Can't create instance of 'classname'

See more:

WPF

In the below code

<y:base x:Name="baseclass" x:Key="basetest"/>

this line prompting error like "Can't create instance of 'base'".

base.vb

Imports Tool2DLL
Public Class base
    Inherits WpfBaseToolBar   
End Class

In the above code, Tool2DLL is the dll we created and wpfbasetoolbar is the class which in the DLL

MainWindow.xaml

<Window x:Class="MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:y="clr-namespace:WpfApplication1" 
    xmlns:y1="clr-namespace:Tool2DLL;assembly=WpfControlLibrary1" 
    Height="350" Width="525">
    <Window.Resources>
        <y:base x:Name="baseclass" x:Key="basetest"/>
     </Window.Resources>
    <Grid>
          
    </Grid>
</Window>

How to solve the error. Any idea would be appriciable

Thanks & Regards
jai