How to insert and retrieve image from PostgreSql using C#

Question

I am trying to insert an image into Postgres and retrieve that image from postgresql using C#.

I have two columns in my table: memberid (character varying) and member_photo (bytea)

Here is my code to insert the image:

using (FileStream pgFileStream = new FileStream("D:\\Capture.jpg", FileMode.Open, FileAccess.Read))
{
    using (BinaryReader pgReader = new BinaryReader(new BufferedStream(pgFileStream)))
    {
        NpgsqlCommand command = new NpgsqlCommand();

        byte[] ImgByteA = pgReader.ReadBytes(Convert.ToInt32(pgFileStream.Length));
        command.CommandText = "insert into membermaster (memberid, member_photo) VALUES ('65', @Image)";
        command.Connection = Program.conn;

        Program.conn.Close();
        Program.conn.Open();

        //command.Parameters.Add(new NpgsqlParameter("Image", ImgByteA));
        command.Parameters.Add("@Image", ImgByteA).Value = ImgByteA;

        command.ExecuteNonQuery();

        Program.conn.Close();
    }
}

Here is my code to retrieve the image

NpgsqlCommand command = new NpgsqlCommand();
command.CommandText = "select member_photo from membermaster where memberid='65'";
command.Connection = Program.conn;

try
{
    Program.conn.Close();
    Program.conn.Open();

    byte[] productImageByte = command.ExecuteScalar() as byte[];

    if (productImageByte != null)
    {
        using (MemoryStream productImageStream = new System.IO.MemoryStream(productImageByte))
        {
            ImageConverter imageConverter = new System.Drawing.ImageConverter();
            pictureBox1.Image = imageConverter.ConvertFrom(productImageByte) as System.Drawing.Image;
            // image.Save(imageFullPath, System.Drawing.Imaging.ImageFormat.Jpeg);

            pictureBox1.Image = System.Drawing.Image.FromStream(productImageStream);
        }
    }
}
catch
{
    Program.conn.Close();
    throw;
}

The code to insert the image is working fine, but I can't show this image in a picturebox.

I get an error :

Parameter is not valid

Please help me solve this problem

Answer 1

AFAIK you cannot retrieve a byte[] using ExecuteScalar. You should use ExecuteReader instead. Just to be on the safe side when inserting parameters, I prefer to specify types myself, so my insert looks like this:

using (var conn = new NpgsqlConnection(connString))
{
    string sQL = "insert into picturetable (id, photo) VALUES(65, @Image)";
    using (var command = new NpgsqlCommand(sQL, conn))
    {
        NpgsqlParameter param = command.CreateParameter();
        param.ParameterName = "@Image";
        param.NpgsqlDbType = NpgsqlTypes.NpgsqlDbType.Bytea;
        param.Value = ImgByteA;
        command.Parameters.Add(param);

        conn.Open();
        command.ExecuteNonQuery();
    }
}

I can then retrieve and load the image like this:

using (var conn = new NpgsqlConnection(connString))
{
    string sQL = "SELECT photo from picturetable WHERE id = 65";
    using (var command = new NpgsqlCommand(sQL, conn))
    {
        byte[] productImageByte = null;
        conn.Open();
        var rdr = command.ExecuteReader();
        if (rdr.Read())
        {
            productImageByte = (byte[])rdr[0];
        }
        rdr.Close();
        if (productImageByte != null)
        {
            using (MemoryStream productImageStream = new System.IO.MemoryStream(productImageByte))
            {
                ImageConverter imageConverter = new System.Drawing.ImageConverter();
                pictureBox1.Image = imageConverter.ConvertFrom(productImageByte) as System.Drawing.Image;
            }
        }
    }
}

I do not know if specifying the datatype on insert makes any difference, so try just retrieving using a Reader first. If that doesn't work, then I suggest changing your insert routine to something like mine.

Please note in my example id is an integer, not a character varying!