问题出在哪里

通过gridview显示数据，其中最后一列为image1控件，通过判断 e.Row.Cells[8].Text的值来动态显示不同的图片，但是刚打开时页面显示正常，但点击翻页按钮后图片的链接就丢失了，请问问题在哪里？
  protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {   
        Image img = e.Row.FindControl("Image1") as Image;
        if (img != null)
        {
            string val = e.Row.Cells[8].Text;
            if (val.Equals("1"))
            {
                img.ImageUrl = "../jx.jpg";
            }
            else if (val.Equals("2"))
            {
                img.ImageUrl = "../dw.jpg";
            }
            else
            {
                img.Visible = false;
            }        }
    }    public void bind()
    {        string SqlStr = "select  * from dqwh";
        DataSet ds = new DataSet();
        try
        {
            SqlConnection conn = new SqlConnection(strConn);
            if (conn.State.ToString() == "Closed") conn.Open();
            SqlDataAdapter da = new SqlDataAdapter(SqlStr, conn);
            da.Fill(ds, "dqwh");
            if (conn.State.ToString() == "Open") conn.Close();
            GridView1.DataSource = ds.Tables[0].DefaultView;
            GridView1.DataBind();            btnFirst.Enabled = true;
            btnPrev.Enabled = true;
            btnNext.Enabled = true;
            btnLast.Enabled = true;            LblCurrentIndex.Text = "第 " + (GridView1.PageIndex + 1).ToString() + " 页";
            LblPageCount.Text = "共 " + GridView1.PageCount.ToString() + " 页";
            LblRecordCount.Text = "总共 " + ds.Tables[0].Rows.Count.ToString() + " 条";
            if (GridView1.PageIndex == 0)
            {
                btnFirst.Enabled = false;
                btnPrev.Enabled = false;
            }
            else if (GridView1.PageIndex == GridView1.PageCount - 1)
            {
                btnNext.Enabled = false;
                btnLast.Enabled = false;
            }
            pageDropDownList.Items.Clear();
            for (int i = 1; i < GridView1.PageCount + 1; i++)
            {
                pageDropDownList.Items.Add(i.ToString());
            }
            pageDropDownList.SelectedValue = Convert.ToString(GridView1.PageIndex + 1);
                        btnFirst.CommandName = "1";
            btnPrev.CommandName = (GridView1.PageIndex == 0 ? "1" : GridView1.PageIndex.ToString());            btnNext.CommandName = (GridView1.PageCount == 1 ? GridView1.PageCount.ToString() : (GridView1.PageIndex + 2).ToString());
            btnLast.CommandName = GridView1.PageCount.ToString();        }
        catch (Exception ex)
        {
            Response.Write("数据库错误，错误原因：" + ex.Message);
            Response.End();
        }
    }
    protected void PagerButtonClick(object sender, EventArgs e)
    {
        GridView1.PageIndex = Convert.ToInt32(((LinkButton)sender).CommandName) - 1;
        bind();
    }
   
    protected void pageDropDownList_SelectedIndexChanged(object sender, EventArgs e)
    {
        GridView1.PageIndex = Convert.ToInt32(pageDropDownList.SelectedValue) - 1;
        bind();
    }