如何从mysql数据库在asp.net中设置图像。图像以 longblob 类型存储在数据库中

Question

在asp.net Web应用程序（不是MVC）中，我只是尝试从数据库存储和获取图像，我希望图像存储完美，但在检索时，我只看到一个空框。 让我给出下面的代码

aspx 文件

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <%--<img runat="server" id ="im" src="./"/>--%>
<asp:Image runat="server" id="imm" height="500px" Width="500px"/>

</asp:Content>

aspx.cs 文件

 public partial class Dashboard : System.Web.UI.Page
 {
     MySqlConnection connection;
     byte[] fileBytes;
     string connectionString;

     protected void Page_Load(object sender, EventArgs e)
     {
         string connectionString = "server=localhost;user=root;password=root;database=eshopping;";
         MySqlConnection connection = new MySqlConnection(connectionString);
         string query = "SELECT image FROM products WHERE id=3";

         MySqlCommand command = new MySqlCommand(query, connection);

         try
         {
             connection.Open();
             // Execute the query to fetch the image data
             object imageData = command.ExecuteScalar();

             if (imageData != null)
             {
                 // Convert the binary image data to a base64-encoded string
                 string base64String = Convert.ToBase64String((byte[])imageData);
                 // Set the src attribute of the im element with the base64-encoded string
                 imm.ImageUrl = "data:image/jpeg;base64," + base64String;
             }
         }
         catch (Exception ex)
         {
             // Handle any exceptions
             // For example, you can log the error or display a message to the user
             System.Console.WriteLine(ex.ToString());
         }
         finally
         {
             // Close the database connection
             connection.Close();
         }

     }

 }

下面是我存储图像的方式，我在这里犯了什么错误吗？

    protected void btnUpload_Click(object sender, EventArgs e)
{
    string name = Name.Text;
    string price = TextBox1.Text;
    string quantitqnty = TextBox2.Text;
    string description = dis.Value.ToString();
    if (fileUploadImage.HasFile && price!="" && quantitqnty!="" && description !="")
    {
         fileBytes = fileUploadImage.FileBytes;
        string query = "insert into products (name,price,quantity,discription,image) values ('"+name+"','"+price+"','"+quantitqnty+"','"+description+"','"+fileBytes+"')";
        MySqlCommand command = new MySqlCommand(query, connection);
        connection.Open();
        command.ExecuteNonQuery();
        connection.Close();
        ScriptManager.RegisterStartupScript(this, this.GetType(), "alert", "alert('Image Selected to upload');", true);
        Name.Text = "";
        TextBox1.Text = "";
        TextBox2.Text = "";
        dis.Value = "";
        Response.Redirect(Request.Url.AbsoluteUri);
    }
    else
    {
        ScriptManager.RegisterStartupScript(this, this.GetType(), "alert", "alert('Select a image');", true);


    }
}

当我在 sql workbench 中看到数据时，它只是将其显示为 BLOB

工作台图片在这里

这是我转换为base64string时得到的值

Answer 1

我不能对插入命令的字节数组使用字符串连接。

因此，您应该使用参数安全 SQL 来防止 SQL 注入，但更重要的是要确保保存字节数组。

将字节数组直接放入字符串中以用于插入命令？

在大多数情况下不起作用，因为此类二进制数据通常具有表示“字符串结尾”的字符，例如 ctrl-z，甚至是表示空终止字符串的 char(0)。因此，您不能使用简单的字符串将二进制数据插入数据库。

因此，请使用该插入的参数。

这是航空代码，但应该很接近：

    protected void btnUpload_Click(object sender, EventArgs e)
    {
        if (fileUploadImage.HasFile && price != "" && quantitqnty != "" && description != "")
        {

            byte[] fileBytes = fileUploadImage.FileBytes;

            string query =
                @"insert into products (name,price,quantity,discription,image) 
                values (@name, @price,@qty,@descript, @fileBytes)";

            using (MySqlConnection conn = new MySqlConnection(Properties.Settings.Default.MyDB))
            {
                conn.Open();
                using (MySqlCommand cmdSQL = new MySqlCommand(query, conn))
                {

                    cmdSQL.Parameters.Add("@name", MySqlDbType.String).Value = Name.Text;
                    cmdSQL.Parameters.Add("@price", MySqlDbType.Decimal).Value = TextBox1.Text;
                    cmdSQL.Parameters.Add("@qty", MySqlDbType.Int32).Value = TextBox2.Text;
                    cmdSQL.Parameters.Add("@descript", MySqlDbType.String).Value = dis.Value.ToString();
                    cmdSQL.Parameters.Add("@fileBytes", MySqlDbType.Blob).Value = fileBytes;

                    cmdSQL.ExecuteNonQuery();
                }
            }
            // ScriptManager.RegisterStartupScript(this, this.GetType(), "alert", "alert('Image Selected to upload');", true);
            //Name.Text = "";
            //TextBox1.Text = "";
            //TextBox2.Text = "";
            //dis.Value = "";
            // above code makes ZERO sennse if you going to have a redirect
            // (and above code will never run with a re-direct anyway)
            Response.Redirect(Request.Url.AbsoluteUri);
        }
    }