string[] fs=Directory.GetFiles("你的路径", "*.jpg");
foreach(string s in fs)
{
 //把文件名称加到DataTable中
}

------解决方案--------------------
文件夹就是一颗树.
用遍历树的算法就行了.

------解决方案--------------------

遍历JPG

  private void button1_Click(object sender, EventArgs e)
       {
           try
           {
               if (textBox1.Text.Trim() == "")
               {
                   MessageBox.Show("请输入JPG路径");
                   return;
               }

               string srcPath = "D:\\Microsoft SQL Server\\DataBase";
                     srcPath=textBox1.Text.Trim();
               string[] fileList = System.IO.Directory.GetFileSystemEntries(srcPath);

               foreach (string file in fileList)
               {

                   if (file.Trim().Substring(file.Trim().Length - 3, 3).Trim().ToUpper()=="JPG")
                   {
                       bin.AddNew();
                       cdgv.CurrentRow.Cells["sDish_c"].Value = file.Trim();
                   }
                   //if (file.EndsWith("jpg"))
                   //{
                   //    bin.AddNew();
                   //    cdgv.CurrentRow.Cells["sDish_c"].Value = file.Trim();
                   //}
                   //if (file.EndsWith("JPG"))
                   //{
                   //    bin.AddNew();
                   //    cdgv.CurrentRow.Cells["sDish_c"].Value = file.Trim();
                   //}
                 
               }

           }
           catch (Exception ex)
           {
               MessageBox.Show(ex.ToString());
           }
       }

------解决方案--------------------
同意一楼的