Question

UPDATE Ware
SET Price = Price * 1.02
WHERE WareNr > 0 AND WareNr <= 20000 AND Price >= 200

此代码在我的SQL服务器中运行良好。

现在我必须把它放到一个c＃程序中，我不太清楚如何做到这一点。我对此非常陌生（获得了一些基本代码来进行更新），但我不确定如何做到这一点。

如果有人可以举例说明如何将其实现为“更新商品”按钮，我将非常感激

Answer 1

有几种方法可以做到这一点。您可以使用SqlConnection和SqlCommand类;

using (SqlConnection connection = new SqlConnection(connectionString))
{
    string queryString = "UPDATE Ware SET Price = Price * 1.02 WHERE WareNr > 0 AND WareNr <= 20000 AND Price >= 200";
    SqlCommand command = new SqlCommand(queryString, connection);
    connection.Open();
    command.ExecuteNonQuery();
    connection.Close();
}

这里采用parameterized queries;

的方式

using (SqlConnection connection = new SqlConnection(connectionString))
{
    string queryString = "UPDATE Ware SET Price = @Price1 WHERE WareNr > @WareNr1 AND WareNr <= @WareNr2 AND Price >= @Price2";
    SqlCommand command = new SqlCommand(queryString, connection);
    command.Parameters.AddWithValue("@Price1", 100 * 1.02);
    command.Parameters.AddWithValue("@WareNr1", 0);      
    command.Parameters.AddWithValue("@WareNr2", 20000);   
    command.Parameters.AddWithValue("@Price2", 200);   
    connection.Open();
    command.ExecuteNonQuery();
    connection.Close();
}

Data Access and Modeling

Answer 2

string query = "UPDATE Ware SET Price = (Price * 1.02) WHERE WareNr > 0 AND WareNr <= 20000 AND Price >= 200";

using(SqlConnection conn = new SqlConnection("YourConnectionString"))
{
    using(SqlCommand comm = new SqlCommand(query, conn))
    {
        conn.Open();
        comm.ExecuteNonQuery();
    }
}

Answer 3

string connectionString = "Server=localhost;Database=dbName;Uid=Username;Pwd=Password";
using (var sqlConnection = new SqlConnection(connectionString))
{
    var query = @"UPDATE Ware
                    SET Price = @Price
                  WHERE WareNr > 0 AND WareNr <= 20000 AND Price >= 200";

    sqlConnection.Open();
    using (var command = new SqlCommand(query, sqlConnection))
    {
        command.Parameters.AddWithValue("@Price", 100 * 1.02);
        var dataReader = command.ExecuteNonQuery();
    }

    sqlConnection.Close();
}

Answer 4

每个人都专注于如何进行更新的问题，但用户要求提供一个如何执行此操作的示例。

“给我举例说明如何将其实现为”更新商品“按钮”

这是我的贡献

的web.config

<configuration>
  <connectionStrings>
    <add name="connectionString" connectionString="Persist Security Info=True;User ID=YOUR_USER_ID;Password=YOUR_PASSWORD;Initial Catalog=YOUR_DATABASE_NAME;data source=LOCALHOST;Pooling=true;Connection Lifetime=60;Max Pool Size=100;" providerName="System.Data.SqlClient"/>
  </connectionStrings>
</configuration>

ASPX

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeFile="Default.aspx.cs" Inherits="_Default" %>

<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
    Price Rate:
    <asp:TextBox ID="txtPriceRate" runat="server" />
    <br />
    New Price:
    <asp:TextBox ID="txtNewPrice" runat="server" />
    <br />
    Limit Price:
    <asp:TextBox ID="txtPriceLimit" runat="server" />
    <br />
    Min WareNr:
    <asp:TextBox ID="txtWareMin" runat="server" />
    <br />
    Max WareNr:
    <asp:TextBox ID="txtWareMax" runat="server" />
    <br />
    <asp:Button ID="btnUpdate" runat="server" Text="Update" OnClick="btnUpdate_Click" />
</asp:Content>

aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void btnUpdate_Click(object sender, EventArgs e)
    {
        // You will need to put some validations before try to convert the values

        try
        {
            decimal priceRate = Convert.ToDecimal(this.txtPriceRate.Text);
            decimal newPrice = Convert.ToDecimal(this.txtNewPrice.Text);
            decimal priceLimit = Convert.ToDecimal(this.txtPriceLimit.Text);
            int wareMin = Convert.ToInt32(this.txtWareMin.Text);
            int wareMax = Convert.ToInt32(this.txtWareMax.Text);

            Update(newPrice * priceRate, priceLimit, wareMin, wareMax);
        }
        catch
        {

        }
    }

    public static void Update(decimal paramPrice, decimal paramPriceLimit, int paramWareMin, int paramWareMax)
    {
        string connectionString = System.Configuration.ConfigurationManager.AppSettings["connectionString"].ToString();

        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            String query = "UPDATE Ware SET Price = @paramPrice WHERE WareNr > @paramWareMin AND WareNr <= @paramWareMax AND Price >= @paramPriceLimit";

            SqlCommand command = new SqlCommand(query, connection);
            command.Parameters.Add("@paramPrice", "paramPrice");
            command.Parameters.Add("@paramPriceLimit", "paramPriceLimit");
            command.Parameters.Add("@paramWareMin", "paramWareMin");
            command.Parameters.Add("@paramWareMax", "paramWareMax");

            connection.Open();
            command.ExecuteNonQuery();
            connection.Close();
        }
    }
}

如何在我的c＃代码中使用此Update语句？

4 个答案: