Google's Material Design in XAML & WPF, for C# & VB.Net.
You can use Material Design for WPF: https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit
NOTE: The number of mentions on this list indicates mentions on common posts plus user suggested alternatives. Hence, a higher number means a more popular project.
How to design GUI ?
1 project | reddit.com/r/csharp | 1 Jul 2022
How do you make a dropdown box with custom controls?
1 project | reddit.com/r/csharp | 17 May 2022
WPF GUI that works like Bootstrap textbox design?
1 project | reddit.com/r/csharp | 9 Nov 2021
Finally finished a "real" project
2 projects | reddit.com/r/csharp | 16 Jun 2021
What is your opinion about WIN FORMS?
1 project | reddit.com/r/csharp | 7 Jun 2021