Question

从comboBox中选择一个值后，我试图填充文本框。

我的代码运行良好，运行它时没有任何错误，但是当我从comboBox中选择一个值时，它不会填充文本框。请参阅下面的代码。

    private OleDbConnection connection = new OleDbConnection();

    public Form1()
    {
        InitializeComponent();
        connection.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\ASUS\Documents\appointment2.accdb";
    }

    private void Lastname_SelectedIndexChanged(object sender, EventArgs e)
    {

        try
        {
            connection.Open();
            OleDbCommand command = new OleDbCommand();
            command.Connection = connection;


            OleDbDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                string query = "select * from appointments where patientNo = '" + Lastname.Text + "' ";
                command.CommandText = query;

                Firstname.Text = reader["firstName"].ToString();
                patientNum.Text = reader["patientNo"].ToString();
                contactNum.Text = reader["contactNo"].ToString();

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

Answer 1

我看到两个紧迫的问题：

您将在发出CommandText方法后填充OleDbCommand对象的ExecuteReader属性，这意味着不评估任何SQL语句。

在发出ExecuteReader方法之前，应在之前填充SQL语句，即：

connection.Open(); OleDbCommand command = new OleDbCommand(); command.Connection = connection; command.CommandText = "select * from appointments where patientNo = '" + Lastname.Text + "' "; OleDbDataReader reader = command.ExecuteReader(); while (reader.Read()) { Firstname.Text = reader["firstName"].ToString(); patientNum.Text = reader["patientNo"].ToString(); contactNum.Text = reader["contactNo"].ToString(); } connection.Close();

您的SQL语句的where子句假设patientNo包含字符串数据，鉴于此字段的名称，该数据可能是错误的。

Answer 2

只需找出问题所在。将我的Lastname.Text与比较错误的值，并修复了代码的排列。谢谢大家的帮助。

            connection.Open();
            OleDbCommand command = new OleDbCommand();
            command.Connection = connection;
            command.CommandText = "select * from appointments where lastName = '" + Lastname.Text + "' ";
            OleDbDataReader reader = command.ExecuteReader();

            while (reader.Read())
            {
                Firstname.Text = reader["firstName"].ToString();
                patientNum.Text = reader["patientNo"].ToString();
                contactNum.Text = reader["contactNo"].ToString();

            }     

            connection.Close();

从comboBox中选择值后填充文本框

2 个答案: