定义一个bool类型的变量,默认为FALSE的

 1 private bool BHaveBeenTip=false;
 2 private void label5_Click(object sender, EventArgs e)
 3         {
 4             var oFileBrowser = new FileBowser();
 5             if (oFileBrowser.ShowDialog() == DialogResult.OK)
 6             {
 7                 foreach (string fName in oFileBrowser.ListSelectedFile)
 8                 {
 9                         this.AddAttachment(fName, false, false);
10                 }
11                 bHasBeenTips = false;
12             }
13             oFileBrowser.Dispose();
14         }
15 
16 private void AddAttachment(string aFileName, bool aIsDelete, bool aIsLargeAttachment)
17 {
18             if (attachList.Exists(o => o.Equals(aFileName, StringComparison.OrdinalIgnoreCase)))
19             {
20                      if (!bHasBeenTips)     //此处省略了  if(!bHasBeenTips==true)
21                     { 
22                 MessageBoxEx.ShowBox("不允许上传同名文件.", MessageBoxButtons.OK);
23                 bHasBeenTips = true;
24 }
25                 return;
26             }
27             else
28             {
29                     ..................................
30              }
31 }