C# 比较数据表中的值

我试图在一个datatable上比较新值和现有datatable，如果可用，quantity将相加，但如果不可用，它将在datatable中添加一行

if (HttpContext.Current.Session["Cart"] != null)
{
    DataTable shoppingcart = (DataTable)HttpContext.Current.Session["Cart"];
    for (int i = 0; i < shoppingcart.Rows.Count; i++)
    {
        String checktitle = shoppingcart.Rows[i]["Title"].ToString();
            if (title == checktitle)
            {
                //do something
            }
            else
            {

                ShoppingCart.DataSource = cart.cartrow(shoppingcart);
                ShoppingCart.DataBind();
            }
        }

    }

    else
    {
        HttpContext.Current.Session["Cart"] = cart.shoppingCart();
        ShoppingCart.DataSource = cart.shoppingCart();
        ShoppingCart.DataBind();
    }

}  

您运行以下代码：

ShoppingCart.DataSource = cart.cartrow(shoppingcart);
ShoppingCart.DataBind();

每次您的条件为false时：title==checktitle

我不确定这是不是错误，但您应该构建一些不同的东西，比如：

if (HttpContext.Current.Session["Cart"] != null)
{
    DataTable shoppingcart = (DataTable)HttpContext.Current.Session["Cart"];
    //put here each row you need to bind
    DataTable toBind = new DataTable();  //do more to init the columns, rows, etc

    for (int i = 0; i < shoppingcart.Rows.Count; i++)
    {
        String checktitle = shoppingcart.Rows[i]["Title"].ToString();
            if (title == checktitle)
            {
                //do something
            }
            else
            {
                toBind.add(cart.cartrow(shoppingcart));  //the sintax here is incorect, I code directly here
                //ShoppingCart.DataSource = cart.cartrow(shoppingcart);
                //ShoppingCart.DataBind();
            }
        }
        //bind outside the for cicle
        ShoppingCart.DataSource = toBind ;
        ShoppingCart.DataBind();
    }

    else
    {
        HttpContext.Current.Session["Cart"] = cart.shoppingCart();
        ShoppingCart.DataSource = cart.shoppingCart();
        ShoppingCart.DataBind();
    }

}  

---

我希望这能为您更正代码提供指导。我将其直接编码到浏览器中，不记得初始化数据表或向其中添加行的确切语法

也许您可以使用foreach：

if (HttpContext.Current.Session["Cart"] != null)
{
    DataTable shoppingcart = (DataTable)HttpContext.Current.Session["Cart"];

    foreach (DataRow row in shoppingcart.Rows)
    {
            String checktitle = row["Title"].ToString();
            int price = row["price"].ToString();
            int quantity = row["quantity"].ToString();

            if (title == checktitle)
            {
                //do something
            }
            else
            {

                Session["Cart"] = cart.cartrow(shoppingcart,checktitle,price,quantity);
                ShoppingCart.DataSource = Session["Cart"]  as DataTable();
                ShoppingCart.DataBind();
            }
     }

 }

你的马车

public DataTable cartrow(DataTable _cart,string title,int price,int quantity)
{

    tableRow = _cart.NewRow();
    tableRow["Title"] = title;
    tableRow["Price"] = price;
    tableRow["quantity"] = quantity;
    _cart.Rows.Add(tableRow);
    return _cart;

}

---

您的代码没有显示您的要求。您在哪里比较该值、添加数量并创建新行？对不起，我是编程新手。我创建了一个类来运行我的行添加，修改了tableCollection；枚举操作可能无法执行。

public DataTable cartrow(DataTable _cart,string title,int price,int quantity)
{

    tableRow = _cart.NewRow();
    tableRow["Title"] = title;
    tableRow["Price"] = price;
    tableRow["quantity"] = quantity;
    _cart.Rows.Add(tableRow);
    return _cart;

}