How to solve this ComboBox item setting problem? - combobox

Question

This code is not setting right value to the combobox. This is because, those are from different contexts.
In addition, in my actual problem, neither overloading == in nor overriding Equals() in MyClass is working as well.
Any alternative way?
How to solve this problem?
MyClass.cs
public class MyClass
{
public int ID { get; set; }
public string Name { get; set; }
public MyClass(int id, string name)
{
ID = id;
Name = name;
}
public static List<MyClass> Get()
{
return new List<MyClass>
{
new MyClass(2, "AAA"),
new MyClass(4, "BBB"),
new MyClass(5, "CCC"),
new MyClass(7, "DDD"),
new MyClass(10, "EEE")
};
}
}
ComboBoxForm.cs
public partial class ComboBoxForm : Form
{
public ComboBoxForm()
{
InitializeComponent();
}
private void Form1_Shown(object sender, EventArgs e)
{
LoadDataToComboBoxFromDatabase();
}
private void LoadDataToComboBoxFromDatabase()
{
comboBox1.Items.Clear();
List<MyClass> list = MyClass.Get();
foreach(MyClass mc in list)
{
comboBox1.Items.Add(mc);
}
comboBox1.DisplayMember = "Name";
comboBox1.ValueMember = "ID";
comboBox1.SelectedIndex = 0;
}
private void button1_Click(object sender, EventArgs e)
{
int ID = 5;//This is what I have.
comboBox1.SelectedItem = .............how?
}
}

Answer 1

I believe your Equals comparison may be incorrect. For NHibernate, I use the following Equals() method:
public static class EntityUtil
{
public static bool Equals(IEntity a, IEntity b)
{
// Transient entitys are never equal (unless they are ReferenceEquals)!
return
ReferenceEquals(a, b) || (
!((object)a == null || (object)b == null) &&
!(IsTransient(a) || IsTransient(b)) &&
NHibernateProxyHelper.GetClassWithoutInitializingProxy(a) == NHibernateProxyHelper.GetClassWithoutInitializingProxy(b) &&
a.Id.Equals(b.Id)
);
}
public static bool IsTransient(IEntity entity)
{
return entity.Id == 0;
}
}
I have defined this method in a separate helper class and use this in my entity:
public class Entity : IEquatable<Entity>, IEquatable<IEntity>
{
private int? _hashCode;
public virtual int Id { get; protected set; }
public override bool Equals(object obj)
{
return EntityUtil.Equals((IEntity)this, obj as IEntity);
}
public virtual bool Equals(Entity obj)
{
return EntityUtil.Equals((IEntity)this, (IEntity)obj);
}
public virtual bool Equals(IEntity obj)
{
return EntityUtil.Equals((IEntity)this, obj);
}
public static bool operator ==(Entity a, Entity b)
{
return EntityUtil.Equals((IEntity)a, (IEntity)b);
}
public static bool operator !=(Entity a, Entity b)
{
return !(a == b);
}
public override int GetHashCode()
{
// GetHashCode needs to return a stable value.
if (!_hashCode.HasValue)
{
_hashCode =
NHibernateProxyHelper.GetClassWithoutInitializingProxy(this).GetHashCode() ^
((IEntity)this).Id.GetHashCode();
}
return _hashCode.Value;
}
}
This is the suggested implementation for working with equality with NHibernate. Maybe this helps for you too.