Bind problem in C# WPF

Question

I have a WPF that is as follows:

 <ComboBox Name="comboBoxRemetente" VerticalContentAlignment="Center" Margin="5" Grid.ColumnSpan="20"
              ItemsSource ="{Binding Path=Lista, Mode = TwoWay}" 
              SelectedValue="{Binding Path=Model, Mode = TwoWay}"
              DisplayMemberPath="Remetente"
              IsSynchronizedWithCurrentItem="True"
              SelectedIndex="0"
    >
    </ComboBox>
<DataGrid Name="GridLista" 
                     Grid.ColumnSpan="20" 
                     Margin="5" 
                     Grid.RowSpan="11" 
                     Grid.Row="8"
                     CanUserAddRows="False"
                     CanUserReorderColumns="True"
                     AutoGenerateColumns="False" 
                     SelectionUnit="FullRow"
                     SelectionMode="Extended"
                     ItemsSource="{Binding Path=Lista}"
                     SelectedValue="{Binding Path=Model, Mode = TwoWay}"
                     IsReadOnly="True"
              >

So, when I start the screen I load the FATHER list and it fills the fields almost everything correctly. My problem is:

I got this combobox:

<ComboBox Name="comboBoxCartao" Grid.Row="7" Grid.ColumnSpan="8" VerticalContentAlignment="Center" Padding="0" Margin="5" Grid.Column="2"
              ItemsSource ="{Binding Path=CartaoBean.Lista, Mode = TwoWay}" 
              SelectedValue="{Binding Path=Model.Cartao, Mode = TwoWay}"
              DisplayMemberPath="ToComboBox"
              IsSynchronizedWithCurrentItem="True"
              SelectedIndex="0"
    >
    </ComboBox>

This last combobox carries a list of CHILDREN, I have set this one a son, so I need that when selecting a FATHER, he also select the SON in this combobox, could you help me where I am missing? rs

Hash Method of the Card:

public override bool Equals(object obj)
    {
        var cart = obj as CartaoPostagemModel;
        if (cart == null) return false;
        return cart.Cartao == this.Cartao;
    }

    public override int GetHashCode()
    {
        unchecked // Overflow is fine, just wrap
        {
            int hash = 17;
            // Suitable nullity checks etc, of course :)
            hash = hash * 23 + Id.GetHashCode();
            hash = hash * 23 + Cartao.GetHashCode();
            hash = hash * 23 + Contrato.GetHashCode();
            return hash;
        }
    }

Answer 1

Apparently, your problem is because of the use of Binding by object. C# (not a WPF issue) does not know when two objects are equal if they are not the same instance. To solve this, you can:

1 - Overwrite the Equals method

class Cartao {

        public override bool Equals(object obj)
        {
            var cart = obj as Cartao;

            if (cart == null) return false;
            return cart.Numero == this.Numero;

        }
}

2 - Swap Binding for a key field. Well, in this case it is a little more work, because you need to use the key field and also change the instance, if you use instance in the Rementente class, whenever the option is exchanged:

XAML

<ComboBox Name="comboBoxCartao" Grid.Row="7" Grid.ColumnSpan="8" VerticalContentAlignment="Center" Padding="0" Margin="5" Grid.Column="2"
              ItemsSource ="{Binding Path=CartaoBean.Lista, Mode = TwoWay}"              
              SelectedValuePath="Cartao_Id"           
              SelectedItem="{Binding Path=Model.CartaoView, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
              SelectedValue="{Binding Path=Model.Cartao_Id, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
              DisplayMemberPath="ToComboBox"
              IsSynchronizedWithCurrentItem="True"
              SelectedIndex="0">
</ComboBox>       

C#

private CartaoViewData CartaoView;

public CartaoViewData CartaoView
{
    get { return CartaoView; }
    set
    {
        CartaoView = value;
        base.OnPropertyChanged(nameof(CartaoView));

        if (value == null)
        {
            Cartao_Id = null;
        }
        else
        {
            Cartao_Id = value.Id;
        }

    }
}

public int? Cartao_Id
{
    get { return _CartaoId; }
    set
    {
        _CartaoId = value;
        base.OnPropertyChanged(nameof(Cartao_Id));
    }
}