if (ds.Tables[0].Rows.Count != 0) 出错 无法找到表 0。

Question

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;public partial class image_Detail : System.Web.UI.Page
{
    string sqlstr;
    DB db = new DB();
    DataSet ds = new DataSet();
    int PageSize;
    int CurrentPage;
    int RecordCount;
    int PageCount;    protected void Page_Load(object sender, EventArgs e)
    {
        sqlstr = "select * from image";
        //Response.Write(Request.QueryString.Get(0).ToString().Trim());
        //Label3.Text = Request.QueryString.Get(0).ToString().Trim();
        ds = db.GetDataTableBySql(sqlstr);
        if (ds.Tables[0].Rows.Count != 0)
        {
            this.DataList1.DataSource = ds.Tables[0].DefaultView;
            this.DataList1.DataBind();
        }
        ViewState["CurrentPage"] = 0;
        PageSize = 3;
        sqlstr = "select * from image";
        ds = db.GetDataTableBySql(sqlstr);
        if (ds.Tables[0].Rows.Count != 0)
        {
            this.DataList1.DataSource = ds.Tables[0].DefaultView;
            this.DataList1.DataBind();
        }        if (Page.IsPostBack == false)
        {
            ViewState["PageIndex"] = 0;            sqlstr = "select count(*) as count from image";
            ds = db.GetDataTableBySql(sqlstr);
            if (ds.Tables[0].Rows.Count != 0)
            {
                RecordCount = int.Parse(ds.Tables[0].Rows[0]["count"].ToString());
            }
            else
            {
                RecordCount = 0;
            }
            if (RecordCount % PageSize == 0)
            {
                PageCount = RecordCount / PageSize;
            }
            else
            {
                PageCount = RecordCount / PageSize + 1;
            }
            ViewState["PageCount"] = PageCount;
            this.Label2.Text = PageCount.ToString();  //显示总页数
            BindList();        }
    }    private void BindList()
    {
        int StartIndex = CurrentPage * PageSize;  //设定导入的起始地址           
        sqlstr = "select * from image";
        SqlConnection con = new SqlConnection();
        con.ConnectionString = db.GetConnectionString();
        con.Open();
        SqlDataAdapter da = new SqlDataAdapter(sqlstr, con);
        da.Fill(ds, StartIndex, PageSize, "image");        this.DataList1.DataSource = ds.Tables["image"].DefaultView;
        this.DataList1.DataBind();        PageCount = (int)ViewState["PageCount"];//获得总页数
        this.ImageButton1.Enabled = true;
        this.ImageButton2.Enabled = true;
        if (CurrentPage == (PageCount - 1))
            this.ImageButton2.Enabled = false;
        if (CurrentPage == 0)
            this.ImageButton1.Enabled = false;
        this.Label1.Text = Convert.ToString(CurrentPage + 1);
    }    protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
    {
        CurrentPage = (int)ViewState["PageIndex"];//获得当前页索引        CurrentPage = CurrentPage - 1;
        ViewState["PageIndex"] = CurrentPage;
        BindList();
    }
    protected void ImageButton2_Click(object sender, ImageClickEventArgs e)
    {
        CurrentPage = (int)ViewState["PageIndex"];//获得当前页索引        CurrentPage = CurrentPage + 1;
        ViewState["PageIndex"] = CurrentPage;
        BindList();
    }
}

Answer 1

ds = db.GetDataTableBySql(sqlstr);ds是个DataSet，而GetDataTableBySql()方法返回DataTable看看db类中有没有返回DataSet的方法如果没有，直接定义一个DatatTable类型的变量dt
dt = db.GetDataTableBySql(sqlstr);
if (dt.Rows.Count != 0)
{
...
}

Answer 2

在DB类里面定义么！
DB类代码：
  using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;/// <summary>
/// DB 的摘要说明
/// </summary>
public class DB
{
    public SqlConnection Con = new SqlConnection();
    public SqlCommand Com = new SqlCommand();
    public SqlDataAdapter Da = new SqlDataAdapter();
    public DataSet Ds = new DataSet();
    public DB()
    {
        //
        // TODO: 在此处添加构造函数逻辑
        //
    }
    public String GetConnectionString()
    {
        String ConStr;
        ConStr = System.Configuration.ConfigurationManager.AppSettings.Get(0).ToString();
        return ConStr;
        
    }
    public DataSet GetDataTableBySql(String SqlStr)
    {
        Con.ConnectionString = GetConnectionString();
        Com.Connection = Con;
        Com.CommandText = SqlStr;
        Da.SelectCommand = Com;
        try
        {
            Ds.Clear();
            Con.Open();
            Da.Fill(Ds);
            Con.Close();
        }
        catch (SqlException)
        {
            Con.Close();
        }
        return Ds;
    }
    public Boolean UpdateDataBySql(String SqlStr)
    {
        Con.ConnectionString = GetConnectionString();
        Com.Connection = Con;
        Com.CommandText = SqlStr;
        try
        {
            Con.Open();
            Com.ExecuteNonQuery();
            Con.Close();
            return true;
        }
        catch (Exception)
        {
            Con.Close();
            return false;
        }
    }
}

Answer 3

学会看提示，先判断table是否是null
if (ds.Tables.Count==0 || ds.Tables[0].Rows.Count == 0) return;

Answer 4

支持楼上的  ，一般用ds 的时候 
先判断ds为不为空
然后里面的表 为不为空，
最后判断 表里面的行为不为空
最后 才能放心的用这个里面的数据
如果在程序中 不判断的话 ，一般会有bug

Answer 5

“ds = db.GetDataTableBySql(sqlstr);”
调试运行，先看看这个返回值是否正确