如何從Access數據庫檢索數據

Question

當我運行以下代碼時，我收到錯誤

沒有為一個或多個必需參數給出值。

誰能說出為什么呢？

namespace ATMPROJECT
{
    public partial class pin : Form
    {
        public pin()
        {
            InitializeComponent();


        }

        private void button1_Click(object sender, EventArgs e)
        {
            OleDbConnection con= new OleDbConnection ();
            OleDbCommand cmd;

            DataSet ds;
            OleDbDataAdapter da;
            OleDbDataReader dr = null;
            string i;
             con = new OleDbConnection ( "Provider = Microsoft.ACE.OLEDB.12.0; Data Source =C:\\Users\\RELIABLE TRADING CO\\Documents\\atm.accdb ");
            con.Open();
            if (textBox1.Text == "")
            {
                label1.Text  = ("PLZ ENTER YOUR PIN FIRST");

            }
            else
            {

                ds = new DataSet();

                i = @"SELECT * from atm WHERE pin= ?";
                cmd = new OleDbCommand(i,con);


                 cmd.Parameters.Add("@pin",OleDbType.VarChar).Value = textBox1 .Text;
                 da = new OleDbDataAdapter(cmd);


                 MessageBox.Show("done");
                 da.Fill(ds);
                 dataGridView1.DataSource = ds;

// generates error (No value given for one or more required parameters.)

Answer 1

該錯誤表明您的atm表沒有名為pin的字段。

另外，您可能必須在數據源中指定表：

dataGridView1.DataSource = ds.Tables[0];