string sql = "select *  from xianjinliuliangbiao ";
public void Data(string sql)
    {
        OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("~/DB_Data/caiwu.mdb"));
        DataSet ds = new DataSet();
        OleDbDataAdapter dadt = new OleDbDataAdapter(sql, conn);
        dadt.Fill(ds);
        this.GridView1.DataSource = ds;
        GridView1.DataBind();
    }
    public void Data1(string sql)
    {
        OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("~/DB_Data/caiwu.mdb"));
        DataSet ds = new DataSet();
        OleDbDataAdapter dadt = new OleDbDataAdapter(sql, conn);
        dadt.Fill(ds);
    }
 protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
    {
        this.GridView1.EditIndex = -1;
        Data(sql);
    }
protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        string id = GridView1.DataKeys[e.RowIndex].Values[0].ToString();
        string nf = ((TextBox)(GridView1.Rows[e.RowIndex].Cells[1].Controls[0])).Text.ToString().Trim();
        string jyhd = ((TextBox)(GridView1.Rows[e.RowIndex].Cells[2].Controls[0])).Text.ToString().Trim();
        string tzhd = ((TextBox)(GridView1.Rows[e.RowIndex].Cells[3].Controls[0])).Text.ToString().Trim();
        string czhd = ((TextBox)(GridView1.Rows[e.RowIndex].Cells[4].Controls[0])).Text.ToString().Trim();
        string hlbd = ((TextBox)(GridView1.Rows[e.RowIndex].Cells[5].Controls[0])).Text.ToString().Trim();
        string xjzje = ((TextBox)(GridView1.Rows[e.RowIndex].Cells[6].Controls[0])).Text.ToString().Trim();
        string qmye = ((TextBox)(GridView1.Rows[e.RowIndex].Cells[7].Controls[0])).Text.ToString().Trim();        
        string Sql = "update xianjinliuliangbiao set 年份='" + nf + "',经营活动产生的资金流量='" + jyhd+ "',投资活动产生的资金流量='" + tzhd + "',筹资活动产生的资金流量='" + czhd + "',汇率变动对现金及现金等价物的影响='" +hlbd + "',现金及现金等价物净增加额='" + xjzje + "',期末现金及现金等价物余额='" + qmye + "'";
        Data1(Sql);
        Data(sql);
    }

错误提示是：无法将类型为“System.Web.UI.LiteralControl”的对象强制转换为类型“System.Web.UI.WebControls.TextBox”。

应该有一个编辑框不是？   在GridView中读取一行数据， 读到编辑框中，然后进行修改 就可以了

如果是直接编辑的话，上网查资料吧