開始用下面的方法:
Dim r As RichTextBox = RichTextBox1
Dim lines, iFirst, iLast As Int32
iFirst = r.GetLineFromCharIndex(r.GetCharIndexFromPosition(New Point(0, 0)))
iLast = r.GetLineFromCharIndex(r.GetCharIndexFromPosition(New Point(0, r.Height)))
lines = iLast - iFirst
MessageBox.Show(lines)
但發現不是很準確,如果滾動條在中間的時候纔是正確的行數,如果RichTextBox中沒有字符,或字符不多,沒有滾動條出現的時候就不對了,
下面的方法可以:
Dim g As Graphics
g = RichTextBox1.CreateGraphics()
lines = RichTextBox1.Height / g.MeasureString("test",RichTextBox1.Font).Height()
MessageBox.Show(lines)