Text selection for TextBlock And AutoSize for RichTextBox

When you use WPF to develop chat applications, you will find that you need to use the TextBlock control to display rich text and allow the user to select and copy text is a very common need, if you use TextBox to implement it lacks TextBlock's Inlines property, if you use RichTextBox to implement it lacks TextBlock's automatic width and height properties, I hope to add the function of the selection effect to TextBlock. RichTextBox adds automatic height and width