WPF 之InsertBefore 與 InsertAfter用

     在Blocks中插入某一個block，使用Document.Blocks.InsertBefore或者m_editor.Document.Blocks.InsertAfter,

public void InsertAfter(
    TextElementType previousSibling,
    TextElementType newItem
)

public void InsertBefore(
    TextElementType nextSibling,
    TextElementType newItem
)