TextEdit.SelectedText
From Xojo Documentation
Property (As String )
aTextEdit.SelectedText = newStringValue
or
StringValue = aTextEdit.SelectedText
New in 2019r2
Supported for all project types and targets.
or
StringValue = aTextEdit.SelectedText
New in 2019r2
Supported for all project types and targets.
The currently selected text.
Example
This example places the selected text from a TextArea into a TextField.
TextArea1.SelectionStart = 0
TextArea1.SelectonLength = 10
TextField1.Value = TextArea1.SelectedText
TextArea1.SelectonLength = 10
TextField1.Value = TextArea1.SelectedText