Question

我的项目允许管理员为军官档案添加奖章，目前我只能插入最多5枚奖牌。但是我的老师让我让管理员为官员简介插入尽可能多的奖章。我不知道如何检索管理员插入的所有图像，我知道如何使用varbinary将图像插入数据库。请给我这样做的方法。谢谢！

代码以下是我最多插入5枚奖牌的方式：

上传代码：

System.Drawing.Image uploaded = System.Drawing.Image.FromStream(FileUpload1.PostedFile.InputStream);

System.Drawing.Image newImage = new Bitmap(1024, 768);
using (Graphics g = Graphics.FromImage(newImage))
{
    g.InterpolationMode = InterpolationMode.HighQualityBicubic;
    g.DrawImage(uploaded, 0, 0, 1024, 768);
}

byte[] results;
using (MemoryStream ms = new MemoryStream())
{
    ImageCodecInfo codec = ImageCodecInfo.GetImageEncoders().FirstOrDefault(c => c.FormatID == ImageFormat.Jpeg.Guid);
    EncoderParameters jpegParms = new EncoderParameters(1);
    jpegParms.Param[0] = new EncoderParameter(Encoder.Quality, 95L);
    newImage.Save(ms, codec, jpegParms);
    results = ms.ToArray();
}

string sqlImage = "Insert into OfficerMedal(policeid, image) values ('" + Session["policeid"] + "', @Data)";
SqlCommand cmdImage = new SqlCommand(sqlImage);
cmdImage.Parameters.AddWithValue("@Data", results);
InsertUpdateData(cmdImage);

我使用aspx页面检索图像

protected void Page_Load(object sender, EventArgs e)
    {
        string strQuery = "select image from OfficerMedal where policeid='" + Session["policeid"] + "'";
        SqlCommand cmd = new SqlCommand(strQuery);
        DataTable dt = GetData(cmd);
        if (dt != null)
        {
            download(dt);
        }
    }

    private DataTable GetData(SqlCommand cmd)
    {
        DataTable dt = new DataTable();
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
        SqlDataAdapter sda = new SqlDataAdapter();
        cmd.CommandType = CommandType.Text;
        cmd.Connection = con;
        try
        {
            con.Open();
            sda.SelectCommand = cmd;
            sda.Fill(dt);
            return dt;
        }
        catch
        {
            return null;
        }
        finally
        {
            con.Close();
            sda.Dispose();
            con.Dispose();
        }
    }

    private void download(DataTable dt)
    {
        // check if you have any rows at all 
        // no rows -> no data to convert!
        if (dt.Rows.Count <= 0)
            return;

        // check if your row #0 even contains data -> if not, you can't do anything!
        if (dt.Rows[0].IsNull("image"))
            return;

        Byte[] bytes = (Byte[])dt.Rows[0]["image"];
        Response.Buffer = true;
        Response.Charset = "";
        Response.Cache.SetCacheability(HttpCacheability.NoCache);
        Response.ContentType = "image/jpg";
        Response.BinaryWrite(bytes);
        Response.End();
    }

要为此当前方法添加，我将从数据库中检索图像1。而不是检索属于该官员的所有图像。

Answer 1

通常的方法是使用HttpHandler而不是ASPX页面本身。处理程序负责从数据库中检索图像数据并将其作为图形输出;然后，它可以用作常规src标记的<img>或ImageUrl控件的<asp:image>属性。

添加处理程序的最简单方法是在“添加新项”对话框中选择“通用处理程序”： Add New Item

在处理程序的代码中，ProcessRequest是完成工作的方法，例如

public void ProcessRequest(HttpContext context)
{
    byte[] imageBytes;
    // Get the id of the image we want to show
    string imageId = context.Request.QueryString["ImageId"];

    // Get the image bytes out of the database
    using (SqlConnection conn = new SqlConnection(WebConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
    {
        // Pass in the image id we got from the querystring
        SqlCommand cmd = new SqlCommand("SELECT image FROM PoliceMedal WHERE ImageId=" + imageId, conn);
        conn.Open();
        SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
        reader.GetBytes(0, 0, imageBytes, 0, int.MaxValue);
    }

    context.Response.Buffer = true;
    context.Response.Charset = "";
    context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
    context.Response.ContentType = "image/jpg";
    context.Response.BinaryWrite(imageBytes);
    context.Response.End();
}

因此，我们的处理程序将从数据库返回图像数据，我们使用类似\ImageHandler.ashx?ImageId=1的URL来调用它。这确实需要更改您的数据库，因为您需要将一个密钥添加到PoliceMedal表中 - 我建议使用SQL Server IDENTITY列。

从您的问题中不清楚您是如何在ASPX页面上显示图像的，所以在这里我将向您展示如何将它们添加到PlaceHolder中。因此，我们将为一名官员检索一组图像ID，为每个人构建一个<asp:image>控件，并将图像添加到PlaceHolder。

protected void Page_Load(object sender, EventArgs e)
{
    using (
        SqlConnection conn =
            new SqlConnection(WebConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
    {
        // Query the table to get the list of image IDs for the current user
        SqlCommand cmd = new SqlCommand("SELECT ImageId FROM PoliceMedal WHERE policeid = " + Session["policeid"], conn);
        conn.Open();
        SqlDataReader imageReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);

        // For each image in the database
        while (imageReader.Read())
        {
            // Create the new Image control
            Image medalImage = new Image();
            // Call the handler, passing the id of the image in the querystring
            medalImage.ImageUrl = string.Format("ImageHandler.ashx?ImageId={0}",
                                                imageReader.GetInt32(0));
            // Add the image to the placeholder
            MedalPlaceHolder.Controls.Add(medalImage);
        }
    }
}

显示从数据库检索多个图像

1 个答案: