How do I check a BLOB field has Data or not?

Question

I am working on asp.net with oracle database. I want to print the image of employee which is saved in an old table. I don't even the data type of image saved in the photo field of that table.

I used Image handlers to print the images from newly created table but when I query on old tables the images is not getting printed.

How do I know that is there any image saved in the table?

If there is an image why it's not getting printed?

I'll show you the code for image handler for both the table (NEW , OLD) Image from newly created table is printing very fine but what's the problem in old one.

Can any give me any suggestions ?

Here is my ImgHandler.ashx code ;

 public void ProcessRequest (HttpContext context)
    {
        OracleDataReader rdr = null;
        OracleConnection conn = Conn.getConn();
        OracleCommand cmd = null;
        string ImgType = context.Request.QueryString["typ"].ToString();
        try
        {
            if (ImgType=="edu")//this is working fine
            {
                cmd = new OracleCommand("select attachment pic from newtbl where lvldcp_code=" + context.Request.QueryString["dcp"] + "and emp_code="+context.Request.QueryString["emp"], conn);
            }
            else if (ImgType=="profile")
            {
                cmd = new OracleCommand("select photo pic from oldtbl where emp_code="+context.Request.QueryString["emp"], conn);
            }

            conn.Open();
            rdr = cmd.ExecuteReader();
            while (rdr.Read())
            {
                context.Response.ContentType = "image/jpg";
                context.Response.BinaryWrite((byte[])rdr["pic"]);
            }
            if (rdr != null)
                rdr.Close();
        }
        catch (Exception ex)
        {

        }
        finally
        {
            if (conn != null)
                conn.Close();
        }


    }

Marcus Höglund · Answer 1 · 2016-05-27T06:52:58.260

0

If your queries are returning a blob field value then you could use the OracleBlob class.

public void ProcessRequest (HttpContext context)
{
    OracleDataReader rdr = null;
    OracleConnection conn = Conn.getConn();
    OracleCommand cmd = null;
    string ImgType = context.Request.QueryString["typ"].ToString();
    try
    {
        if (ImgType=="edu")//this is working fine
        {
            cmd = new OracleCommand("select attachment pic from newtbl where lvldcp_code=" + context.Request.QueryString["dcp"] + "and emp_code="+context.Request.QueryString["emp"], conn);
        }
        else if (ImgType=="profile")
        {
            cmd = new OracleCommand("select photo pic from oldtbl where emp_code="+context.Request.QueryString["emp"], conn);
        }

        Byte[] byteArray = null;
        OracleBlob blob;
        conn.Open();
        rdr = cmd.ExecuteReader();
        while (rdr.Read())
        {
            blob = rdr.GetOracleBlob(0);
            byteArray = new Byte[blob.Length];
            int i = blob.Read(byteArray, 0, System.Convert.ToInt32(blob.Length));

            //clob.Length or i > 0 will show if there are bites in the clob or not
        }
        if (rdr != null)
            rdr.Close();

        context.Response.ContentType = "image/jpg";
        context.Response.BinaryWrite(byteArray);
    }
    catch (Exception ex)
    {

    }
    finally
    {
        if (conn != null)
            conn.Close();
    }

}

edited May 27 '16 at 06:52

answered May 27 '16 at 06:22

Marcus Höglund

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ok, I thought you needed to specify it like ' select attachment as pic or select attachment "pic". Thanks for the info – Marcus Höglund May 27 '16 at 06:25
can you please specify the namespace for OracleLob ? – Alina Anjum May 27 '16 at 06:31
System.Data.OracleClient.OracleLob, I've used the unmanage version of oracle client. – Marcus Höglund May 27 '16 at 06:34
System.Data.OracleClient.OracleLob this namespace is not supported – Alina Anjum May 27 '16 at 06:35
What version of Oracle are you using? the client version – Marcus Höglund May 27 '16 at 06:37
– Alina Anjum May 27 '16 at 06:40
namespace for oracleblob ? – Alina Anjum May 27 '16 at 06:59
got the namespace using Oracle.DataAccess.Types; – Alina Anjum May 27 '16 at 07:00
yes i > 0 i checked it from breakpoint but the images is not yet prnted :( – Alina Anjum May 27 '16 at 07:12
Are images added to the blob image/jpg type? Could you add the c# code where you bind the .ashx to html components? – Marcus Höglund May 27 '16 at 07:24
– Alina Anjum May 27 '16 at 07:55
as this is very old database , i didn't added the images myself so i don't the type of image added – Alina Anjum May 27 '16 at 07:57
One way to test the current code is to add a new picture that you know is a image/jpg and then try to read that to the ashx. As you can se that you get the bytes from the blod then the issue may lay in that you formatting it to the wrong type. Test with different image types to get forward. – Marcus Höglund May 27 '16 at 08:07
Did you get any results? – Marcus Höglund May 31 '16 at 12:19

How do I check a BLOB field has Data or not?

1 Answers1