C#编程：用Substring获取文件路径文件名扩展名

private void button1_Click(object sender, EventArgs e)
        {
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text = openFileDialog1.FileName;
                string strAll = openFileDialog1.FileName;
                string strPath = 
                    strAll.Substring(0, strAll.LastIndexOf("\\") + 1);
                string strFileName=
                    strAll.Substring(strAll.LastIndexOf("\\")+1,
                    strAll.LastIndexOf(".")-
                    (strAll.LastIndexOf("\\")+1));
                string strFileext =
                    strAll.Substring(strAll.LastIndexOf(".") + 1,
                    strAll.Length-strAll.LastIndexOf(".")-1
                    );

                label1.Text = "文件路径： " + strPath;
                label2.Text = "文件名称： " + strFileName;
                label3.Text = "扩展名： " + strFileext;
            }
        }

小结：
IndexOf()和LastIndexOf() 如果没找到匹配字符返回-1；