c# - DropdownList 选择要标记的值

Question

我不断获取名称而不是价格。我想要的是在 DropdownList 上选择一个值并将其价格加载到标签上。

private void GetData()
{
    SqlConnection connection = new SqlConnection("Data Source = localhost\\SQLEXPRESS;Initial Catalog = MejOnlineManagementDB00;Integrated Security=True;");
    connection.Open();
    SqlCommand sqlCmd = new SqlCommand(@"SELECT price
                                            FROM Products3
                                            WHERE productName='" + DropDownList1.SelectedItem.Value.ToString() + "'", connection);
    SqlDataReader rdr = sqlCmd.ExecuteReader();
    while (rdr.Read())
    {
        lblPrice.Text = DropDownList1.SelectedValue.ToString();
    }
    connection.Close();
}

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
    lblPrice.Text=DropDownList1.SelectedItem.Value.ToString();
}

上面是我的selectedIndex。

Answer 1

将您的代码更改为:

        private void GetData()
        {
            SqlConnection connection = new SqlConnection("Data Source = localhost\\SQLEXPRESS;Initial Catalog = MejOnlineManagementDB00;Integrated Security=True;");
            connection.Open();
            SqlCommand sqlCmd = new SqlCommand(@"SELECT price
                                                FROM Products3
                                                WHERE productName='" + DropDownList1.SelectedItem.Value.ToString() + "'", connection);
            SqlDataReader rdr = sqlCmd.ExecuteReader();
            if(dr.HasRows)
            {
                while (rdr.Read())
                {
                    lblPrice.Text = rdr.GetValue(0).ToString(); //  if price is  string use GetString(0))
                }
            }
            connection.Close();
        }

编辑:

 protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        GetData(); 
    }