更新数据库中的值

Question

我有一个名为 Product 的数据库 table。里面有 ID、ProductName、Brand、Description、Price、Cost 和 Count。我想使用文本框更新计数值。

比如我在文本框里输入一个值，Count下面已经有10了，更新后的值应该是文本框里的值+10。

这是我的代码：

protected void btnAdd_Click(object sender, EventArgs e)
    {
        string productName = ddlName.Text;
        string quantity = tbQuantity.Text;

        string strConnectionString = ConfigurationManager.ConnectionStrings["TrimberlandConnectionString"].ConnectionString;
        SqlConnection myConnect = new SqlConnection(strConnectionString);
        string strCommandText = "Select ProductName FROM Product WHERE ProductName = @ProductName";
        SqlCommand cmd = new SqlCommand(strCommandText, myConnect);
        cmd.Parameters.AddWithValue("@ProductName", productName);
        myConnect.Open();
        SqlDataReader reader = cmd.ExecuteReader();

        addStocks(productName, quantity);

        reader.Close();
        myConnect.Close();
    }

    private void addStocks(string productName, string quantity)
    {
        string strConnectionString = ConfigurationManager.ConnectionStrings["TrimberlandConnectionString"].ConnectionString;
        SqlConnection myConnect = new SqlConnection(strConnectionString);
        string strCommandText = "UPDATE Product SET Count = Count + 1 ";

        SqlCommand cmd = new SqlCommand(strCommandText, myConnect);
        cmd.Parameters.AddWithValue("@ProductName", productName);
        cmd.Parameters.AddWithValue("@Count", quantity);

        myConnect.Open();

        int result = cmd.ExecuteNonQuery();

        if (result > 0)
        {
            MessageBox.Show("Stocks have successfully been added.");
        }

        myConnect.Close();
    }

Answer 1

我想你想修改命令文本：

    string strCommandText = "UPDATE Product SET Count = Count + 1 ";

至

    string strCommandText = "UPDATE Product SET Count = Count + @count WHERE ProductName = @ProductName  ";

从纯功能的角度来看应该就这些了。

但为了使其更加防弹，您应该检查 'quantity' 字符串以确保它确实是一个数字。

Answer 2

您的代码应该是：

protected void btnAdd_Click(object sender, EventArgs e)
{
    string productName = ddlName.Text;
    string quantity = tbQuantity.Text;
    string product_id = "";

    string strConnectionString = ConfigurationManager.ConnectionStrings["TrimberlandConnectionString"].ConnectionString;
    SqlConnection myConnect = new SqlConnection(strConnectionString);
    string strCommandText = "Select ID FROM Product WHERE lower(ProductName) = lower(@ProductName)";
    SqlCommand cmd = new SqlCommand(strCommandText, myConnect);
    cmd.Parameters.AddWithValue("@ProductName", productName);
    myConnect.Open();
    product_id = cmd.ExecuteScalar() == null ? "" : cmd.ExecuteScalar().ToString();
    myConnect.Close();
    if (!String.IsNullOrEmpty(product_id))
        addStocks(product_id, quantity);
}

private void addStocks(string productID, string quantity)
{
    string strConnectionString = ConfigurationManager.ConnectionStrings["TrimberlandConnectionString"].ConnectionString;
    SqlConnection myConnect = new SqlConnection(strConnectionString);
    string strCommandText = "UPDATE Product SET Count = Count + @val where ID = @PID ";

    SqlCommand cmd = new SqlCommand(strCommandText, myConnect);
    cmd.Parameters.AddWithValue("@PID", productID);
    cmd.Parameters.AddWithValue("@val", quantity);
    try{
        myConnect.Open();
        cmd.ExecuteNonQuery();
        MessageBox.Show("Stocks have successfully been added.");
    }
    catch(Exception ex){
        //work with exception
    }
    finally{
        myConnect.Close();
    }
}

更新数据库中的值

Updating Value In Database

c#

asp.net

sql-server

database

shopping-cart