Fix clipboard GetData() examples showing null instead of NotSupportedException

[Copilot]

Code examples incorrectly show GetData() returning null when it actually returns a NotSupportedException instance when BinaryFormatter deserialization is required but not enabled.

Changes

• C# ObsoletePatterns.cs: Update comments (lines 23, 34) and null check (line 35) to reflect exception-based behavior
• VB ObsoletePatterns.vb: Update comments (lines 19, 29) and null check (line 30) to reflect exception-based behavior

Context

The main documentation correctly states the behavior, but code examples contradict it:

// Current (incorrect):
object data = Clipboard.GetData("MyApp.Person");
// Always returns null on a custom object type
if (data != null) { /* ... */ }

// Should be:
object data = Clipboard.GetData("MyApp.Person");
// Returns NotSupportedException when BinaryFormatter is required but not enabled
if (data is not NotSupportedException) { /* ... */ }

These examples demonstrate obsolete patterns that developers should avoid, so accuracy is critical for proper migration guidance.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Some code examples still show null for Clipboard GetData when instead they return an exception</issue_title>
<issue_description>### Type of issue

Code doesn't work

Description

There was a behavior change from the time the article was written to when it was actually published. Some of the code examples still show, expect, or comment about null being returned when in fact it returns a NotSupportedException instance. These should be fixed.

Page URL

https://learn.microsoft.com/en-us/dotnet/desktop/winforms/migration/clipboard-dataobject-net10

Content source URL

https://github.com/dotnet/docs-desktop/blob/main/dotnet-desktop-guide/winforms/migration/clipboard-dataobject-net10.md

Document Version Independent Id

d7829387-6c41-1e77-8c93-113d49382167

Platform Id

54424045-aea6-3a25-8c01-9c53dc5840ca

Article author

@adegeo

Metadata

• ID: d7829387-6c41-1e77-8c93-113d49382167
• PlatformId: 54424045-aea6-3a25-8c01-9c53dc5840ca
• Service: dotnet-desktop
• Sub-service: winforms

Related Issues</issue_description>

Comments on the Issue (you are @copilot in this section)

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Examines an issue and develops a plan of action to address it.

• Fixes Some code examples still show null for Clipboard GetData when instead they return an exception #2146

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[adegeo]

@copilot this plan looks good. Perform the actions