从为选定 wpf combobox 值绑定的属性中获取 null

Question

I have class DimensionType, it has properties Name, Id, etc. I constructed Property in my ViewModel = "dimStyleId" to retrieve selected form ComboBox. I am getting null in this property although I checked it in TextBlock and get it.

<!--Dimension Type Combobox-->
        <ComboBox x:Name="DimensionType" 
                  ItemsSource="{Binding  dimTypes , Mode=TwoWay}" 
                  SelectedValue="{Binding dimStyleId , Mode=TwoWay}"
                  SelectedValuePath="DimensionType"
                  DisplayMemberPath="Name"
                  Padding="3"  />

and here is my VM Class

 public class GridsDimViewModel : INotifyPropertyChanged
    {
        public ElementId dimensionType;

        private ElementId _dimStyleId { get; set; }
        public ElementId dimStyleId
        {
            get
            {
               return _dimStyleId;
            }
            set
            {
                if (_dimStyleId != value)
                {
                    _dimStyleId = value;
                    NotifyPropertyChanged(nameof(dimStyleId));
                }
                

            }
        }
}

and here is my check textbox which gets the id in it

                <TextBlock Text="{Binding dimStyleId}" 
                           Padding="3" />

Answer 1

Swap

SelectedValuePath="DimensionType"

to

SelectedValuePath="Id"