Save BLOB to disk as Image C#

Question

Hello,

I am developing a web application that calls web services developed by a third party to send/receive data from a clients database. I am building the application using ASP.NET 3.5 C#.

The way that they are providing me images is in BLOB format. I call their method and what I get back is a DataSet with 2 fields "logo_name" and "logo" which is the BLOB field. What I want to do is: Save the image locally on the disk (to minimize calls to their database in the future).

I have been playing around with a couple of different ways of doing this but cannot seem to get the image to save correctly. I have been able to create a file in a folder with the correct name but if I try to view the image it does not work.

I was hoping someone could give me some sample code to show me how to save a BLOB field to the local disk?

Here is the code I currently have

public static class ProductImages
    {


        public static string GetSchoolLogo(string schoolID, string printCodeID)
        {
            int v_length = 0;
            string v_file_name = "";
            byte[] v_file_data = null;

            try
            {

                //Declare Web Service Variables
                P_SERVICE.Service ldeService = new P_SERVICE.Service();
                //Authentication Header
                ldeService.AuthHeaderValue = CGlobal.GetAuthHeader(System.Web.HttpContext.Current.Session);
                P_SERVICE.CDataResultOfDataSet ldeResult = null;
                DataSet ds = new DataSet();

                ldeResult = ldeService.GetItemLogo(schoolID, printCodeID);
                ds = ldeResult.Value;

                if (ds.Tables[0].Rows.Count > 0)
                {
                    v_file_data = StrToByteArray(ds.Tables[0].Rows[0]["logo"].ToString().TrimEnd());
                    v_file_name = ds.Tables[0].Rows[0]["logo_name"].ToString().TrimEnd();
                    v_length = Convert.ToInt32(v_file_data.Length);

                    // Load the file in the Memory Stream
                    MemoryStream ms = new MemoryStream(v_file_data, 0, v_file_data.Length);
                    ms.Write(v_file_data, 0, v_file_data.Length);

                    // Open the file stream in ordre to save on the local disk
                    string path = HttpContext.Current.Server.MapPath("~/_imagecache/schoolLogos/").ToString();
                    FileStream fs = File.OpenWrite(path + schoolID + "/" + v_file_name);
                    fs.Write(v_file_data, 0, v_file_data.Length);
                    fs.Close();

                    // Return True if no errors occured
                    return "~/_imagecache/schoolLogos/" + schoolID + "/" + v_file_name;
                }
                else
                    return "~/images/noPhoto.gif";

           }

            catch (Exception ex)
            {

                throw new Exception(ex.Message.ToString());
                //return "~/images/noPhoto.gif";
            } 
        }

        // C# to convert a string to a byte array.
        public static byte[] StrToByteArray(string str)
        {
            System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
            return encoding.GetBytes(str);
        }
    }


}

When I get the Type of data being returned it returns System.String

Type t = ds.Tables[0].Rows[0]["logo"].GetType();
HttpContext.Current.Trace.Warn(t.FullName);

Thanks

Answer 1

Your line:

v_file_data = StrToByteArray(ds.Tables[0].Rows[0]["logo"].ToString().TrimEnd()); 

Should really be:

v_file_data = ds.Tables[0].Rows[0]["logo"] as Byte[];

The method you were using will not encode and decode the bytes in the same way.

Answer 2

Try this:

// replace this line:
//v_file_data = StrToByteArray(ds.Tables[0].Rows[0]["logo"].ToString().TrimEnd());

// with this block:
string base64string = ds.Tables[0].Rows[0]["logo"] as string;

if (base64string != null)
{
    v_file_data = System.Convert.FromBase64String(v_file_data);
}

Take the byte array and load it to file using the rest of your code.

HTH....

Answer 3

Ok, so it looks like the web service is doing you no favors. They really should be returning a byte array. but anyway, the string is definitely not base64 and definitely not ascii.

Lets try this wild stab in the dark:

v_file_data = Encoding.UTF8.GetBytes(ds.Tables[0].Rows[0]["logo"]);