怎样去判断 一个 DataTable 中是否已经含有指定的记录。

Question

这个不算太好，写个方法作try catch 判断返回值

Answer 1

int i=0;
        for (i=0;i<dtb.Rows.Count;i++)
        {            if (dtb.Rows(i)("userId")==userId)  //此行出错!
            {
                Response.Write("已经存在");
            }
            else
            {
                Response.Write("bu存在");
            }
        }
错误 1 “System.Data.DataTable.Rows”是“属性”，但此处被当做“方法”来使用

Answer 2

我觉得用try catch不好。
用正则表达式应该会快些的

Answer 3

我刚学.net .能帮我把 你们认为比较好的解决方法和代码一起发给我。谢谢！

Answer 4

for (i=0;i<dtb.Rows.Count;i++)
{if (dtb.Rows[i]["userId"]==userId) //此行出错!
{
Response.Write("已经存在");
}
else
{
Response.Write("bu存在");
}
}

Answer 5

Convert.toint32(dtb.rows[i]["userID"])==userID

Answer 6

有一个简单的方法DataRows[] drs = dtb.Select("userID="+userId);
if(drs.Length >0)
{
   //有此 userId
}

Answer 7

for (i=0;i<dtb.Rows.Count;i++)
{if (dtb.Rows[i]["userId"]==userId+"") //此行出错!
{
Response.Write("已经存在");
}
else
{
Response.Write("bu存在");
}
}
加了个+"" 就不用toint转换了。

Answer 8

dtb.Rows[i]["userId"]这是object类型的。。

Answer 9

DataRows[] drs = dtb.Select("userID="+userId.ToString());//忘记看类型了
//DataRows[] drs = dtb.Select("userID="+userId.ToString()+" and (userSex ='"+userSex +"'" +" or userName='"+userName+"')");//举一反三
if(drs.Length >0)
{
   //有此 userId
}

Answer 10

谢谢大家，现在我做了个数量，让程序可在回发（模拟对已存在货品购物时）时加1  ,可两个控件都总是显示数量是1 ,怎么也不加。大家再帮我是什么原因？protected void Page_Load(object sender, EventArgs e)
    {
       
        if (IsPostBack)
        {
            int userId = Convert.ToInt32(this.DetailsView1.Rows[0].Cells[1].Text);
            string userName = this.DetailsView1.Rows[1].Cells[1].Text.ToString();
            string userSex = this.DetailsView1.Rows[4].Cells[1].Text.ToString();
                       //DataSet ds = new DataSet();
            DataTable dtb = new DataTable("MyCar");
            dtb.Columns.Add("userId", typeof(int));
            dtb.Columns.Add("userName");
            dtb.Columns.Add("userSex");
            dtb.Columns.Add("TheCount");            int a = 1;
            DataRow dRow = dtb.NewRow();
            dRow["userId"] = userId;
            dRow["userName"] = userName;
            dRow["userSex"] = userSex;
            dRow["TheCount"] = a;
            DataRow[] drs = dtb.Select("userID=" + userId);
            if (drs.Length > 0)
            {
                a+=1;
            }
            else
            {
                a = 1;
            }            dtb.Rows.Add(dRow);            Session["myCar"] = dtb;            this.DetailsView2.DataSource = (DataTable)Session["myCar"];
            this.DetailsView2.DataBind();            this.Gv2.DataSource = dtb.DefaultView;
            this.Gv2.DataBind();        }

Answer 11

protected void Page_Load(object sender, EventArgs e)
    {
        DataTable dtb = Session["myCar"] as DataTable;
        if(dtb==null)
{        
            //DataSet ds = new DataSet();
            DataTable dtb = new DataTable("MyCar");
            dtb.Columns.Add("userId", typeof(int));
            dtb.Columns.Add("userName");
            dtb.Columns.Add("userSex");
            dtb.Columns.Add("TheCount");
}
        if (IsPostBack)
        {
            int userId = Convert.ToInt32(this.DetailsView1.Rows[0].Cells[1].Text);
            string userName = this.DetailsView1.Rows[1].Cells[1].Text.ToString();
            string userSex = this.DetailsView1.Rows[4].Cells[1].Text.ToString();
           
            int a = 1;
            DataRow dRow = dtb.NewRow();
            dRow["userId"] = userId;
            dRow["userName"] = userName;
            dRow["userSex"] = userSex;
            //dRow["TheCount"] = a;            DataRow[] drs = dtb.Select("userID=" + userId);
            if (drs.Length > 0)
            {
                a+=1;
            }
            else
            {
                a = 1;
            }
            dRow["TheCount"] = a; //在这赋值
            dtb.Rows.Add(dRow);            Session["myCar"] = dtb;            this.DetailsView2.DataSource = (DataTable)Session["myCar"];
            this.DetailsView2.DataBind();            this.Gv2.DataSource = dtb.DefaultView;
            this.Gv2.DataBind();        }

Answer 12

dataview dv=datatable.default;
dv.Rowfile = "想要过滤信息";

Answer 13

可能我的这段代码还有逻辑问问题,请大家再帮我看看. protected void BtnAddToCar_Click(object sender, EventArgs e)
    {        int goodsId = Int32.Parse(this.DetailsView1.Rows[0].Cells[1].Text);
        string theGoodsName = (this.DetailsView1.Rows[1].Cells[1].Text).ToString();
        decimal thePrice = Convert.ToDecimal(this.DetailsView1.Rows[5].Cells[1].Text);        //DataTable dtb = Session["myCar"] as DataTable;
        // DataTable dtb = new DataTable("MyCar");
               if (Session["myCar"] == null)
        {
            //DataSet ds = new DataSet();
            DataTable dtb = new DataTable("MyCar");
            dtb.Columns.Add("goodsId", typeof(int));
            dtb.Columns.Add("thtGoodsName");
            dtb.Columns.Add("thtPrice");
            dtb.Columns.Add("TheCount");            DataRow dRow = dtb.NewRow();
            dRow["goodsId"] = goodsId;
            dRow["thtGoodsName"] = theGoodsName;
            dRow["thtPrice"] = thePrice;
            dRow["TheCount"] = 1;
            dtb.Rows.Add(dRow);            Session["myCar"] = dtb;
        }        else
        {
            DataTable dtb = Session["myCar"] as DataTable;
            //dtb.Columns.Add("goodsId", typeof(int));
            int a = 1;
            DataRow[] drs = dtb.Select("goodsId=" + goodsId);
            if (drs.Length > 0)
            {
                a += 1;
                //怎样将 a 的值写入 DataTable dtb 而不需要添加新行！
                //DataRow[] drs = dtb.Rows[goodsId];
            }            else
            {
                a = 1;
                DataRow dRow = dtb.NewRow();
                dRow["goodsId"] = goodsId;
                dRow["thtGoodsName"] = theGoodsName;
                dRow["thtPrice"] = thePrice;
                dRow["TheCount"] = a;
                dtb.Rows.Add(dRow);
            }            Session["myCar"] = dtb;
              this.DetailsView2.DataSource = dtb;
            this.DetailsView2.DataBind();
        }
  }

Answer 14

            if (drs.Length > 0)
            {
                a += 1;
                //怎样将 a 的值写入 DataTable dtb 而不需要添加新行！
                drs[0]["TheCount"] = a;
            }

Answer 15

if(dt.rows.count>0)
{}
else
{}