Need some help with wpf:?

Question

WPF

the program is not mine, I found it on the Internet, I wanted to look at it better, but the mainwindow window is not shown, it
gives an error: color picker doesn't exist in the namespace schemas.xceed.com/wpf/xaml/toolkit

<Grid Grid.Row="0"  >
<xctk:ColorPicker x:Name="colorBorderPicker" HorizontalAlignment="Center" Width="40" Margin="33,0,33.4,10" Height="22" VerticalAlignment="Bottom" SelectedColorChanged="colorBorderPicker_SelectedColorChanged"  />
</Grid>

Answer 1

xmlns:toolkit = " schemas.xceed.com/wpf/xaml/toolkit " - seems to be spelled out. check the libraries themselves in references
The easiest way to install is through the Package Manager Console with the command - Install-Package WPFToolkit
https://www.nuget.org/packages/WPFToolkit/

Answer 2

There are not enough libraries, or they are not included in the project links, fix it, or if this Xceed is rarely used there, then you can simply "throw it out" from everywhere and it will start.

Answer 3

The xctk namespace declaration is missing.
There should be something like this line:

<Window... xmlns:xctk="http://schemas.microsoft.com/expression/blend/2008" ../>