Question

我很难将我的计数代码显示在我的标签文字中。这是我的代码，请告诉我如何解决这个问题。

ordering_and_billing.dBase dBase = new ordering_and_billing.dBase();
var mydbconnection = new dBase.dbconnection();

string sql = "SELECT * FROM `order` WHERE eventdate='" + lbldte.Text + "'";

MySqlCommand cmd = new MySqlCommand(sql, mydbconnection.Connection);
mydbconnection.Connection.Open();
MySqlDataReader rdr = cmd.ExecuteReader();
if (rdr.HasRows)
{
    while (rdr.Read())
    {
        Int32 count = (Int32)cmd.ExecuteScalar();
        string disp = count.ToString();
        lblcount.Text = disp;
    }
}

Answer 1

只需使用count功能：

string sql = "SELECT COUNT(*) FROM `order` WHERE eventdate='" + lbldte.Text + "'";

也不要使用ExecuteReader，如果您想要一个像计数值这样的值，请使用ExecuteScalar函数：

lblcount.Text =cmd.ExecuteScalar().toString();

Answer 2

如果你想要的只是记录数，你应该使用SELECT COUNT(*)。

string sql = "SELECT COUNT(*) FROM `order` WHERE eventdate='" + lbldte.Text + "'";

但是，请记住rdr.Read()从sql查询中读取新行。每次时间你得到一个新行，你试图重新运行sql命令（我猜是崩溃），然后分配count标签。因此，您尝试分配count标签计数次。请改用此构造：

int count = 0;
while (rdr.Read())
{
    count++;
}
lblcount.Text = count.ToString(); //only assigns to the Text property once

Answer 3

不管怎样，我现在得到了答案。

ordering_and_billing.dBase dBase = new ordering_and_billing.dBase();
var mydbconnection = new dBase.dbconnection();

string sql = "SELECT * FROM `order` WHERE eventdate='" + lbldte.Text + "'";

MySqlCommand cmd = new MySqlCommand(sql, mydbconnection.Connection);
mydbconnection.Connection.Open();
MySqlDataReader rdr = cmd.ExecuteReader();
int count = 0;
while (rdr.Read())
{
    count ++;
}
lblcount.Text = count.ToString();

如何在标签文字中显示计数？

3 个答案: