如何更新数据库中的图像？ 时间：2019-04-10标签：asp.netsql

Question

This is my code, which all works fine, so I don't want to change the way I'm doing it. However I'm at a loss as to what to do with the image. How do I display it for the user to edit, and then update their new upload to the database?

    protected void Page_Load(object sender, EventArgs e)
{

    if (!IsPostBack) { 
    int row = 0;
    if (Request.QueryString["Advertisement"] != null) {

        row = int.Parse(Request.QueryString["Advertisement"]);
    }
    else
    {
        Response.Redirect("ViewAdvertisements.aspx");
    }

    string connectionString = WebConfigurationManager.ConnectionStrings["ElmtreeConnection"].ConnectionString;

    SqlConnection myConnection = new SqlConnection(connectionString);

    myConnection.Open();

    string query = "SELECT * FROM Products WHERE Id=@rowid";

    SqlCommand myCommand = new SqlCommand(query, myConnection);

    myCommand.Parameters.AddWithValue("@rowid", row);

    SqlDataReader rdr = myCommand.ExecuteReader();

    while (rdr.Read())
    {
        editadtitle.Text = (rdr["name"].ToString());
        editdescription.Text = (rdr["description"].ToString());
        editprice.Text = (rdr["price"].ToString());
        editcategory.Text = (rdr["categoryid"].ToString());



    }



}
}

   protected void btnSignOut_Click(object sender, EventArgs e)
{
    Session["SELLER"] = null;
    Response.Redirect("Default.aspx");
}

protected void updatebutton_Click(object sender, EventArgs e)
{




    string connectionString = WebConfigurationManager.ConnectionStrings["ElmtreeConnection"].ConnectionString;

    SqlConnection myConnection = new SqlConnection(connectionString);


    myConnection.Open();

    string adtitleupdate = editadtitle.Text;
    int row = int.Parse(Request.QueryString["Advertisement"]);
    string descriptionupdate = editdescription.Text;
    string priceupdate = editprice.Text;
    string categoryupdate = editcategory.Text;



    string query = "UPDATE Products SET Name = @newadtitle, Description = @newdescription, Price = @newprice, CategoryId = @newcategory WHERE Id = @id";

    SqlCommand myCommand = new SqlCommand(query, myConnection);

    myCommand.Parameters.AddWithValue("@newadtitle", adtitleupdate);
    myCommand.Parameters.AddWithValue("@id",row);
    myCommand.Parameters.AddWithValue("@newdescription", descriptionupdate);
    myCommand.Parameters.AddWithValue("@newprice", priceupdate);
    myCommand.Parameters.AddWithValue("@newcategory", categoryupdate);





    updatelabel.Text = "Your information has now been updated. ";



    myCommand.ExecuteNonQuery();

    myConnection.Close();

}
 }

Answer 1

I prefer not to store the images in relational databases, because the imagedata (bytestreams) which you supposed to store are heavy.

You can create a repository on your server and store the images over there (dont forget to set appropriate permission for the user to access). While you create a product instead of storing the image save the location details.

Once you load the product details take the location from the database. :- Create a ASP.NET handler to load the images on the client browser. In Handler request the images from the repository and create BITMAP from the image data.

To display the images in browser add an IMG tag and give the source as Handlers/ImageHandler.ashxproductId={{productId}}&imageNo={{No}} as the query string. This will result to display the images.

To Upload new image and replace the existing one use the FileUpload to upload the image and replace the existing one with new one. So you dont need to update the database (but prefer to put some user audit to track and update).