DragDrop with TextBox no longer sets data type to StringFormat

The code from the .NET Framework WPF walkthrough about drag-drop, it doesn’t work on .NET 5/Core 3.1: https://docs.microsoft.com/en-us/dotnet/desktop/wpf/advanced/walkthrough-enabling-drag-and-drop-on-a-user-control?view=netframeworkdesktop-4.8

Specifically it’s this check:

if (e.Data.GetDataPresent(DataFormats.StringFormat))

In .NET Framework the drag-drop operation is initiated from a textbox creates a the data object of type DataFormats.StringFormat.

In .NET 5/Core 3.1, the data object generated is DataFormats.Text

Reported in dotnet/docs-desktop#160

[adegeo]

Tagging @einarstokke and @rubend30 for notifications

[miloush]

This is happening because of https://github.com/dotnet/wpf/commit/875b508196b1c69bf930ee676ee9aa5d594c32f7:

The last parameter, autoConvert is true by default on .NET Framework (except for DataFormats.ApplicationTrust):

https://referencesource.microsoft.com/#PresentationFramework/src/Framework/System/Windows/Documents/TextEditorCopyPaste.cs,822

This almost looks like an oversight during the broad commit to me, since users can get SystemFormat from Clipboard.GetDataObject().GetFormats() after setting string even in .NET Core.

That said, the documentation could probably be changed to just use UnicodeText.