VB.NET 无法旋转图像中的字符串

我想旋转图像中的字符串，但做不到，有人能帮我吗，我试过了"drawformat"；但它不旋转，只是居中。我想在"情况"中旋转B；K-11"；90度、B 45度和C 90度；K-21〃；或者类似的东西。非常感谢。

Public Class ImageRebartoRevit
Private Sub OK_Click(sender As Object, e As EventArgs) Handles OK.Click
xuat_shapcode_revit(ShapeCode.Text)
End Sub
Function xuat_shapcode_revit(shapecode As String) As Boolean
Dim newBitmap As Bitmap
newBitmap = New Bitmap("C:UsersADMINDesktopIMG" + shapecode + ".png")
Dim Graphics As Graphics
Dim A As String = L1.Text
Dim B As String = L2.Text
Dim C As String = L3.Text        
Graphics = Graphics.FromImage(newBitmap)
Dim drawformat As New StringFormat()
drawformat.Alignment = StringAlignment.Center
Select Case shapecode
Case "K-00"
Graphics.DrawString(A, New Font("Arial", 50, FontStyle.Regular), New SolidBrush(Color.Black), New Point(470, 90), drawformat)
Case "K-11"
Graphics.DrawString(A.ToString, New Font("Arial", 50, FontStyle.Regular), New SolidBrush(Color.Black), New Point(843, 128), drawformat)
Graphics.DrawString(B.ToString, New Font("Arial", 50, FontStyle.Regular), New SolidBrush(Color.Black), New Point(457, 124), drawformat)
Case "K-21"
Graphics.DrawString(A.ToString, New Font("Arial", 50, FontStyle.Regular), New SolidBrush(Color.Black), New Point(75, 139), drawformat)
Graphics.DrawString(B.ToString, New Font("Arial", 50, FontStyle.Regular), New SolidBrush(Color.Black), New Point(467, 124), drawformat)
Graphics.DrawString(C.ToString, New Font("Arial", 50, FontStyle.Regular), New SolidBrush(Color.Black), New Point(859, 139), drawformat)

End Select
newBitmap.Save("C:UsersADMINDesktopIMGout_put_" + shapecode + ".bmp", System.Drawing.Imaging.ImageFormat.Jpeg)
Return True
End Function
End Class