c1.BgColor = "#009900";

------解决方案--------------------

       HtmlTable ht = new HtmlTable();
       HtmlTableCell tc = new HtmlTableCell();
       HtmlTableRow tr = new HtmlTableRow();
       tc.InnerHtml = "TableCell";
        tc.Style.Add("bgcolor", "#009900");
        tc.Style.Add("background-image", "images/a.gif");       
       tr.Controls.Add(tc);
       ht.Rows.Add(tr);
       ph.Controls.Add(ht);

------解决方案--------------------
背景图还是色？？？

C# code
HtmlTable ht = new HtmlTable();
        HtmlTableRow htr = new HtmlTableRow();
        HtmlTableCell htc = new HtmlTableCell();
        htc.Width = "200px";
        htc.Height = "50px";
        htc.InnerText = "alsdjflsdjf";
        htc.BgColor = "#ff0000";
        htr.Cells.Add(htc);
        ht.Rows.Add(htr);
        this.Controls.Add(ht);

------解决方案--------------------

       tc.Style.Add("background-color", "#FF0000");
       tc.Style.Add("background-image", "images/a.gif");  


这样可以的。

------解决方案--------------------
探讨


        HtmlTable ht = new HtmlTable(); 
        HtmlTableCell tc = new HtmlTableCell(); 
        HtmlTableRow tr = new HtmlTableRow(); 
        tc.InnerHtml = "TableCell"; 
        tc.Style.Add("bgcolor", "#009900"); 
        tc.Style.Add("background-image", "images/a.gif");       
        tr.Controls.Add(tc); 
        ht.Rows.Add(tr); 
        ph.Controls.Add(ht);