Visual Basic

class ChildClass
{ }

class MyClass
{
    public ICollection<ChildClass> Children { get; set; }

    public MyClass()
    {
        Children = new HashSet<ChildClass>() { new ChildClass() };
    }
}

T CopyEntity<T>(T entity)
    where T : class, new()
{
    T copy = new T();
    // actual copying omitted here
    // for testing only the return type matters
    return copy;
}

void Test()
{
    MyClass myClass = new MyClass();
    dynamic children = typeof(MyClass).GetProperty("Children").GetValue(myClass);
    dynamic child = Enumerable.ElementAt(children, 0);
    dynamic copy = CopyEntity(child);
    // copy is of type ChildClass
}

Class ChildClass
End Class

Class [MyClass]
    Public Property Children() As ICollection(Of ChildClass)
        Get
            Return m_Children
        End Get
        Set
            m_Children = Value
        End Set
    End Property
    Private m_Children As ICollection(Of ChildClass)

    Public Sub New()
        Children = New HashSet(Of ChildClass)() From { _
            New ChildClass() _
        }
    End Sub
End Class

Private Function CopyEntity(Of T As {Class, New})(entity As T) As T
    Dim copy As New T()
    ' actual copying omitted here
    ' for testing only the return type matters
    Return copy
End Function

Private Sub Test()
    Dim [myClass] As New [MyClass]()
    Dim children As dynamic = GetType([MyClass]).GetProperty("Children").GetValue([myClass])
    Dim child As dynamic = Enumerable.ElementAt(children, 0)
    Dim copy As dynamic = CopyEntity(child)
    ' copy is of type ChildClass
End Sub

Dim en = ctx.Entry(clone)

dilkonika wrote:

and this code is not using CTypeDynamic.

Public Class ChildClass
End Class

Public Class SomeClass
    Public Property Children As ICollection(Of ChildClass) = New HashSet(Of ChildClass)
End Class

Public Function CopyEntity(Of T As {Class, New})(entity As T) As T
    Dim clone As New T()
    Return clone
End Function

Sub Main()
    Dim someClass = New SomeClass
    someClass.Children.Add(New ChildClass)

    Dim el = Enumerable.ElementAt(CallByName(someClass, "Children", CallType.Get), 0)

    Dim elcopy = CopyEntity(el)   REM without CTypeDynamic. doesn't work. (elcopy is Object)

    Dim el1 = CType(el, ChildClass)
    Dim el1copy = CopyEntity(el1) REM works (el1copy is ChildClass)

    Dim el2 = CTypeDynamic(Of ChildClass)(el)
    Dim el2copy = CopyEntity(el2) REM works (el2copy is ChildClass)

    Dim el3 = CTypeDynamic(el, GetType(ChildClass))
    Dim el3copy = CopyEntity(el3) REM doesn't work (el3copy is Object)
End Sub

Quote:

and on my vb.net code , the error came up on the line :
Dim en = ctx.Entry(clone)
and you don't have a such line in your code.

dilkonika wrote:

Also I try to implement your version with reflection , but I can't make it work on vb.net ? can you provide some more
help ?

class Program
{
    class ChildClass
    { }

    class SomeClass
    {
        public ICollection<ChildClass> Children { get; set; }

        public SomeClass()
        {
            Children = new HashSet<ChildClass>() { new ChildClass() };
        }
    }

    public static T CopyEntity<T>(T entity)
        where T : class, new()
    {
        T copy = new T();
        return copy;
    }

    static void Main(string[] args)
    {
        SomeClass someClass = new SomeClass();

        dynamic children = typeof(SomeClass).GetProperty("Children").GetValue(someClass);
        object child = Enumerable.ElementAt(children, 0);

        // if CopyEntity would be not a static method, BindingFlags.Instance
        // would have to be used, instead of BindingFlags.Static 
        MethodInfo mi = typeof(Program).GetMethod("CopyEntity", BindingFlags.Static | BindingFlags.Public);
        mi = mi.MakeGenericMethod(new Type[] { /* +typeof(YourContext) */ child.GetType() /* +typeof(bool) */ });

