Checkbox from ComboBoxItem is binded to Boolean in Class. How to get every Boolean from every single Item?

Sorry for my lacking of English and take in mind I just startet with WPF, so it might not even be the prettiest way to do this.

I tried to remove every Item where the Checkbox is Checked but I have Problems to point toward the Checkbox. So I tried to point toward a Boolean within a Class. But there are also Problems. Then I surrendered and came here.

Any Help is appreciated.

My Button who should delete a certain Item, with a checked checkbox, from a list looks like this.

private void DeleteComboBoxItem_Click(object sender, RoutedEventArgs e)
        {
            for (int i = 0; i < ComboBoxName.Items.Count; i++)
            {
                if (ComboBoxName.Item.Contains((CheckBox).Equals(True))) <--- Have Problems here.
                {
                    List.RemoveAt(i);
                }
            }
        }

Only the Name of the Cat is within the List - I have a formula where I can add cat names.

I have a ComboBox with the following template:

<ComboBox x:Name="ComboBoxName">
     <ComboBox.ItemTemplate>
           <DataTemplate>
                <Grid HorizontalAlignment="Stretch">
                     <Grid.ColumnDefinitions>
                         <ColumnDefinition Width="Auto"/>
                         <ColumnDefinition Width="*"/>
                     </Grid.ColumnDefinitions>
                     <CheckBox Grid.Column="0" IsChecked="{Binding b_CheckBox}" VerticalContentAlignment="Center"/>
                     <TextBlock Grid.Column="1" Text="{Binding tb_Name}" />
                </Grid>
           </DataTemplate>
     </ComboBox.ItemTemplate>
</ComboBox>

And a class that looks something like that.

public class Cat 
{
public bool b_Checkbox {get; set;}
public string tb_Name {get; set;}
}

Hope you can Help me.