C#如何将数据从数据库获取到文本框

问候程序员

我在windows窗体中有一个组合框和一些文本框，它们连接到一个数据库。我的想法是，当组合框的值发生变化时，文本框中的数据也会发生变化。就像我在组合框中选择客户ID时，文本框将加载客户的数据，如全名或地址等。但当我打开表单时，组合框将消失，文本框保持为空。我正在使用Access数据库和Visual Studio 2012进行编码。这是我的密码。。

C#代码：

private void comboBox1_SelectedValueChanged(object sender, EventArgs e)
    {
        string pc = Convert.ToString(comboBox1.SelectedValue);
        string sql = "SELECT * FROM Customer WHERE CustomerID="+ pc;
        Data.Customer_Data(sql, pc);
        txtfullname.Text = Data.fullname;
        txtadress.Text = Data.adress;
        txtcity.Text = Data.city;
        txtemail.Text = Data.email;
    }

我的课叫数据：

public static string cs = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + Application.StartupPath + "''Database1.accdb";
public static string fullname = "";
public static string adress = "";
public static string city = "";
public static string email = "";
public static void Customer_Data(string sql, string pc)
    {
            if (pc == "")
            {
                return;
            }
            else
            {
                OleDbConnection oleDbConnection1 = new System.Data.OleDb.OleDbConnection(cs);
                oleDbConnection1.Open();
                OleDbCommand oleDbCommand1 = new System.Data.OleDb.OleDbCommand(sql,oleDbConnection1);
                OleDbDataReader reader = oleDbCommand1.ExecuteReader();
                if (!reader.Read())
                    return;
                fullname = reader["fullname"].ToString();
                adress = reader["adress"].ToString();
                city = reader["city"].ToString();
                email = reader["email"].ToString();

                oleDbConnection1.Close();
            }
    }