如何查看图片框中的图像？

Question

我已使用以下代码绘制所需的内容，但是当我使用此代码时，看不到我在图片框上设置的图像。我该怎么办才能在图片框上绘制图像？请帮助我。

Public Class Form1
Dim draw As Boolean
Dim DrawColor As Color = Color.Black
Dim DrawSize As Integer = 6
Dim bmp As Bitmap




Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
    cbxSize.SelectedIndex = 2
    bmp = New Bitmap(pbDraw.Width, pbDraw.Height)
    pbDraw.Image = bmp
    Dim down = False

End Sub
Private Sub PaintBrush(X As Integer, Y As Integer)
    Using g As Graphics = Graphics.FromImage(pbDraw.Image)
        g.FillRectangle(New SolidBrush(DrawColor), New Rectangle(X, Y, DrawSize, DrawSize))

    End Using
    pbDraw.Refresh()

End Sub

绘画事件

Private Sub pbtest_MouseDown(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles pbDraw.MouseDown
    draw = True
    PaintBrush(e.X, e.Y)
End Sub

Private Sub pbtest_MouseMove(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles pbDraw.MouseMove
    If draw = True Then
        PaintBrush(e.X, e.Y)
    End If
End Sub

Private Sub pbtest_MouseUp(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles pbDraw.MouseUp
    draw = False
End Sub

请帮助我