Question

我应该建立软件健身房。我想在健身房为每位员工附上一张照片。所以我按照youtube上的优秀指南解释了如何将图像附加到数据。问题是，当我附上图片时，表格中的新行连接而不是现有的行

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;
using System.IO;


namespace gym
{
    public partial class Load_Save : Form
    {
        OleDbConnection DBConnection = new OleDbConnection();
        OleDbDataAdapter DataAdapter;
        DataTable LocalDataTable = new DataTable();

        int rowPosition=0;
        int rowNumber=0;


        public Load_Save()
        {
            InitializeComponent();
        }

        private void Load_Save_Load(object sender, EventArgs e)
        {
              ConnectToDatabase();  
        }

        private void ConnectToDatabase()
        {
            DBConnection.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" + Directory.GetCurrentDirectory() + "\\data.mdb";  

            DBConnection.Open();

            DataAdapter = new OleDbDataAdapter("Select * From Workers", DBConnection);

            DataAdapter.Fill(LocalDataTable);

            if(LocalDataTable.Rows.Count !=0)
            {
                rowPosition = LocalDataTable.Rows.Count;
            }
        }

        private void btnBrowse_Click(object sender, EventArgs e)
        {
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                pictureBox1.Image = Image.FromFile(openFileDialog1.FileName);
                btnSave.Enabled = true;

            }
        }

        private void btnSave_Click(object sender, EventArgs e)
        {
            StoreData(ConvertImageToBytes(pictureBox1.Image));
        }

        private byte[] ConvertImageToBytes(Image InputImage)
        {
            Bitmap BmpImage = new Bitmap(InputImage);

            MemoryStream Mystream = new MemoryStream();

            BmpImage.Save(Mystream, System.Drawing.Imaging.ImageFormat.Jpeg);

            byte[] ImageAsBytes = Mystream.ToArray();

            return ImageAsBytes;
        }

        private void StoreData(byte[] ImageAsBytes)
        {

            if(DBConnection.State.Equals(ConnectionState.Closed))
               DBConnection.Open();


            try
            {
                MessageBox.Show("Saving image at index: " + rowPosition.ToString());

                OleDbCommand oledbInsert = new OleDbCommand("Insert INTO Workers (id,firtsname,lastname,email,username,job,passw,permission,phone,dateofjoin,photo) VALUES('" + "','" + "','" + "','" + "','" + "','" + "','" + "','" + "','" + "','" + "',@Myphoto)", DBConnection);
                OleDbParameter imageParameter = oledbInsert.Parameters.AddWithValue("@photo", SqlDbType.Binary);
                imageParameter.Value = ImageAsBytes;
                imageParameter.Size = ImageAsBytes.Length;

                int rowsAffected = oledbInsert.ExecuteNonQuery();
                MessageBox.Show("data stored succ in" + rowsAffected.ToString() + " ROW");
                rowPosition++;

            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
                MessageBox.Show(ex.StackTrace.ToString());
            }
            finally 
            {
                RefreshDBCconnection();
            }
        }


        private void RefreshDBCconnection()
        {
            DBConnection.Close();
            LocalDataTable.Clear();
            ConnectToDatabase();
        }


    }

}

Answer 1

如果要更新数据库中已存在的内容，那么在SQL查询中，您必须使用UPDATE statement（ID为旧记录）而不是INSERT。像这样：

UPDATE Workers SET photo=@photo WHERE id=@old_id

或者作为变体（如果你想同时更新多个记录/多个字段并简化插入/更新代码，那么很好用） - 你可以BEGIN TRANSACTION删除旧记录＆＃34 ;删除＆＃34;，使用具有相同ID的INSERT插入新的，然后COMMIT TRANSACTION。

读取C＃winform中的MS Access数据库写入图像

1 个答案: