将图像存储在数据库中并进行检索

本文关键字：检索 数据库 图像 存储 | 更新日期: 2023-09-27 18:22:06

我在数据库中插入图像的代码如下：

MemoryStream ms =new MemoryStream();
byte[] PhotoByte=null;
PhotoByte=ms.ToArray();
pictureBox1.Image.Save(ms, ImageFormat.Jpeg);
PhotoByte =ms.ToArray();
Str = "insert into Experimmm Values('" + PhotoByte + "','" + textBox1.Text + "')";
Conn.Open();
cmd.Connection = Conn;
cmd.CommandText = Str;
cmd.ExecuteNonQuery();
Conn.Close();

进展顺利。我可以在ma数据库表中看到二进制数据，如<Binary Data>我检索数据的代码是：

Str ="select * from Experimmm where id = '" +textBox2.Text + "'";
Conn.Open();
cmd.Connection = Conn;
cmd.CommandText = Str;
dr = cmd.ExecuteReader();
if (dr.Read())
{ label1.Text = dr.GetValue(1).ToString();
byte[] PhotoByte = (byte[])dr.GetValue(0);
MemoryStream mem = new MemoryStream(PhotoByte, 0, PhotoByte.Length);
//but an error takes place on next line "Parameter is not valid."             
pictureBox2.Image = Image.FromStream(mem);
} Conn.Close();

我使用的是visual studio 10，C#，sql server 2005

将图像存储在数据库中并进行检索

您的代码有几个问题。我会一行一行地解决：

MemoryStream ms =new MemoryStream();
byte[] PhotoByte=null;
PhotoByte=ms.ToArray();
pictureBox1.Image.Save(ms, ImageFormat.Jpeg);
PhotoByte =ms.ToArray();

虽然这不是问题，但你在这里有不必要的作业。上面的代码可以用这种方式写得更清楚：

MemoryStream ms =new MemoryStream();
pictureBox1.Image.Save(ms, ImageFormat.Jpeg);
byte[] PhotoByte =ms.ToArray();

接下来，下面的代码不使用参数始终，始终，始终参数化SQL查询，而不是动态构建SQL。不，说真的，总是。是的，即便如此（还有，Str变量是什么？某种可重用的实例变量？不要这样做。）

Str = "insert into Experimmm Values('" + PhotoByte + "','" + textBox1.Text + "')";
Conn.Open();
cmd.Connection = Conn;
cmd.CommandText = Str;
cmd.ExecuteNonQuery();
Conn.Close();

相反，它应该是这样的：

Conn.Open();
using(SqlCommand cmd = connection.CreateCommand())
{
    cmd.CommandText = "insert into Experimmm (column list) values(@data, @name)";
    cmd.Parameters.Add("@data", SqlDbType.VarBinary).Value = PhotoByte;
    cmd.Parameters.Add("@name", SqlDbType.VarChar, yourlength).Value = textBox1.Text;
    cmd.ExecuteNonQuery();
}
Conn.Close();

接下来，我们将继续检索。再次使用Str变量，不要做这种事情。此外，您还需要参数化此查询。

byte[] data;
string name;
Conn.Open();
using(SqlCommand cmd = Conn.CreateCommand())
{    
    cmd.CommandText = "select column_list from Experimmm where id = @id";
    cmd.Parameters.Add("@id", SqlDbType.VarChar, field_length).Value = textBox2.Text;
    using(SqlDataReader dr = cmd.ExecuteReader())
    {
        if (dr.Read())
        {
            data = (byte[])dr.GetValue(0); 
            name = (string)dr.GetValue(1);
        }
    }
}
Conn.Close();
label1.Text = name;
pictureBox2.Image = Image.FromStream(new MemoryStream(data));

当然可以将图像存储在数据库中。但不建议使用。最好将它们存储在文件系统中。

你的代码有点乱。下面是一个更好的例子。

MemoryStream ms =new MemoryStream(); 
byte[] PhotoByte=null; 
pictureBox1.Image.Save(ms, ImageFormat.Jpeg); 
PhotoByte =ms.ToArray(); 
// I'm not sure whether you are able to create an sql by simply concating the string
Str = "insert into Experimmm Values('@PhotoBytes','@MyTextValue')"; 
// You have to parametrize your query
cmd.Parameters.AddWithValue("PhotoBytes", PhotoByte);
// This also helps you to avoid syntactical corruption in case of ' and sql injection
cmd.Parameters.AddWithValue("MyTextValue", textBox1.Text );
Conn.Open(); 
cmd.Connection = Conn; 
cmd.CommandText = Str; 
cmd.ExecuteNonQuery(); 
Conn.Close();

当你检索时，你可以在一些处理程序中使用二进制写入程序

namespace TestNS
{
   public class MyHttpHandler : IHttpHandler
   {
      // Override the ProcessRequest method.
      public void ProcessRequest(HttpContext context)
      {
         // Your preparations, i.e. querystring or something
         var conn = new SqlConnection("Your connectionstring");
         var command = new SqlCommand("Your sql for retrieval of the bytes", conn);
         conn.Open();
         var data = (Byte[])command.ExecuteScalar();
         conn.Close();
         context.Response.BinaryWrite(data);      }
      public Boolean IsReusable
      {
         get { return false; }
      }
   }
}

OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=D:'KUTTY'Real_Project'Royalty_Pro'DbRoyalty_Access'Buzz_Loyalty.mdb");
DataSet ds = new DataSet();
con.Open();
OleDbCommand cmd = new OleDbCommand("select pic from test_table where id_image='123'",con);
OleDbDataAdapter da=new OleDbDataAdapter(cmd);
da.Fill(ds,"test_table");
//con.Close();
//ds = new DataSet();
//da.Fill(ds, "test_table");
FileStream FS1 = new FileStream("image.jpg", FileMode.Create);
if (ds.Tables["test_table"].Rows.Count > 0)
{
    byte[] blob = (byte[])ds.Tables["test_table"].Rows[0]["pic"];
    FS1.Write(blob, 0, blob.Length);
    FS1.Close();
    FS1 = null;
    byte[] imageData = (byte[])cmd.ExecuteScalar();
    MemoryStream ms = new MemoryStream(imageData, 0, imageData.Length);
    pictureBox2.Image = Image.FromStream(ms);

    pictureBox2.Image = Image.FromFile("image.jpg");
    pictureBox2.SizeMode = PictureBoxSizeMode.StretchImage;
    pictureBox2.Refresh();
    pictureBox2.Image = Image.FromStream(new MemoryStream(blob));  
    pictureBox2.Image = Image.FromFile("image.jpg");
    pictureBox2.SizeMode = PictureBoxSizeMode.StretchImage;
    pictureBox2.Refresh();
}

您应该使用参数化查询，而不是连接SQL字符串。

除了修复明显的SQL注入漏洞外，这将使您能够正确地将映像插入数据库。

关于如何插入SQL Server映像/二进制字段，有很多问题和答案——您应该看看它们。

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