Document KeyPreview exceptions and keyboard interception guidance for WinForms

[adegeo]

Fixes #2235

• Added "When KeyPreview is not enough" section to how-to-handle-forms.md covering preprocessing exceptions and a ProcessCmdKey override example.
• Added a quick decision guide table to overview.md for choosing the right keyboard interception API.
• Added "Form-level keyboard input limitations" section to overview.md with a cross-link to the new exceptions section.
• Fixed a punctuation artifact in the overview.md preprocessing table.
• Fixed incorrect WPF type reference in validation.md.
• Added a locale-sensitivity caution to the SendKeys example in how-to-simulate-events.md.
• Updated how-to-handle-forms snippets to use readable character literals instead of numeric char codes.

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Internal previews

📄 File	🔗 Preview link
dotnet-desktop-guide/winforms/input-keyboard/how-to-change-key-press.md	dotnet-desktop-guide/winforms/input-keyboard/how-to-change-key-press
dotnet-desktop-guide/winforms/input-keyboard/how-to-check-modifier-key.md	dotnet-desktop-guide/winforms/input-keyboard/how-to-check-modifier-key
dotnet-desktop-guide/winforms/input-keyboard/how-to-handle-forms.md	dotnet-desktop-guide/winforms/input-keyboard/how-to-handle-forms
dotnet-desktop-guide/winforms/input-keyboard/how-to-simulate-events.md	dotnet-desktop-guide/winforms/input-keyboard/how-to-simulate-events
dotnet-desktop-guide/winforms/input-keyboard/overview.md	dotnet-desktop-guide/winforms/input-keyboard/overview
dotnet-desktop-guide/winforms/input-keyboard/validation.md	dotnet-desktop-guide/winforms/input-keyboard/validation

[Copilot]

Pull request overview

This PR updates the Windows Forms keyboard input docs to better explain why KeyPreview doesn’t catch some keys (notably keys handled during preprocessing), and it refreshes related snippets and references.

Changes:

• Added a new “When KeyPreview is not enough” section that explains preprocessing exceptions and shows a ProcessCmdKey override example.
• Added a quick decision guide and a form-level limitations note to the keyboard input overview.
• Updated snippets (readability improvements, SendKeys sequences), plus fixed a WinForms/WPF type reference and refreshed dates.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
dotnet-desktop-guide/winforms/input-keyboard/validation.md	Fixes an incorrect WPF TextBox reference to the WinForms TextBox, and updates ms.date.
dotnet-desktop-guide/winforms/input-keyboard/overview.md	Adds a keyboard interception decision table, clarifies form-level limitations, and fixes a punctuation artifact.
dotnet-desktop-guide/winforms/input-keyboard/how-to-simulate-events.md	Adds a caution about locale-sensitive window title lookup.
dotnet-desktop-guide/winforms/input-keyboard/how-to-handle-forms.md	Adds a section explaining preprocessing exceptions and links to ProcessCmdKey examples.
dotnet-desktop-guide/winforms/input-keyboard/snippets/how-to-simulate-events/vb/projectvb.vbproj	Updates snippet project TFM to net10.0-windows.
dotnet-desktop-guide/winforms/input-keyboard/snippets/how-to-simulate-events/vb/Form1.vb	Updates SendKeys sequence to match the intended shortcut.
dotnet-desktop-guide/winforms/input-keyboard/snippets/how-to-simulate-events/csharp/project.csproj	Updates snippet project TFM to net10.0-windows.
dotnet-desktop-guide/winforms/input-keyboard/snippets/how-to-simulate-events/csharp/Form1.cs	Updates SendKeys sequence to match the intended shortcut.
dotnet-desktop-guide/winforms/input-keyboard/snippets/how-to-handle-forms/vb/projectvb.vbproj	Updates snippet project TFM to net10.0-windows.
dotnet-desktop-guide/winforms/input-keyboard/snippets/how-to-handle-forms/vb/Form1.vb	Improves digit detection/readability, and adds a ProcessCmdKey override snippet.
dotnet-desktop-guide/winforms/input-keyboard/snippets/how-to-handle-forms/csharp/project.csproj	Updates snippet project TFM to net10.0-windows.
dotnet-desktop-guide/winforms/input-keyboard/snippets/how-to-handle-forms/csharp/Form1.cs	Improves digit detection/readability, and adds a ProcessCmdKey override snippet.

[gewarren]

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[gewarren]

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