Alpha transparency support in WinForms controls (TextBox vs Button)

[umanagarajan12]

I am evaluating support for transparency and alpha colors in WinForms controls and have observed inconsistent behavior between controls. Some controls appear to accept colors created with Color.FromArgb(alpha, r, g, b), while TextBox rejects the same color assignment.

Example
textBox3.BackColor = Color.FromArgb(128, 243, 243, 243);
Observed Behavior
Assigning an alpha color to TextBox.BackColor throws the following exception:

System.ArgumentException: 'Control does not support transparent background colors.'

Questions for Microsoft

1. Is the System.ArgumentException ("Control does not support transparent background colors") the expected behavior when assigning a color with an alpha value (A < 255) to a TextBox?
2. Why do some WinForms controls appear to accept alpha-transparent colors, while TextBox rejects them?
3. Is this limitation imposed by the WinForms framework, or by the underlying native Win32 EDIT control used by TextBox?
4. Is there official Microsoft documentation that explicitly states whether TextBox and other standard WinForms controls support alpha-transparent background colors?
5. Is there a documented list or support matrix indicating which WinForms controls do and do not support transparent or alpha-transparent background colors?
6. For controls that do not support alpha transparency (for example, TextBox), what is the Microsoft-recommended approach for achieving transparent or semi-transparent visual effects?
   • Custom-painted controls
   • Owner-drawn controls
   • Layered windows
   • Custom rendering techniques
   • Any other recommended approach
7. What is the recommended way to implement semi-transparent backgrounds for text input controls while preserving standard WinForms behavior, accessibility, and performance?
8. Are there any plans or ongoing efforts to provide more consistent transparency support across WinForms controls in future releases?