Question

我有这段代码：

Public Class Form1
Private _Previous As System.Nullable(Of Point) = Nothing
Private Sub pictureBox1_MouseDown(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseDown
    _Previous = e.Location
    pictureBox1_MouseMove(sender, e)
End Sub

Private Sub PictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove
    Dim Marker As Integer
    Marker = Lst_Markers.SelectedIndex + 1
    If _Previous IsNot Nothing Then
        For i As Integer = 0 To Marker
            Dim bmp As New Bitmap(PictureBox1.Width, PictureBox1.Height)
            PictureBox1.Image = bmp
        Next
        Select Case Lst_Markers

            Case 1
                Using g As Graphics = Graphics.FromImage(PictureBox1.Image)
                    g.FillEllipse(Brushes.Red, e.X, e.Y, 10, 10)
                End Using
            Case 2

                Using g As Graphics = Graphics.FromImage(PictureBox1.Image)
                    g.FillEllipse(Brushes.Yellow, e.X, e.Y, 10, 10)
                End Using
            Case 3

                Using g As Graphics = Graphics.FromImage(PictureBox1.Image)
                    g.FillEllipse(Brushes.Green, e.X, e.Y, 10, 10)
                End Using
            Case 4

                Using g As Graphics = Graphics.FromImage(PictureBox1.Image)
                    g.FillEllipse(Brushes.Blue, e.X, e.Y, 10, 10)
                End Using
            Case Else
                MsgBox("Select a marker")
        End Select
        PictureBox1.Invalidate()
        _Previous = e.Location
    End If
End Sub

Private Sub pictureBox1_MouseUp(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseUp
    _Previous = Nothing
End Sub
End Class

但是我在问题标题中收到错误。问题是“案例1”，“案例2”，“案例3”，“案例4”的陈述，我想知道我做错了什么，我认为问题在于我的问题 Marker = Lst_Markers.SelectedIndex + 1 这是对的吗？

Answer 1

您的意思是Select Case Marker而不是Select Case Lst_Markers吗？

您无法将Lst_Markers与Case语句中的整数进行比较 - 将控件与整数进行比较是没有意义的。如果您想比较所选索引，Marker似乎就是您要比较的内容。

Answer 2

尝试在select语句中使用整数变量。

Select Case Marker

而不是：

Select Case Lst_Markers

Answer 3

LST_Markers是ListBox，无法与整数进行比较。我认为你的案例陈述中的意思是LST_Markers.selectedIndex。

Answer 4

我无法肯定地说，因为Lst_Markers没有在您引用的代码中定义，但是如果出现错误，则会出现Lst_Markers是Listbox。列表框不是整数，那么Select Case Lst_Markers是什么意思？我不认为这是你想要选择的变量。（你可能意味着马克。）

Answer 5

为什么不使用：Select Case Lst_Markers.SelectedIndex + 1

一起摆脱Marker

但出于好奇，你们每个循环的功能是什么？

    For i As Integer = 0 To Marker
        Dim bmp As New Bitmap(PictureBox1.Width, PictureBox1.Height)
        PictureBox1.Image = bmp
    Next

我真的没有看到这样做的几点，例如：
如果你选择绿色，直到运行5次，如果你选择红色，那么只运行两次。

我测试了你的代码，没有For For look，只有两行：

    Dim bmp As New Bitmap(PictureBox1.Width, PictureBox1.Height)
    PictureBox1.Image = bmp

代码似乎与在每个循环中的代码相同。

没有为类型'System.Windows.Forms.Listbox'和'Integer'定义Operator'='

5 个答案: