WinForms Custom Controls
https://www.codeproject.com/Articles/5015/Validating-Edit-Controls
https://www.codeproject.com/Articles/1425/Validating-Edit-Controls
https://www.codeproject.com/Articles/806/A-Validating-Edit-Control
User Input Validation in Windows Forms
https://docs.microsoft.com/en-us/dotnet/framework/winforms/user-input-validation-in-windows-forms
Extending Windows Forms with a Custom Validation Component Library
https://msdn.microsoft.com/en-us/library/ms950965.aspx
Extend the Textbox Control to Validate Against Regular Expressions
https://www.codeproject.com/Articles/13922/Validate-user-input-in-Windows-Forms
https://www.codeproject.com/Articles/10093/Validators-for-Windows-Forms-ValidationProvider-Co
http://blog.scosby.com/post/2010/02/11/Validation-in-Windows-Forms.aspx
Source code
https://github.com/IgnaceMaes/MaterialSkin
Some Controls written in C# inherit from TextBox
https://github.com/smx-smx/open-sauce
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