System.InvalidOperationException：连接未关闭。连接的当前速率是打开的，

Question

System.InvalidOperationException：连接未关闭。连接的当前速率是打开的，

软件未记录连接正在连接到 SQL 数据库，但未登录。请查看代码并帮助我提前谢谢

错误：

System.InvalidOPerationException：连接未关闭。连接的当前状态在 System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource'1 retry) 的 System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource'1 retry) 的 System.Data.ProvideBase.DBConnectionInternal.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskComletionsource'1 retry, DbConnectionOPtions userOPtions) 处打开。 Data.SqlClient.SqlConnection.TryOPenTaskCompletionSource'1 retry) at System.Data.Sqlclient.SqlConnection.OPen() at Login.LoginForm.Login() in D:\Downloads\Compressed\SchoolManaementSystem\SchoolManagementSystem\Login'Forms\Login.cs :第 67 行

public LoginForm()
{
    InitializeComponent();
    connection = new SqlConnection(ConfigurationManager.ConnectionStrings["CS"].ConnectionString);

}
#region Methods
//Method For Login Form
public void LoginTeacher()
{
    using (SqlConnection cnn = new SqlConnection(connectionString))
    {
        try
        {
            command = new SqlCommand("TeacherLogin", connection);
            command.CommandType = CommandType.StoredProcedure;
            connection.Open();
            command.Parameters.AddWithValue("@username", Txt_User.Text);
            command.Parameters.AddWithValue("@password", Txt_Pass.Text);

            SqlDataReader dataReader = command.ExecuteReader();

            if (dataReader.Read())
            {
                TeacherDash teacherDash = new TeacherDash();
                this.Hide();
                teacherDash.lblusertype.Text = dataReader[1] + " " + dataReader[2].ToString();
                teacherDash.ShowDialog();
                this.Close();
            }

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.ToString());
        }
        finally
        {
            cnn.Close();
        }
    }

}
public void Login()
{
    using (SqlConnection cnn = new SqlConnection(connectionString))
    {
        try
        {
            command = new SqlCommand("SP_USER_LOGIN", connection);
            command.CommandType = CommandType.StoredProcedure;
            connection.Open();
            command.Parameters.AddWithValue("@user", Txt_User.Text);
            command.Parameters.AddWithValue("@pass", Txt_Pass.Text);

            SqlDataReader dataReader = command.ExecuteReader();

            if (dataReader.Read())
            {
                LoginTeacher();
                if (dataReader[10].Equals("Admin"))
                {

                    AdminDash adminDash = new AdminDash();
                    this.Hide();
                    adminDash.lblusertype.Text = dataReader[1] + " " + dataReader[2].ToString();
                    adminDash.ShowDialog();

                    this.Close();
                }
                else if (dataReader[10].Equals("Teacher"))
                {
                    TeacherDash teacherDash = new TeacherDash();
                    this.Hide();
                    teacherDash.lblusertype.Text = dataReader[1] + " " + dataReader[2].ToString();
                    teacherDash.ShowDialog();
                    this.Close();
                }
                else if (dataReader[10].Equals("Accounts"))
                {
                    AccountsDash accountsDash = new AccountsDash();
                    this.Hide();
                    accountsDash.lblusertype.Text = dataReader[1] + " " + dataReader[2].ToString();
                    accountsDash.ShowDialog();

                    this.Close();
                }
                else if (dataReader[10].Equals("Addmission"))
                {
                    AdmissionDash admissionDash = new AdmissionDash();
                    this.Hide();
                    admissionDash.lblusertype.Text = dataReader[1] + " " + dataReader[2].ToString();
                    admissionDash.ShowDialog();
                    this.Close();
                }
            }
            else if (Txt_User.Text.Trim() == string.Empty & Txt_Pass.Text.Trim() == string.Empty)
            {
                MessageBox.Show("UserName And Password Fileds Empty", "Blank Field", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else if (Txt_User.Text.Trim() == string.Empty)
            {
                MessageBox.Show("Please Enter UserName", "UserName Blank", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            else if (Txt_Pass.Text.Trim() == string.Empty)
            {
                MessageBox.Show("Please Enter Password", "Password Blank", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            else
            {
                MessageBox.Show("Invalid UserName or Password", "Login Failed", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.ToString());
        }
        finally
        {
            cnn.Close();
        }
    }
}
        

#endregion

private void Btn_Login_Click(object sender, EventArgs e)
{
    LoginTeacher();
    Login();
}

private void pictureBox4_Click(object sender, EventArgs e)
{
    this.Close();
}

enter image description here

Answer 1

不要使用全局 connection 变量。

要确保连接始终关闭，请在using 块内打开连接，如以下代码片段所示。

这样做可确保在代码退出块时自动关闭连接。

using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();
        // Do work here; connection closed on following line.
    }

可以参考官方documentation。