Unable to load DLL in the WPF-project

I do have a UserControl (works) which I would like to use in a WPF project. When I run the application I get following error

Unable to load DLL 'VCECLB.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)"

This is a C++ dll and if I add it under references it goes to the project folder like this:

I also add it in the output folder \bin\x64\Release but without success. What I am doing wrong here? Any feedback would be highly appreciated!

UPDATE:

The XAML for loading the UserControl looks like this:

<Window x:Class="WpfApplication1LL_Neu.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:lowLightGrab="clr-namespace:LowLightGrab;assembly=LowLightGrab"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <WindowsFormsHost Height="290" HorizontalAlignment="Left" Margin="16,10,0,0" Name="windowsFormsHost1" VerticalAlignment="Top" Width="475">
        <lowLightGrab:UserControl1/>
    </WindowsFormsHost>
</Grid>
</Window>

Thanks

Once added as reference it will be copied to output folder.

For design time you have to add in your Window:

xmlns:VCECLB="clr-namespace:VCECLB;assembly=VCECLB"