c# - 获取查询的 int 值

Question

我有以下代码。

string connStr = String.Format("server=localhost;user id=root; password=1234;" + "database=Printermangement; pooling=false", "localhost", "root", "1234");
string Query = "select sum(Page_Printed) from printjobdetails where User_ID = 'MyProperty'GROUP by User_ID";
MySqlConnection conDataBase = new MySqlConnection(connStr);
MySqlCommand cmdDataBase = new MySqlCommand(Query, conDataBase);

MessageBox.Show(Query);

我想从此查询中获取 sum，但我不知道如何获取要在消息框中显示的 int 值。我怎样才能做到这一点？

Answer 1

您可以使用 ExecuteScalar方法:

// Prepare the command
string connStr = ...
string Query = "select sum(Page_Printed) from printjobdetails where User_ID = 'MyProperty' GROUP by User_ID";
using(MySqlConnection conDataBase = new MySqlConnection(connStr))
using(MySqlCommand cmdDataBase = new MySqlCommand(Query, conDataBase))
{
    // Execute the command and get the result
    var sum = (int)cmdDataBase.ExecuteScalar();

    // Display the result
    MessageBox.Show(string.Format("Sum: {0}", sum));
}

我还在 using 中放置了您的命令和连接对象 block 。这将确保它们安全关闭，并且它们使用的任何非托管资源都将得到妥善处理。