如何从datalist更新数据库表?
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我正在建立一个电子商务网站,我使用数据列表显示我的产品,当我按下“添加到购物车”按钮时,它们应该被添加到数据库表中但由于某种原因,产品不是在数据库表中更新。此外,单击第一个产品会出现错误,说“已经有一个打开的阅读器”,显示错误的行是“int result = comm.ExecuteNonQuery();”
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Globalization;
namespace MWM1812
{
public partial class productCatalog : System.Web.UI.Page
{
public enum MessageType { Success, Error, Info, Warning };
protected void ShowMessage(string Message, MessageType type)
{
ScriptManager.RegisterStartupScript(this, this.GetType(), System.Guid.NewGuid().ToString(), "ShowMessage('" + Message + "','" + type + "');", true);
}
protected void Page_Load(object sender, EventArgs e)
{
}
protected void DataList1_SelectedIndexChanged(object sender, EventArgs e)
{
}
protected void DataList1_ItemCommand(object source, DataListCommandEventArgs e)
{
if (e.CommandName == "AddToCart")
{
Session["uid"] = 1;
Label lbl = (Label)e.Item.FindControl("PIDLabel");
lblAtC.Text = lbl.Text;
ShowMessage("Product successfully added to Cart", MessageType.Success);
string connStr = ConfigurationManager.ConnectionStrings["MWM1812ConnString"].ConnectionString;
SqlConnection conn = new SqlConnection(connStr);
conn.Open();
string sqlQuery = "SELECT * FROM tblShoppingCart WHERE uid=@uid AND pid=@pid";
SqlCommand comm = new SqlCommand(sqlQuery, conn);
comm.Parameters.AddWithValue("@uid", Session["uid"]);
comm.Parameters.AddWithValue("@pid", lblAtC.Text.Trim());
using (SqlDataReader reader = comm.ExecuteReader())
{
if (reader.HasRows)
{
string sqlQuery2 = "UPDATE tblShoppingCart SET qty=qty+1 WHERE uid=@uid AND pid=@pid";
SqlCommand comm1 = new SqlCommand(sqlQuery2, conn);
comm1.Parameters.AddWithValue("@qty", 1);
comm1.Parameters.AddWithValue("@dtShopped", DateTime.Now.ToString());
//// Add code for adding parameters and executing sqlQuery2
int result = comm1.ExecuteNonQuery();
}
else
{
string sqlQuery1 = "INSERT INTO tblShoppingCart (uid, pid, qty, dtShopped) VALUES (@uid, @pid, @qty, @dtShopped)";
SqlCommand comma = new SqlCommand(sqlQuery1, conn);
comma.Parameters.AddWithValue("@uid", Session["uid"]);
comma.Parameters.AddWithValue("@pid", lblAtC.Text);
comma.Parameters.AddWithValue("@qty", 1);
//comm.Parameters.AddWithValue("@dtShopped", DateTime.Now.ToLongDateString());
comma.Parameters.AddWithValue("@dtShopped", DateTime.Now.ToString());
int result = comma.ExecuteNonQuery();
}
}
}
}
}
}
答案
尝试像这样更新代码:
if (e.CommandName == "AddToCart") {
bool productExists = false;
Session["uid"] = 1;
Label lbl = (Label) e.Item.FindControl("PIDLabel");
lblAtC.Text = lbl.Text;
ShowMessage("Product successfully added to Cart", MessageType.Success);
string connStr = ConfigurationManager.ConnectionStrings["MWM1812ConnString"].ConnectionString;
SqlConnection conn = new SqlConnection(connStr);
conn.Open();
string sqlQuery = "SELECT * FROM tblShoppingCart WHERE uid=@uid AND pid=@pid";
SqlCommand comm = new SqlCommand(sqlQuery, conn);
comm.Parameters.AddWithValue("@uid", Session["uid"]);
comm.Parameters.AddWithValue("@pid", lblAtC.Text.Trim());
using(SqlDataReader reader = comm.ExecuteReader()) {
productExists = reader.HasRows;
}
if (productExists) {
string sqlQuery2 = "UPDATE tblShoppingCart SET qty=qty+1 WHERE uid=@uid AND pid=@pid";
// Add code for adding parameters and executing sqlQuery2
} else {
string sqlQuery1 = "INSERT INTO tblShoppingCart (uid, pid, qty, dtShopped) VALUES (@uid, @pid, @qty, @dtShopped)";
SqlCommand comma = new SqlCommand(sqlQuery, conn);
comma.Parameters.AddWithValue("@uid", Session["uid"]);
comma.Parameters.AddWithValue("@pid", lblAtC.Text);
comma.Parameters.AddWithValue("@qty", 1);
//comm.Parameters.AddWithValue("@dtShopped", DateTime.Now.ToLongDateString());
comma.Parameters.AddWithValue("@dtShopped", DateTime.Now.ToString());
int result = comma.ExecuteNonQuery();
}
}
请注意使用reader.HasRows属性来确定产品是否已存在。此外,SqlDataReader包含在using
块中以便将其处理掉。
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