloning everything when an object gets too complex.
In case of you prefer to use the new extension methods of C# 3.0, change the method to have the following signature:
public static T Clone<T>(this T source)
{
// ...
}
Now the method call simply becomes objectBeingCloned.Clone();
.
EDIT (January 10 2015) Thought I'd revisit this, to mention I recently started using (Newtonsoft) Json to do this, it should be lighter, and avoids the overhead of [Serializable] tags. (NB @atconway has pointed out in the comments that private members are not cloned using the JSON method)
/// <summary>
/// Perform a deep Copy of the object, using Json as a serialization method. NOTE: Private members are not cloned using this method.
/// </summary>
/// <typeparam name="T">The type of object being copied.</typeparam>
/// <param name="source">The object instance to copy.</param>
/// <returns>The copied object.</returns>
public static T CloneJson<T>(this T source)
{
// Don't serialize a null object, simply return the default for that object
if (ReferenceEquals(source, null)) return default;
// initialize inner objects individually
// for example in default constructor some list property initialized with some values,
// but in 'source' these items are cleaned -
// without ObjectCreationHandling.Replace default constructor values will be added to result
var deserializeSettings = new JsonSerializerSettings {ObjectCreationHandling = ObjectCreationHandling.Replace};
return JsonConvert.DeserializeObject<T>(JsonConvert.SerializeObject(source), deserializeSettings);
}
What if I want to obtain a distinct list based on one or more properties?
Simple! You want to group them and pick a winner out of the group.
List<Person> distinctPeople = allPeople
.GroupBy(p => p.PersonId)
.Select(g => g.First())
.ToList();
If you want to define groups on multiple properties, here's how:
List<Person> distinctPeople = allPeople
.GroupBy(p => new {p.PersonId, p.FavoriteColor} )
.Select(g => g.First())
.ToList();
Note: Certain query providers are unable to resolve that each group must have at least one element, and that First is the appropriate method to call in that situation. If you find yourself working with such a query provider, FirstOrDefault may help get your query through the query provider.
Note2: Consider this answer for an EF Core (prior to EF Core 6) compatible approach. https://stackoverflow.com/a/66529949/8155
Best Answer
I ended up using a C# program in conjunction with the SharePoint web services to accomplish this. I also used the extension methods (GetXElement, GetXmlNode) on Eric White's blog here to convert between XMLNodes and XElements which made the XML from SharePoint easier to work with.
Below is a template for most of the code needed to transfer list data, including attachments, from one SharePoint List (either 2003 or 2007) to another one:
1) This is the code moves attachments after a new item has been added to the target list.
2) Code that iterates through the old SharePoint List and populates the new one.
3) Miscellaneous support code for this sample.