VB.NET;隨機生成列表的索引錯誤

我的目標是創建一個特定大小的列表並從該列表中隨機選擇3個點。一旦選擇了一個點，它將從列表中刪除，因此它不會再被選中。 我的問題是調試器說我有一個索引超出列表的範圍。我對VB.NET比較陌生，但對VBA非常有經驗。預先感謝您的幫助。VB.NET;隨機生成列表的索引錯誤

Private Sub Analyze_Click(ByVal Sender As System.Object, ByVal e As System.EventArgs) Handles Analyze_Image.Click 

    Dim i As Long, j As Long, k As Long, Image_Width As Long, Image_Height As Long, Pixel_Count As Long, Pixel As Long 
    Dim My_Image As Image 
    Dim RandomClass As New Random() 
    Dim RandomIndex_1 As Long, RandomIndex_2 As Long, RandomIndex_3 As Long 
    Dim P1 As Point, P2 As Point, P3 As Point 

    My_Image = My_PictureBox.Image 
    Image_Width = My_Image.Width 
    Image_Height = My_Image.Height 
    Pixel_Count = Image_Width * Image_Height 

    Dim Numbers = Enumerable.Range(0, Pixel_Count + 1).ToList() 

    For Pixel = 1 To Pixel_Count 
     RandomIndex_1 = RandomClass.Next(0, Numbers.Count) 
     Numbers.RemoveAt(RandomIndex_1) 
     RandomIndex_2 = RandomClass.Next(0, Numbers.Count) 
     Numbers.RemoveAt(RandomIndex_2) 
     RandomIndex_3 = RandomClass.Next(0, Numbers.Count) 
     Numbers.RemoveAt(RandomIndex_3) 

     i = Numbers(RandomIndex_1) 
     j = Numbers(RandomIndex_2) 
     k = Numbers(RandomIndex_3) 

     If i Mod Image_Width = 0 Then 
      P1.X = Image_Width 
     Else 
      P1.X = i Mod Image_Width 
     End If 
     If j Mod Image_Width = 0 Then 
      P2.X = Image_Width 
     Else 
      P2.X = j Mod Image_Width 
     End If 
     If k Mod Image_Width = 0 Then 
      P3.X = Image_Width 
     Else 
      P3.X = k Mod Image_Width 
     End If 
     If ((i - i Mod Image_Width)/Image_Width) + 1 = Image_Height + 1 Then 
      P1.Y = Image_Height 
     Else 
      P1.Y = ((i - i Mod Image_Width)/Image_Width) + 1 
     End If 
     If ((j - j Mod Image_Width)/Image_Width) + 1 = Image_Height + 1 Then 
      P2.Y = Image_Height 
     Else 
      P2.Y = ((j - j Mod Image_Width)/Image_Width) + 1 
     End If 
     If ((k - k Mod Image_Width)/Image_Width) + 1 = Image_Height + 1 Then 
      P3.Y = Image_Height 
     Else 
      P3.Y = ((k - k Mod Image_Width)/Image_Width) + 1 
     End If 
    Next 

End Sub

來源

2016-07-14 senuba91

它可能會有助於表明哪一行拋出異常，但它看起來像你來回移除項目列表（'Numbers.RemoveAt（RandomIndex_1）'），然後嘗試讀取它們（'i = Numbers（RandomIndex_1）'）。 – Mark

它也看起來像你需要'數字'列表中的'3 * Pixel_Count'項目？ – Mark

令人驚訝的簡單修復，我不知道我的大腦今天在哪裏。進行了這兩項變更，現在正在開展工作。謝謝！ – senuba91

除了對問題的意見，您可以通過使用數字的隨機排序堆有所簡化邏輯（但是，見this question了大約更好的方法來改組列表的討論）：

Dim Numbers = New Stack(
    Enumerable.Range(0, 3 * Pixel_Count) _ 
     .OrderBy(Function(i) RandomClass.Next()) _ 
     .ToList() 
)

你的環路，則可以只彈出數出棧：

For Pixel = 1 To Pixel_Count 
    i = Numbers.Pop() 
    j = Numbers.Pop() 
    k = Numbers.Pop() 

    If i Mod Image_Width = 0 Then 
     '... etc. 
Next

來源

2016-07-14 17:06:20 Mark

VB.NET;隨機生成列表的索引錯誤

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