Question

大家好

con.Close();
            int buttoncounter= -1;
            {
                SqlCommand cmd = new SqlCommand("select count(*) from buttons", con);
                con.Open();
                buttoncounter = Convert.ToInt32(cmd.ExecuteScalar()) + 1;
                con.Close();
            }

我计算数据库中有多少行

for (int i = 1; i < buttoncounter; i++)
        {

            var buttonmenu = new Button
            {

                HeightRequest = 100,
                WidthRequest = 100,
                Margin = 5,
                CornerRadius = 15,
                BackgroundColor = Color.FromRgb(192, 192, 192),

            };
            con.Close();
            buttonmenu.Clicked += butonmenu;
            buttons.Children.Add(buttonmenu);
            if (con.State.ToString() == "Open")
            {

            }
            else
            {
                con.Open();
            }
            SqlCommand getir = new SqlCommand("select * from butonlar where id = '" + i.ToString() + "'", con);
            SqlDataReader dr = getir.ExecuteReader();
            while (dr.Read())
            {

                buttonmenu.Text = dr.GetValue(0).ToString();
                con.Close();
                break;
            }

我使用这种方法创建按钮，让我们以为buttons中有4个值。如果用户删除第2行，则它将为1,3,4，程序将创建4个按钮，而2将为2。按钮的名称为空，我应该防止创建空按钮

id不是pk

Answer 1

如果要防止在Text为null时创建按钮，则需要在创建按钮之前重新排列逻辑以执行查询

var value = dr.GetValue(0).ToString();

// check is value is empty before creating button
if (!string.IsNullOrEmpty(value)) {
  var buttonmenu = new Button
  ...
}

Answer 2

我解决了这个问题

代码已更新：

SqlCommand getirme = new SqlCommand("select * from butonlar where id = '"+i.ToString()+"'", baglanti);
                SqlDataReader okumasa = getirme.ExecuteReader();
                while (okumasa.Read())
                {
                    value = okumasa.GetValue(2).ToString();
                    break;

                }
                // check is value is empty before creating button
                if (value == i.ToString())
                {
                    var buttonmenu = new Button
                    {

if (value == i.ToString())之前，已设置为检测哪个记录为空，但是现在，它会比较id和i 和如果与匹配” ，则会创建按钮。

根据ID创建按钮

2 个答案: