在C#中从Access数据库存储和检索图像 [英] Storing and retrieving images from an Access Database in C#

问题描述

我不是C#编程的新手，正在尝试创建一种软件，该软件将允许用户将信息和图片保存到Ms访问数据库中.我已经按照youtube上的教程进行操作，并设法存储了所需的信息和图片，但是我似乎无法检索图片并将其显示在图片框中.有人可以帮我吗?

Im new at C# programming and am trying to create a software that will allow the user to save information and a picture into a Ms access database. I have followed a tutorial on youtube and managed to store the info I needed and the picture but I cant seem to retrieve the image and display it in a picture box. can anyone help me?

我的代码是:

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 ConnectionApp
{
    public partial class ClinicaPrivada : Form
    {
        OleDbConnection DBConnection = new OleDbConnection();
        OleDbDataAdapter DataAdapter;
        DataTable LocalDatatable = new DataTable();
        int rowPosition = 0;
        int rowNumber = 0;


        public ClinicaPrivada()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            ConnectToDatabase();     
        }
        public void ConnectToDatabase()
        {
            DBConnection.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=ClinicaPrivada.mdb";
            DataAdapter = new OleDbDataAdapter("Select * From Pacientes", DBConnection);
            DataAdapter.Fill(LocalDatatable);
            if (LocalDatatable.Rows.Count != 0)
            {
                rowPosition = LocalDatatable.Rows.Count;
            }
        }

        public void RefreshDBConnection()
        {
            if (DBConnection.State.Equals(ConnectionState.Open))
            {
                DBConnection.Close();
                LocalDatatable.Clear();
                ConnectToDatabase();
            }
        }
        private void btnBrowse_Click(object sender, EventArgs e)
        {

        }

        public byte[] ConvertAndStoreToDB(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;
        }
        public void StoreToDB(byte[] ImageAsBytes)
        {
            string NrDoPaciente;
            NrDoPaciente = Convert.ToString(txtNrdoPaciente.Text);
            string Empresa;
            Empresa = Convert.ToString(txtEmpresa.Text);
            string DataDaConsutla;
            DataDaConsutla = Convert.ToString(txtDatadaConsulta.Text);
            if (DBConnection.State.Equals(ConnectionState.Closed))
                DBConnection.Open();
            try
            {
                MessageBox.Show("Saving Image at index:" + rowPosition.ToString());
                OleDbCommand insert = new OleDbCommand("Insert Into Pacientes (NrDoPaciente, Empresa, DatadaConsulta, Document) VALUES('" + NrDoPaciente +"','" + Empresa + "','" + DataDaConsutla + "','" + "Document"  + "')" , DBConnection);
                OleDbParameter InsertParameter = insert.Parameters.AddWithValue("Docu", SqlDbType.Binary);
                int rowsAffected = insert.ExecuteNonQuery();
                MessageBox.Show("Data Stored successfully in " + rowsAffected.ToString() + "Row");
                rowPosition++;

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

        }
        private Image ReadImageFromDB()
        {
            Image FetchedImg;

            if (rowNumber >= 0)
            {

                byte[] FetchedImgBytes = (byte[])LocalDatatable.Rows[rowNumber]["Document"];
                MemoryStream stream = new MemoryStream(FetchedImgBytes);
                FetchedImg = Image.FromStream(stream);
                return FetchedImg;
            }
            else
            {
                MessageBox.Show("There are no Images in the database yet. Please reconnect or add some images.");
                return null;
            }
        }

        private void btnBrowse_Click_1(object sender, EventArgs e)
        {
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                pictureBox1.Image = Image.FromFile(openFileDialog1.FileName);

            }

        }

        private void btnSave_Click_1(object sender, EventArgs e)
        {
            StoreToDB(ConvertAndStoreToDB(pictureBox1.Image));
        }

        private void btnDisplayAll_Click(object sender, EventArgs e)
        {
            RefreshDBConnection();

            rowNumber = 0;
            pictureBox2.Image = ReadImageFromDB();
            btnNext.Enabled = true;
            BtnPrevious.Enabled = true; 

        }





    }

}

推荐答案

您的内存中的图像可能超出范围. 这个问题，如果我是正确的，则直接相关.

Your image in memory is likely going out of scope. This question is directly related, if I am correct.

您必须对图像进行复制.否则，您的图像将链接到创建该图像的对象，并且当该对象超出范围时，图像数据将丢失.

You must make a copy of the image. Otherwise, your image is linked to the object that created it and when that object goes out of scope, your image data is lost.

我希望您会从尝试中获得例外.

I would expect you are getting exceptions from what you are trying to do.

顺便说一句，我同意建议避免使用MS Access的评论者.有很多更好的免费选项可供您选择.

BTW, I agree with the commenter who suggested avoiding MS Access. There are much better free options available to you.

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