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Question

Help required in adding new methods, properties into existing classes dynamically

Answer 1

+1 A:

If you allow them to inherit new Address and Employee classes from your base classes that should do the trick.

public class Employee
{
  public string FirstName { get; set; }
  public string LastName { get; set; }
  public string AddressCollection { get; set; }
}

public class EmployeeCollection<T> : List<T> where T : Employee
{
  public bool Add(T Data)
  {
    return this.Add(Data);
  }
}

Then a derived employee would look something like this

public class EmployeePlus : Employee
{
  public string PassportNo { get; set; }
}

If you want the stronly typed collection to be of EmployeePlus you can simple define your collections like this, if you need to...

public class EmployeeCollection<T> : List<T> where T : Employee
{
  public bool Add(T Data)
  {
    return this.Add(Data);
  }
}

Now a strongly typed collection of Employee and derived objects can be used as follows

EmployeeCollection<EmployeePlus> employees = 
  new EmployeeCollection<EmployeePlus>();

Chris Taylor 2010-05-30 07:16:46

You were right - of course - partial classes only work when you have access to the source code :-( I could have sworn I had used that with stuff provided in a DLL before - but I must have been dreaming that.... :-)

marc_s 2010-05-30 08:33:39

Chris, in this case i believe we need to rebind the controls with the new type. Reason why i ask is that because for example, there is a data grid which is bound to employee class collection. Now that it is getting modified to use EmployeePLus class, In view (UI) we need to rebind all the controls which is using Employee class as its data object.

Bepenfriends 2010-06-03 02:20:59

Answer 2

A:

This seems quite an odd setup, but there's a number of ways you could do what you want:

Class inheritance (probably making your base classes abstract but partial classes are another option)
working to interfaces instead of classes and letting your customers worry about the implementation
extension methods (ref1, ref2) which are commonly used to extend third party code, but are not normally expected to be used.
decorators

Normally speaking I'd expect to be working with Interfaces in your kind of scenario, but if you're also trying to mix in behaviour I'd hazard a guess that refactoring that may be too painful at this point and class inheritance is where you'll end up.

annakata 2010-05-30 07:38:45

Answer 3

A:

Try to work with MSIL

public class RunTimeObject<T> where T : class
{

    void EmitGetter(MethodBuilder methodBuilder, FieldBuilder fieldBuilder)
    {
        ILGenerator ilGenerator = methodBuilder.GetILGenerator();
        ilGenerator.Emit(OpCodes.Ldarg_0);
        ilGenerator.Emit(OpCodes.Ldfld, fieldBuilder);
        ilGenerator.Emit(OpCodes.Ret);
    }

    void EmitSetter(MethodBuilder methodBuilder, FieldBuilder fieldBuilder)
    {
        ILGenerator ilGenerator = methodBuilder.GetILGenerator();
        ilGenerator.Emit(OpCodes.Ldarg_0);
        ilGenerator.Emit(OpCodes.Ldarg_1);
        ilGenerator.Emit(OpCodes.Stfld, fieldBuilder);
        ilGenerator.Emit(OpCodes.Ret);
    }

    public object CreateNewObject(T obj)
    {

        AssemblyName assemblyName = new AssemblyName { Name = "assembly" };
        AssemblyBuilder assemblyBuilder = Thread.GetDomain().DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);
        ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule("module");
        TypeBuilder typeBuilder = moduleBuilder.DefineType("DynamicType", TypeAttributes.Public | TypeAttributes.Class);

        foreach (var prop in obj.GetType().GetProperties())
        {
            FieldBuilder field = typeBuilder.DefineField("_" + prop.Name, typeof(string), FieldAttributes.Private);

            PropertyBuilder propertyBuilder =
                typeBuilder.DefineProperty(prop.Name,
                                 PropertyAttributes.None,
                                 typeof(string),
                                 new Type[] { typeof(string) });

            MethodAttributes methodAttributes =
                MethodAttributes.Public |
                MethodAttributes.HideBySig;

            MethodBuilder methodBuilderGetter =
                typeBuilder.DefineMethod("get_value",
                                           methodAttributes,
                                           typeof(string),
                                           Type.EmptyTypes);

            EmitGetter(methodBuilderGetter, field);


            MethodBuilder methodBuilderSetter =
                typeBuilder.DefineMethod("set_value",
                                           methodAttributes,
                                           null,
                                           new Type[] { typeof(string) });

            EmitSetter(methodBuilderSetter, field);


            propertyBuilder.SetGetMethod(methodBuilderGetter);
            propertyBuilder.SetSetMethod(methodBuilderSetter);
        }

        Type dynamicType = typeBuilder.CreateType();

        var dynamicObject = Activator.CreateInstance(dynamicType);

        var properties = dynamicType.GetProperties();

        int count = 0;

        foreach (var item in obj.GetType().GetProperties())
            properties[count++].SetValue(dynamicObject, item.GetValue(obj, null), null);

        return dynamicObject;

    }
}

Daniel Bern 2010-05-30 15:06:07

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Help required in adding new methods, properties into existing classes dynamically

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