路径显示不下时，中间显示省略号

//路径显示不下时，中间显示省略号
        class CShowShortPath
        {
            public CShowShortPath(string str)
            {
                //统一成反斜杠
                str = str.Replace('/', '\\');
                //收集反斜杆的位置
                List<int> indexs = new List<int>();
                for (int i = 0; i < str.Length; i++)
                {
                    if ('\\' == str[i])
                    {
                        indexs.Add(i);
                    }
                }
                //收集可能的显示形式
                m_strCanShows.Add(str);
                for (int j = indexs.Count / 2, i = j - 1; ; )
                {
                    m_strCanShows.Add(GetShortShow(ref str, ref indexs, i, j));
                    if ((!ValidIndex(indexs,i)) && (!ValidIndex(indexs,j)) )
                    {
                        break;
                    }
                    if ((indexs.Count - 1 - j) > (i - 0))
                    {
                        j++;
                    }
                    else
                    {
                        i--;
                    }
                }
            }
            public List<string> m_strCanShows = new List<string>();
            private string GetShortShow(ref string str, ref List<int> indexs, int indexLeft, int indexRight)
            {
                string str1 = "", str2 = "";
                if (ValidIndex(indexs,indexLeft))
                {
                    str1 = str.Substring(0, indexs[indexLeft]);
                }
                if (ValidIndex(indexs,indexRight))
                {
                    str2 = str.Substring(indexs[indexRight] + 1, str.Length - indexs[indexRight] - 1);
                }
                return str1 + "..." + str2;
            }
            private bool ValidIndex( List<int> indexs, int index)
            {
                return ( index >= 0 ) && ( index < indexs.Count ) ;
            }
        };

public class CShow
        {
            public static void ShowSinglePathIfNoSpace(string strPath, TextBox txtBox)
            {
                ImeBase.CShowShortPath show = new ImeBase.CShowShortPath(strPath);
                for (int i = 0; i < show.m_strCanShows.Count; i++)
                {
                    int iNeedWidth = TextRenderer.MeasureText(show.m_strCanShows[i], txtBox.Font).Width;
                    if (txtBox.Width > iNeedWidth)
                    {
                        txtBox.Text = show.m_strCanShows[i];
                        break;
                    }
                }
            }
        }