What is the best way to combine two objects at runtime using C #?

Question

I have two objects, and I want to combine them:

public class Foo { public string Name { get; set; } } public class Bar { public Guid Id { get; set; } public string Property1 { get; set; } public string Property2 { get; set; } public string Property3 { get; set; } public string Property4 { get; set; } } 

To create:

 public class FooBar { public string Name { get; set; } public Guid Id { get; set; } public string Property1 { get; set; } public string Property2 { get; set; } public string Property3 { get; set; } public string Property4 { get; set; } } 

I will know the structure of Foo at runtime. A bar can be of any type at runtime. I would like to have a method that will be given a type, and it combines this type with Foo. For example, in the above script, the method was set to Bar at run time, and I combined it with Foo.

What would be the best way to do this? Can this be done using LINQ Expressions or do I need to generate it dynamically or is there another way? I'm still exploring the new LINQ namespace in C # 3.0, so sorry ignorance if this cannot be done with LINQ Expressions. This is also the first time I've ever had to do something like this with C #, so I'm not completely sure of all the options available to me.

Thanks for any options provided.

EDIT

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This is strictly for adding meta information to the type provided to me for serialization. This scenario prevents user objects from knowing the meta-information that must be added before it is serialized. I asked two options before asking this question, and I just wanted to know if there were any more before deciding which one to use.

Here are two options I came up with:

Manipulating a serialized string of the type given to me after it was serialized by adding meta-information.

Wrapping the type given to me, which is similar to what @Zxpro mentioned, but mine was slightly different, which is good. This will simply force the user of my API to follow the standard, which is not so bad as everyone is concerned with the configuration configuration:

 public class Foo<T> { public string Name { get; set; } public T Content { get; set; } } 

EDIT

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Thanks to everyone for their answers. I decided to wrap the object as described above, and I answered @Zxpro since most liked this approach.

If anyone else comes across this question, feel free to post messages if you think there might be a better way.

Answer 1

If you don't mind grouping, not grouping:

 public class FooEx<T> { public Foo Foo { get; set; } public T Ex { get; set; } } 

Answer 2

UNTESTED, but using the Reflection.Emit API, something like this should work:

 public Type MergeTypes(params Type[] types) { AppDomain domain = AppDomain.CurrentDomain; AssemblyBuilder builder = domain.DefineDynamicAssembly(new AssemblyName("CombinedAssembly"), AssemblyBuilderAccess.RunAndSave); ModuleBuilder moduleBuilder = builder.DefineDynamicModule("DynamicModule"); TypeBuilder typeBuilder = moduleBuilder.DefineType("CombinedType"); foreach (var type in types) { var props = GetProperties(type); foreach (var prop in props) { typeBuilder.DefineField(prop.Key, prop.Value, FieldAttributes.Public); } } return typeBuilder.CreateType(); } private Dictionary<string, Type> GetProperties(Type type) { return type.GetProperties().ToDictionary(p => p.Name, p => p.PropertyType); } 

APPLICATION:

 Type combinedType = MergeTypes(typeof(Foo), typeof(Bar)); 

Answer 3

Unfortunately, this is not something you can do easily. The best you can do is create an anonymous type as part of the LINQ query, but it will only have a local scope, and this will only be useful to you in the method in which you create it.

When .NET 4 comes out, there is a new dynamic runtime library that can help you.

Answer 4

Besides the “Why” question, the only way I can think of is to take two objects, one known and one unknown, and combine them into a new type, using Reflection.Emit to generate a new type at runtime.

There are examples on MSDN. You will need to determine the weather you would like to combine fields with the same name or have a known type that replaces an unknown type.

As far as I can tell, there is no way to do this in LINQ.

Since all you are interested in is “Properties,” it should be fairly simple to use this article as an example. Leave the IL to create methods, and you're good to go.

Answer 5

As others have pointed out, there is no way to "merge" them (if you are thinking about select * with multiple tables in SQL, for example). Your closest counterpart will take the route that Zxpro provided and "group" them into a common class.

What, in fact, would you like to accomplish with "merging" them? Declaring properties will obviously have the greatest effect of convenience when writing code and security at compile time, but if you cannot specify a type, then there is no way to do this. If you are just looking for a generic "property bag" container, then an existing data structure such as Dictionary<T,T> or Hashtable should be able to handle this.

Answer 6

If you can add a method to the metadata class, you can do something like the following

 public class Foo { public string Name { get; set; } public void SerializeWithMetadata(Bar bar) { var obj = new { Name = this.Name, Guid = bar.Guid, Property1 = Bar.Property1 } //Serialization code goes here } } public class Bar { public Guid Id { get; set; } public string Property1 { get; set; } public string Property2 { get; set; } public string Property3 { get; set; } public string Property4 { get; set; } } 

I am not sure I recommend this exact approach. I basically left it here to display anonymous types as an option worth exploring

Answer 7

Another variant:

Change the first class as follows

 public class Foo { public string Name { get; set; } [System.Xml.Serialization.XmlAnyElementAttribute()] public XmlElement Any {get;set;} } 

Take the second class and serialize it into an XmlElement, for example:

 XmlElement SerializeToElement(Type t, object obj) { XmlSerializer ser = new XmlSerializer(t); StringWriter sw = new StringWriter(); using (XmlWriter writer = XmlWriter.Create(sw, settings)) ser.Serialize(writer, obj); string val = sw.ToString(); XmlDocument doc = new XmlDocument(); doc.LoadXml(xmlString); return (XmlElement)doc.DocumentElement; } 

Set the Any property to XmlElement and serialize it. You will see XML for another class embedded in the document, complete with all namespaces

You can even avoid this if the class was generated using Xsd.exe, if you use the following as an element:

 <xs:any namespace="##any" processContents="lax" /> 

I believe you can also get away with an XmlElements array for more than one subclass.

Deserializaing should be subject to XmlElements validation, and then looking for a suitable class, or perhaps using a namespace to search for a class.

This is much more accurate than messing with string manipulations.