C＃作为数据库访问。如果选择Combobox，则文本框中的数据库值

Question

我有一个错误，其中显示连接未关闭 我甚至尝试过最后但是它不起作用

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    try
    {

        connection.Open();
        OleDbCommand command = new OleDbCommand();
        command.Connection = connection;
        string query = "SELECT * FROM Dataaa WHERE FirstName='" + comboBox1.Text + "'";
        command.CommandText = query;
        OleDbDataReader reader = command.ExecuteReader();
        while (reader.Read())
        {
            txt_EID.Text = reader["EID"].ToString();
            textBox1.Text = reader["Firstname"].ToString();
            textBox2.Text = reader["LastName"].ToString();
            textBox3.Text = reader["ICNO"].ToString();
            textBox4.Text = reader["Address"].ToString();
            textBox5.Text = reader["Loan"].ToString();
            textBox6.Text = reader["Percent"].ToString();
            textBox7.Text = reader["Payback"].ToString();
            textBox8.Text = reader["StartDate"].ToString();
            textBox9.Text = reader["EndDate"].ToString();
            textBox10.Text = reader["Monthly"].ToString();
            textBox11.Text = reader["PaymentType"].ToString();
            textBox12.Text = reader["Remark"].ToString();

        }
        connection.Close();
    }
    catch (Exception ex)
    {
        MessageBox.Show("error " + ex);
    }

Answer 1

而不是连接。手动关闭，在＆＃39;使用＆＃39;中创建连接。块：

using(var connection = new SqlConnection(...)) { OleDbCommand command = new OleDbCommand(); ........ }

这样您就不必担心关闭连接。一旦使用块结束，连接也会结束。