Update DoDragDrop sample to make code more readable

[Tanya-Solyanik]

Summary

1. removed redundant namespace names for included namespaces, i.e. System.Windows.Forms
2. removed allocations of event handler delegates when adding event handlers
3. re-formatted a couple of long lines.

This code builds and runs on .NET Core and .NET Framework

[opbld34]

Docs Build status updates of commit 6a408be:

✅ Validation status: passed

File	Status	Preview URL	Details
samples/snippets/csharp/VS_Snippets_Winforms/System.Windows.Forms.Control.DoDragDrop/CS/form1.cs	✅Succeeded	View

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[opbld34]

Docs Build status updates of commit 380a1cc:

✅ Validation status: passed

File	Status	Preview URL	Details
samples/snippets/csharp/VS_Snippets_Winforms/System.Windows.Forms.Control.DoDragDrop/CS/form1.cs	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching in the Docs contributor and Admin Guide
• See the frequently asked questions
• Post your question in the Docs support channel

[opbld33]

Docs Build status updates of commit 5f4a2ae:

✅ Validation status: passed

File	Status	Preview URL	Details
samples/snippets/csharp/VS_Snippets_Winforms/System.Windows.Forms.Control.DoDragDrop/CS/form1.cs	✅Succeeded	View
samples/snippets/visualbasic/VS_Snippets_Winforms/System.Windows.Forms.Control.DoDragDrop/VB/form1.vb	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching in the Docs contributor and Admin Guide
• See the frequently asked questions
• Post your question in the Docs support channel

[gewarren]

LGTM

[Tanya-Solyanik]

Thanks!