执行需要打开连接的读取器
本文关键字:读取 连接 执行 | 更新日期: 2023-09-27 18:03:13
你好,我一直在为一个项目创建一个订单表单,并且很难将日期编号放到数据行上。我有下面的代码,但得到错误'ExecuteReader需要一个开放的和可用的连接。连接的当前状态是关闭的。如有任何帮助,我将不胜感激。
private void cmbSelectDay_SelectedIndexChanged(object sender, EventArgs e)
{
//variable for case statement
int day = 0;
string Sql = "Select deliveryDayNo from standardOrderDetails order by deliveryDayNo";
SqlConnection conn = new SqlConnection(connStr); // ...
SqlCommand cmd = new SqlCommand(Sql, conn); //there is an error happening here that im not too sure about that would need to be fixed first. but once its fixed this should all work.
SqlDataReader DR = cmd.ExecuteReader();
while (DR.Read())
{
cmbSelectDay.Items.Add(DR[0]);
}
//case statement to take the selected value of the combo box and assign a new value to the variable "day" acordingly.
switch(cmbSelectDay.SelectedText.ToString())
{
case "Monday":
{
day = 1;
break;
}
case "Tuesday":
{
day = 2;
break;
}
case "Wednesday":
{
day = 3;
break;
}
case "Thursday":
{
day = 4;
break;
}
case "Friday":
{
day = 5;
break;
}
case "Saturday":
{
day = 6;
break;
}
}
// DataRow dr = dsLeprechaun.Tables["standardOrderDetails"].Rows.Find(day);
DataRow dr = dsLeprechaun.Tables["standardOrderDetails"].Rows.Find(day.ToString());
dgvOrder.Rows.Add(dr["deliveryDayNo"].ToString());
lblSelectCategory.Visible = true;
lstBoxSelectCategory.Visible = true;
}
所以…打开连接:
using(SqlConnection conn = new SqlConnection(connStr))
using(SqlCommand cmd = new SqlCommand(Sql, conn))
{
conn.Open();
using(SqlDataReader DR = cmd.ExecuteReader())
{
// consume data
}
}
您可能还想查看有助于ADO的工具。NET,例如"dapper"—例如,如果我假设此数据是字符串,我们可以将所有这些缩短为:
using(SqlConnection conn = new SqlConnection(connStr))
{
var days = conn.Query<string>(
"Select deliveryDayNo from standardOrderDetails order by deliveryDayNo"
).ToList();
// now add the items from "days"
}
您需要在调用ExecuteReader()
方法之前打开连接对象conn
试试这个:
SqlConnection conn = new SqlConnection(connStr);
SqlCommand cmd = new SqlCommand(Sql, conn);
conn.Open(); //Add this statement
SqlDataReader DR = cmd.ExecuteReader();
你必须打开连接
conn.Open();
using(SqlDataReader reader = cmd.ExecuteReader())
{
while(reader.Read())
{
//code here
}
}