.NET Framework 4.6 and 4.5
Assembly: PresentationFramework (in PresentationFramework.dll)
The following example illustrates the use of this property.
// Create a simple FlowDocument to serve as the content input for the construtor. FlowDocument flowDoc = new FlowDocument(new Paragraph(new Run("Simple FlowDocument"))); // After this constructor is called, the new RichTextBox rtb will contain flowDoc. RichTextBox rtb = new RichTextBox(flowDoc); // This call will select the entire contents of the RichTextBox. rtb.SelectAll(); // This call returns the current selection (which happens to be the entire contents // of the RichTextBox) as a TextSelection object. TextSelection currentSelection = rtb.Selection;