C# 中已经有一个打开的 Datareader 关联
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【中文标题】C# 中已经有一个打开的 Datareader 关联【英文标题】：There is already an open Datareader associated in C# 【发布时间】：2013-10-18 15:21:55 【问题描述】：我似乎找不到这个错误背后的原因。有人可以查看我的代码吗？
private void button2_Click_1(object sender, EventArgs e)
con.Open();
string check
= "Select block, section, size from interment_location where block='"
+ textBox12.Text
+ "' and section='"
+ textBox13.Text
+ "' and size='"
+ textBox14.Text
+ "'";
SqlCommand cmd1 = new SqlCommand(check, con);
SqlDataReader rdr;
rdr = cmd1.ExecuteReader();
try
if (textBox1.Text == ""
|| textBox2.Text == ""
|| textBox3.Text == ""
|| textBox4.Text == ""
|| textBox7.Text == ""
|| textBox8.Text == ""
|| textBox9.Text == ""
|| textBox10.Text == ""
|| dateTimePicker1.Value.ToString("yyyyMMdd HH:mm:ss") == ""
|| dateTimePicker2.Value.ToString("yyyyMMdd HH:mm:ss") == ""
|| textBox11.Text == ""
|| dateTimePicker3.Value.ToString("yyyyMMdd HH:mm:ss") == ""
|| textBox12.Text == ""
|| textBox13.Text == ""
|| textBox14.Text == "")
MessageBox.Show(
"Please input a value!",
"Error",
MessageBoxButtons.OK,
MessageBoxIcon.Exclamation);
else if (rdr.HasRows == true)
MessageBox.Show("Interment Location is already reserved.");
textBox12.Clear();
textBox13.Clear();
textBox14.Clear();
textBox12.Focus();
else if (MessageBox.Show(
"Are you sure you want to reserve this record?",
"Reserve",
MessageBoxButtons.YesNo,
MessageBoxIcon.Question) == DialogResult.Yes)
SqlCommand cmd4 = new SqlCommand(
"insert into owner_info(ownerf_name, ownerm_name,"
+ " ownerl_name, home_address, tel_no, office)"
+ " values('"
+ textBox1.Text
+ "', '"
+ textBox2.Text
+ "', '"
+ textBox3.Text
+ "', '"
+ textBox4.Text
+ "', '"
+ textBox7.Text
+ "', '"
+ textBox8.Text
+ "')",
con);
cmd.ExecuteNonQuery();
SqlCommand cmd5 = new SqlCommand(
"insert into deceased_info(deceased_id, name_of_deceased, "
+ "address, do_birth, do_death, place_of_death, "
+ "date_of_interment, COD_id, place_of_vigil_id, "
+ "service_id, owner_id) values('"
+ ownerid
+ "','"
+ textBox9.Text
+ "', '"
+ textBox10.Text
+ "', '"
+ dateTimePicker1.Value.ToString("yyyyMMdd HH:mm:ss")
+ "', '"
+ dateTimePicker2.Value.ToString("yyyyMMdd HH:mm:ss")
+ "', '"
+ textBox11.Text
+ "', '"
+ dateTimePicker3.Value.ToString("yyyyMMdd HH:mm:ss")
+ "', '"
+ ownerid
+ "', '"
+ ownerid
+ "', '"
+ ownerid
+ "', '"
+ ownerid
+ "')",
con);
cmd.ExecuteNonQuery();
SqlCommand cmd6 = new SqlCommand(
"insert into interment_location(lot_no, block, section, "
+ "size, garden_id) values('"
+ ownerid
+ "','"
+ textBox12.Text
+ "', '"
+ textBox13.Text
+ "', '"
+ textBox14.Text
+ "', '"
+ ownerid
+ "')",
con);
cmd.ExecuteNonQuery();
MessageBox.Show(
"Your reservation has been made!",
"Reserve",
MessageBoxButtons.OK,
MessageBoxIcon.Information);
catch (Exception x)
MessageBox.Show(x.Message);
con.Close();
这是我之后编辑的唯一代码。
【问题讨论】：
***.com/questions/2519379/…请参考链接 我已经关闭了该方法。我是不是放错地方了？ 你正在关闭连接而不是阅读器！ 请看下面的答案：***.com/a/4472414/2424 它展示了使用连接、命令、读取器和参数对象的最佳实践方式。就你目前的代码而言，它可能会泄漏内存、sql 连接并允许 sql 注入攻击。 Exception: There is already an open DataReader associated with this Connection which must be closed first的可能重复 【参考方案1】：试试下面的代码，看看是否适合你。
else if (rdr.HasRows == true)
MessageBox.Show("Interment Location is already reserved.");
textBox12.Clear();
textBox13.Clear();
textBox14.Clear();
textBox12.Focus();
rdr.close() // close your reader here!
【讨论】：
【参考方案2】：private void button2_Click_1(object sender, EventArgs e)
con.Open();
string check
= "Select block, section, size from interment_location where block='"
+ textBox12.Text
+ "' and section='"
+ textBox13.Text
+ "' and size='"
+ textBox14.Text
+ "'";
SqlCommand cmd1 = new SqlCommand(check, con);
SqlDataReader rdr;
rdr = cmd1.ExecuteReader();
try
if (textBox1.Text == ""
|| textBox2.Text == ""
|| textBox3.Text == ""
|| textBox4.Text == ""
|| textBox7.Text == ""
|| textBox8.Text == ""
|| textBox9.Text == ""
|| textBox10.Text == ""
|| dateTimePicker1.Value.ToString("yyyyMMdd HH:mm:ss") == ""
|| dateTimePicker2.Value.ToString("yyyyMMdd HH:mm:ss") == ""
|| textBox11.Text == ""
|| dateTimePicker3.Value.ToString("yyyyMMdd HH:mm:ss") == ""
|| textBox12.Text == ""
|| textBox13.Text == ""
|| textBox14.Text == "")
MessageBox.Show(
"Please input a value!",
"Error",
MessageBoxButtons.OK,
MessageBoxIcon.Exclamation);
else if (rdr.HasRows == true)
MessageBox.Show("Interment Location is already reserved.");
textBox12.Clear();
textBox13.Clear();
textBox14.Clear();
textBox12.Focus();
else if (MessageBox.Show(
"Are you sure you want to reserve this record?",
"Reserve",
MessageBoxButtons.YesNo,
MessageBoxIcon.Question) == DialogResult.Yes)
if (!rdr.IsClosed)
rdr.Close(); //close the data reader
SqlCommand cmd4 = new SqlCommand(
"insert into owner_info(ownerf_name, ownerm_name,"
+ " ownerl_name, home_address, tel_no, office)"
+ " values('"
+ textBox1.Text
+ "', '"
+ textBox2.Text
+ "', '"
+ textBox3.Text
+ "', '"
+ textBox4.Text
+ "', '"
+ textBox7.Text
+ "', '"
+ textBox8.Text
+ "')",
con);
cmd.ExecuteNonQuery();
SqlCommand cmd5 = new SqlCommand(
"insert into deceased_info(deceased_id, name_of_deceased, "
+ "address, do_birth, do_death, place_of_death, "
+ "date_of_interment, COD_id, place_of_vigil_id, "
+ "service_id, owner_id) values('"
+ ownerid
+ "','"
+ textBox9.Text
+ "', '"
+ textBox10.Text
+ "', '"
+ dateTimePicker1.Value.ToString("yyyyMMdd HH:mm:ss")
+ "', '"
+ dateTimePicker2.Value.ToString("yyyyMMdd HH:mm:ss")
+ "', '"
+ textBox11.Text
+ "', '"
+ dateTimePicker3.Value.ToString("yyyyMMdd HH:mm:ss")
+ "', '"
+ ownerid
+ "', '"
+ ownerid
+ "', '"
+ ownerid
+ "', '"
+ ownerid
+ "')",
con);
cmd.ExecuteNonQuery();
SqlCommand cmd6 = new SqlCommand(
"insert into interment_location(lot_no, block, section, "
+ "size, garden_id) values('"
+ ownerid
+ "','"
+ textBox12.Text
+ "', '"
+ textBox13.Text
+ "', '"
+ textBox14.Text
+ "', '"
+ ownerid
+ "')",
con);
cmd.ExecuteNonQuery();
MessageBox.Show(
"Your reservation has been made!",
"Reserve",
MessageBoxButtons.OK,
MessageBoxIcon.Information);
catch (Exception x)
MessageBox.Show(x.Message);
if (!rdr.IsClosed)
rdr.Close(); //close the datareader if it is not closed already
con.Close();
【讨论】：
我已经尝试过了，但我不断收到“对象引用未设置为对象的实例。 好的，刚刚解决了您的错误“已经有一个打开的 Datareader 关联.....”首先您将连接分配给打开 DataReader 的命令，然后您使用相同的连接用于插入记录。解决方法： 1. 插入记录前通过dr.Close()关闭datareader。 2.更改插入命令的连接对象。以上是关于C# 中已经有一个打开的 Datareader 关联的主要内容，如果未能解决你的问题，请参考以下文章
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