This post originated from my previous question. In previous question, I was asking how to create a circular list box control. A list box, if scroll down to the last element and continue scroll down, it will appear first element; if scroll up to the first element and keep scroll up, it will appear last element. It looks like IPhone alarm setting function. Here is my solution.<\/p>\n
\npublic class CircularListBox : System.Windows.Forms.ListBox\n{\n private System.ComponentModel.Container components = null;\n const int WM_VSCROLL = 0x0115;\n const int WM_KEYDOWN = 0x0100;\n\n const int SB_LINEUP = 0x0000;\n const int SB_LINEDOWN = 0x0001;\n\n const int VK_DOWN = 0x0028;\n const int VK_UP = 0x0026;\n const int VK_NEXT = 0x0022;\n const int VK_PRIOR = 0x0021;\n\n public CircularListBox()\n {\n \/\/ This call is required by the Windows.Forms Form Designer.\n InitializeComponent();\n\n \/\/ TODO: Add any initialization after the InitializeComponent call\n\n }\n\n \/\/\/ \n \/\/\/ Clean up any resources being used.\n \/\/\/ <\/summary>\n protected override void Dispose(bool disposing)\n {\n if (disposing)\n {\n if (components != null)\n {\n components.Dispose();\n }\n }\n base.Dispose(disposing);\n }\n\n #region Component Designer generated code\n \/\/\/ \n \/\/\/ Required method for Designer support - do not modify \n \/\/\/ the contents of this method with the code editor.\n \/\/\/ <\/summary>\n private void InitializeComponent()\n {\n components = new System.ComponentModel.Container();\n }\n #endregion\n protected int offset = 0;\n\n public new int TopIndex\n {\n get { return (this.Items.Count + offset + base.TopIndex) % this.Items.Count; }\n set\n {\n if (value > this.Items.Count - 1)\n return;\n Message m = new Message();\n m.Msg = WM_KEYDOWN;\n m.WParam = (System.IntPtr)VK_DOWN;\n while (value != this.TopIndex)\n WndProc(ref m);\n }\n }\n\n protected override void WndProc(ref Message m)\n {\n if (m.Msg == WM_VSCROLL || m.Msg == WM_KEYDOWN)\n {\n if (this.SelectedIndex == -1)\n this.SelectedIndex = 0;\n\n switch ((int)m.WParam)\n {\n case VK_PRIOR:\n case VK_UP:\n case SB_LINEUP:\n if (this.SelectedIndex == 0)\n {\n offset = (this.Items.Count + offset - 1) % this.Items.Count;\n this.Items.Insert(0, this.Items[this.Items.Count - 1]);\n this.Items.RemoveAt(this.Items.Count - 1);\n this.SelectedIndex = 0;\n }\n else\n {\n this.SelectedIndex--;\n }\n break;\n case VK_DOWN:\n case SB_LINEDOWN:\n case VK_NEXT:\n if (this.SelectedIndex == this.Items.Count - 1)\n {\n offset = ++offset % this.Items.Count;\n this.Items.Add(this.Items[0]);\n this.Items.RemoveAt(0);\n this.SelectedIndex = this.Items.Count - 1;\n }\n else\n {\n this.SelectedIndex++;\n }\n break;\n default:\n base.WndProc(ref m);\n break;\n }\n }\n else\n base.WndProc(ref m);\n }\n}\n<\/pre>\n","protected":false},"excerpt":{"rendered":"This post originated from my previous question. In previous question, I was asking how to create a circular list box control. A list box, if scroll down to the last element and continue scroll down, it will appear first element; if scroll up to the first element and keep scroll up, it will appear last … Continue reading “Create customized .Net Component – CircularListBox in C#”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9,2],"tags":[],"class_list":["post-77","post","type-post","status-publish","format-standard","hentry","category-net","category-it"],"_links":{"self":[{"href":"https:\/\/nickdu.com\/index.php?rest_route=\/wp\/v2\/posts\/77","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nickdu.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nickdu.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nickdu.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/nickdu.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=77"}],"version-history":[{"count":0,"href":"https:\/\/nickdu.com\/index.php?rest_route=\/wp\/v2\/posts\/77\/revisions"}],"wp:attachment":[{"href":"https:\/\/nickdu.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=77"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nickdu.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=77"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nickdu.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=77"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}