出现 "There is already an open DataReader associated with this Command which must be closed first" 错误

Question

即使我在 reader 上调用 close()，我仍然收到以下错误消息：

There is already an open DataReader associated with this Command which must be closed first

只有当有 2 个或更多空 Document_No 字段时才会发生。

if (textBoxDocNum.Text == "")
{
    SqlConnection baglanti = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=E:\Visual\sw\sw\DMSDataBase.mdf;Integrated Security=True");
    baglanti.Open();
    SqlCommand emir = new SqlCommand("SELECT Document_No, Doc_IDN FROM Details WHERE Document_No = ''", baglanti);
    DataTable dt = new DataTable();
    SqlDataAdapter da = new SqlDataAdapter(emir);
    da.Fill(dt);

    foreach (DataRow dr in dt.Rows)
    {
        SqlCommand emir2 = new SqlCommand("SELECT Class, Type, Title, State, Date, Status FROM Document WHERE IDN = "+dr["Doc_IDN"].ToString(), baglanti);
        SqlDataReader dr2 = emir2.ExecuteReader(); //it explodes here
        dr2.Read();
        if (dr2[0].ToString()==comboBoxClass.Text && dr2[1].ToString() == comboBoxType.Text && dr2[2].ToString() == textBoxTitle.Text && dr2[3].ToString() == State && dr2[5].ToString() == Status)
        {
            labelDuplicate.Visible = true;
            return 0;
        }
        dr2.Close();
        baglanti.Close();
    }
}

Answer 1

我认为您的问题可能是当您从 if 语句中 return 时，reader 不会关闭。

您应该更改代码以使用 using 语句。即使您 return，这也会关闭您的 reader。连接也是如此。

您的代码还有另一个缺陷。我相信 readers 需要一个开放的连接。如果条件为假，循环的第一遍将关闭连接，使第二遍失败。

出现 "There is already an open DataReader associated with this Command which must be closed first" 错误

Getting a "There is already an open DataReader associated with this Command which must be closed first" error

c#

sql

visual-studio

sqldatareader