cast the Parent object to Child object in C#

Question

Hi i want to cast the Parent object to Child object in C#

public class Parent {     public string FirstName {get; set;}     public string LastName {get; set;}     public string City {get; set;} }  public class Child : Parent {     public string PhoneNumber {get; set;}     public string MobileNumber {get; set;} } 

now the scenario is is a list of parent object and i want to generate list of child object so that i can have extended information

List<Parent> lstParent; List<Child> lstChild = new List<Child>();  foreach(var obj in lstParent) {     lstChild.add((Child)obj); } 

as child class inherited parent class so the child class already have the parent class member i just want to fill them automatically so that i can populate datamember of child class

Answer 1

I do so (this is just an example):

using System.Reflection;  public class DefaultObject {     ... }  public class ExtendedObject : DefaultObject {     ....     public DefaultObject Parent { get; set; }      public ExtendedObject() {}     public ExtendedObject(DefaultObject parent)     {         Parent = parent;          foreach (PropertyInfo prop in parent.GetType().GetProperties())             GetType().GetProperty(prop.Name).SetValue(this, prop.GetValue(parent, null), null);     } } 

Using:

DefaultObject default = new DefaultObject { /* propery initialization */ }; ExtendedObject extended = new ExtendedObject(default); // now all properties of extended are initialized by values of default properties. MessageBox.Show(extended.Parent.ToString()); // now you can get reference to parent object 

Answer 2

If I understand your "I just want to fill them automatically" comment correctly, you want to create a new Child object that's populated with the values of the Parent, with default values for the new properties. Best way to do that is to create a constructor that copies the values:

public class Parent {    public string FirstName {get; set;}     public string LastName {get; set;}     public string City {get; set;} }  public class Child : Parent {     public string PhoneNumber {get; set;}     public string MobileNumber {get; set;}      public Child (Parent parentToCopy)     {         this.FirstName = parentToCopy.FirstName;         this.LastName = parentToCopy.LastName;         this.City = parentToCopy.City;          this.PhoneNumber = string.Empty; // Or any other default.         this.MobileNumber = string.Empty;     }  } 

Now you can use LINQ, like the answers above, to create a Child out of each Parent:

List<Child> lstChild = lstParent.Select(parent => new Child(parent)).ToList(); 

Note that this is very similar to @daryal's answer, but wraps the parent-to-child copying logic inside the constructor, rather than having it outside in the new Child() call.