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There's a free extension you can download here that lets you duplicate lines without replacing the clipboard contents.
By default its bound to Alt + D, but you can change it to anything you want by going to Tools->Options->Environment->Keyboard. Type "Duplicate" in the search box and look for "Edit.DuplicateSelection" and edit the shortcut to whatever you want. I prefer Ctrl + D to be consistent with other editors.
If you like eclipse style line (or block) duplicating using CTRL+ALT+UP or CTRL+UP+DOWN, below I post macros for this purpose:
Imports System
Imports EnvDTE
Imports EnvDTE80
Imports System.Diagnostics
Public Module DuplicateLineModule
Sub DuplicateLineDown()
Dim selection As TextSelection = DTE.ActiveDocument.Selection
Dim lineNumber As Integer
Dim line As String
If selection.IsEmpty Then
selection.StartOfLine(0)
selection.EndOfLine(True)
Else
Dim top As Integer = selection.TopLine
Dim bottom As Integer = selection.BottomLine
selection.MoveToDisplayColumn(top, 0)
selection.StartOfLine(0)
selection.MoveToDisplayColumn(bottom, 0, True)
selection.EndOfLine(True)
End If
lineNumber = selection.TopLine
line = selection.Text
selection.MoveToDisplayColumn(selection.BottomLine, 0)
selection.EndOfLine()
selection.Insert(vbNewLine & line)
End Sub
Sub DuplicateLineUp()
Dim selection As TextSelection = DTE.ActiveDocument.Selection
Dim lineNumber As Integer
Dim line As String
If selection.IsEmpty Then
selection.StartOfLine(0)
selection.EndOfLine(True)
Else
Dim top As Integer = selection.TopLine
Dim bottom As Integer = selection.BottomLine
selection.MoveToDisplayColumn(top, 0)
selection.StartOfLine(0)
selection.MoveToDisplayColumn(bottom, 0, True)
selection.EndOfLine(True)
End If
lineNumber = selection.BottomLine
line = selection.Text
selection.MoveToDisplayColumn(selection.BottomLine, 0)
selection.Insert(vbNewLine & line)
selection.MoveToDisplayColumn(lineNumber, 0)