小问题

private void Submit1_ServerClick(object sender, System.EventArgs e)
{
string str="select * from Book";
SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationSettings.AppSettings["ConnectionString"]);

if(TextBox1.Text != null)
{
str=str+" where bookname like '%"+TextBox1.Text+"%'";
}

SqlCommand comm = new SqlCommand(str,conn);

SqlDataAdapter da = new SqlDataAdapter(comm);

DataSet ds = new DataSet();

Label1.Text = DataGrid1.PageCount.ToString();

da.Fill(ds ,"Book");

DataGrid1.DataSource =ds;

DataGrid1.DataBind();

}

private void DataGrid1_PageIndexChanged(object source, System.Web.UI.WebControls.DataGridPageChangedEventArgs e)
{
DataGrid1.CurrentPageIndex = e.NewPageIndex ;

DataGrid1.DataBind();

}

private void TextBox1_TextChanged(object sender, System.EventArgs e)
{
DataGrid1.CurrentPageIndex=0;

}

private void DataGrid1_SelectedIndexChanged(object sender, System.EventArgs e)
{

}
为什么在多次查询后，点下一页时出现ＣＵＲＥＮＴＰＡＧＥＩＮＤＥＸ必须大于０小于ＰＡＧＥＣＯＵＴ的错误