        // if CopyEntity would be not a static method, the first argument
        // to Invoke would have to be the class-instance on which to invoke
        // CopyEntity, instead of null
        object clone = mi.Invoke(null, new object[] { /* +ctx */ child /* +copyKeys */ });
        // -> clone is of type ChildClass
    }
}

Dim clone as New(T)

Dim clone = Activator.CreateInstance(entity.GetType())

dilkonika wrote:

Dim clone = Activator.CreateInstance(entity.GetType())

dilkonika wrote:

Thank you for your help.

Partial Public Class Myobject
  Public Property id As Integer
  Public property name as string
  Public Overridable Property Child_list As ICollection(Of Child_list) = New HashSet(Of Child_list) 
 End Class

Partial Public Class Child_list
    Public Property id As Integer
    Public Property date1 as DateTime
    Public Property quantity as Integer
    Public Property ParentID as integer
    Public Overridable Property MyObj1 As MyObject
End Class 

• Move the SetValue(..)-line back to where it was.
• Put an EdmScalarPropertyAttribute on the name-property of the Myobject-class and on all properties of the Child_list-class (except id and ParentID) like so:
  VB

  <EdmScalarProperty()>
  Public property name as string

• In CloneEntityHelper(..), change the string "EntityCollection`1" to "ICollection`1".
• If you want to have children of children copied (to an arbitrary depth), set the Children-property of your IncludeEntity-instance to the same IncludeEntity-instance.
• If you have to initialize id yourself, you will have to set it for Myobjects, Child_lists and potentially further nested objects, after the call to CloneEntity(..).
• Because of the self-referencing through ParentID you will have to set ParentID for all children (and potentially children of children) to their respective parent's id after the call to CloneEntity(..) (in any case).

Cloning by Reflection uses Activator.CreateInstance to create a new object of the same type, then performs a shallow copy of each field using Reflection. The advantage of this method is it's automated and does not need to be adjusted when members are added or removed from the object. Also, it can be written to provide a deep copy. The disadvantage is it uses Reflection, which is slower and not allowed in partial trust environments.

dilkonika wrote:

On your link in the clone with reflection section , contains just words.

<pre>  <Extension> _
    Public Sub CopyTo(Of T)(copyFrom As T, copyTo__1 As T, copyParentProperties As Boolean)
        Dim props As PropertyInfo()
        If copyParentProperties Then
            props = GetType(T).GetProperties()
        Else
            props = GetType(T).GetProperties(BindingFlags.[Public] Or BindingFlags.Instance Or BindingFlags.DeclaredOnly)
        End If
        Dim i As Integer = 0
        While i < props.Length
            Dim propertyValue = copyFrom.[GetType]().GetProperty(props(i).Name).GetValue(copyFrom, Nothing)
            copyTo__1.[GetType]().GetProperty(props(i).Name).SetValue(copyTo__1, propertyValue, Nothing)
            System.Math.Max(System.Threading.Interlocked.Increment(i), i - 1)
        End While
    End Sub

newitm = New Myobject
currentobj.CopyTo(newitm, False)
context.MyObjects.Add(Newitm)
context.savechanges

An unhandled exception of type 'System.InvalidOperationException' occurred in System.Core.dll

Additional information: Collection was modified; enumeration operation may not execute.

dilkonika wrote:

there are many articles on internet that suggest avoid ICloneable because of Shallow/Deep confusion.

dilkonika wrote:

An unhandled exception of type 'System.InvalidOperationException' occurred in System.Core.dll
Additional information: Collection was modified; enumeration operation may not execute.

newitm = New Myobject
currentobj.CopyTo(newitm, False)
context.MyObjects.Add(Newitm)
context.savechanges

newitm = New Myobject
context.MyObjects.Add(newitm)
currentobj.CopyTo(newitm, False)
context.savechanges