public partial class OrgSelect : UserControl
    {
...
        [
        Bindable(true),
        Category("Прикладные"),
        DefaultValue("Normal"),
        Description("Идентификатор организации"),
        ]
        public int orgID
        {
            get { return (int)GetValue(orgIDProperty); }
            set { SetValue(orgIDProperty, value); }
        }
        public static readonly DependencyProperty orgIDProperty =
            DependencyProperty.Register("orgID", typeof(int), typeof(OrgSelect), new FrameworkPropertyMetadata(0, ChangedorgID)
            {BindsTwoWayByDefault = true, DefaultUpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged});
        static void ChangedorgID(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            //(d as OrgSelect);
            ...
        }

...
}

<UserControl x:Class="Elcom.OrgSelect"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:elcom="clr-namespace:Elcom"
             mc:Ignorable="d" 
             d:DesignHeight="40" d:DesignWidth="600" 
             x:Name="ORGSEL">
    
    <UserControl.DataContext>
        <elcom:OrgOtdViewModel x:Name="orgotdviewmodel" iorgid="{Binding Path=orgID, ElementName=ORGSEL, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"/>
    </UserControl.DataContext>
....
</UserControl>