c# - 不从数据库中检索数据

Question

我已经尝试构建并运行此代码，但它总是向我发送错误：'因为未从数据库中检索数据。

我的代码在构建后没有错误。我一直在搜索，但我看不出有什么问题。

我希望我能为这种情况找到一些答案。谢谢

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;


namespace WindowsFormsApplication1
{

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {    
        }

        private void listView1_SelectedIndexChanged(object sender, EventArgs e)
        {        
        }

        private void button1_Click(object sender, EventArgs e)
        {

            string ProviderName = null;
            string CatalogName = null;
            string DataSourceName = null;
            string ConnectionString = null;
            string CommandString = null;
            const int MaxRows = 100;

            ProviderName = "Provider=Something;";
            CatalogName = "Catalog=Something;";
            DataSourceName = "DataSource=Something";

            ConnectionString = ProviderName+CatalogName+DataSourceName;

            ////////////////////////////////////////////////////////////////////////////////

            CommandString = "Something";

            OleDbConnection DBConnection = null;
            try
            {
                DBConnection = new OleDbConnection(ConnectionString);
            }catch (Exception ex){

            MessageBox.Show("Error: Not connected. \n{0}", ex.Message);
                return;
            }

            try
            {
                OleDbCommand DBCommand = new OleDbCommand(CommandString, DBConnection);
                DBConnection.Open();


                OleDbDataReader DBReader = DBCommand.ExecuteReader();

                    /////////////////////////////////////////////////////////////////////////

                DateTime DBTimestamp = new System.DateTime();
                Double DBValue = new System.Double();
                int DBQualityCode;
                int DBFlags;
                String ColumnEntry;

                listView1.View = View.Details;
                listView1.GridLines = true;
                listView1.TabIndex = 0;
                listView1.Width = 400;

                listView1.Columns.Add(new ColumnHeader());
                listView1.Columns[0].Text = ("Timestamp");
                listView1.Columns[0].TextAlign = (HorizontalAlignment.Center);
                listView1.Columns[0].Width = 150;


                listView1.Columns.Add(new ColumnHeader());
                listView1.Columns[1].Text = ("Value");
                listView1.Columns[1].TextAlign = (HorizontalAlignment.Center);
                listView1.Columns[1].Width = 60;


                listView1.Columns.Add(new ColumnHeader());
                listView1.Columns[2].Text = ("Quality Code");
                listView1.Columns[2].TextAlign = (HorizontalAlignment.Center);
                listView1.Columns[2].Width = 60;


                listView1.Columns.Add(new ColumnHeader());
                listView1.Columns[3].Text = ("Flags");
                listView1.Columns[3].TextAlign = (HorizontalAlignment.Center);
                listView1.Columns[3].Width = 60;

                ListViewItem SingleRow;

                int count = 0;

                //////////////////////////////////////////////////////////////////////////

               while ((DBReader.Read() && (count < MaxRows)))
                {
                    DBTimestamp = DBReader.GetDateTime(1);
                    DBValue = DBReader.GetDouble(2);
                    DBQualityCode = DBReader.GetInt32(3);
                    DBFlags = DBReader.GetInt32(4);

                    //////////////////////////////////////

                    ColumnEntry = String.Format("{0:dd.MM.yy HH:mm:ss}{1:D2}", DBTimestamp, DBTimestamp.Millisecond);
                    SingleRow = new ListViewItem(ColumnEntry);

                    ColumnEntry = String.Format("{0:F}", DBValue);
                    SingleRow.SubItems.Add(ColumnEntry);

                    ColumnEntry = String.Format("{0:X2}", DBQualityCode);
                    SingleRow.SubItems.Add(ColumnEntry);

                    ColumnEntry = String.Format("{0:X4}", DBFlags);
                    SingleRow.SubItems.Add(ColumnEntry);

                    listView1.Items.Add(SingleRow);

                    count = count + 1;
               }
               DBReader.Close();
            }
            catch (Exception ex)
            {

                MessageBox.Show("Error:Failed to retrive Data From Database. \n{0}", ex.Message);
            }
            finally
            {

                DBConnection.Close();

            }    
                //////////////////////////////////////////////////

        }
    }
}