Question

i’ve a blob field with (i presume) a PDF file.
How to convert and get the real file ?

Answer 1

Just amended this from code I’ve used before, judging by the code comments it’s copied from someone else but I’m not sure where. Definitely works unless I’ve just messed it up trying to make it generic!

private void WriteFiles() 
{

    SqlCommand cmd = new SqlCommand("SELECT FileName, FileData FROM ImageFiles", _conn);

    FileStream fs;                          // Writes the BLOB to a file
    BinaryWriter bw;                        // Streams the BLOB to the FileStream object.
    int bufferSize = 100;                   // Size of the BLOB buffer.
    byte[] outbyte = new byte[bufferSize];  // The BLOB byte[] buffer to be filled by GetBytes.
    long retval;                            // The bytes returned from GetBytes.
    long startIndex = 0;                    // The starting position in the BLOB output.

    // Open the connection and read data into the DataReader.
    _conn.Open();
    SqlDataReader myReader = cmd.ExecuteReader(CommandBehavior.SequentialAccess);

    if (!txtPath.Text.EndsWith("\\")) txtPath.Text += "\\";

    while (myReader.Read())
    {                
        // Create a file to hold the output.
        fs = new FileStream(txtPath.Text + myReader["FileName"].ToString().ToLower(),
                            FileMode.OpenOrCreate, FileAccess.Write);

        bw = new BinaryWriter(fs);

        // Reset the starting byte for the new BLOB.
        startIndex = 0;

        // Read the bytes into outbyte[] and retain the number of bytes returned.
        retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);

        // Continue reading and writing while there are bytes beyond the size of the buffer.
        while (retval == bufferSize)
        {
            bw.Write(outbyte);
            bw.Flush();

            // Reposition the start index to the end of the last buffer and fill the buffer.
            startIndex += bufferSize;
            retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);
        }

        // Write the remaining buffer.
        bw.Write(outbyte, 0, (int)retval);
        bw.Flush();

        // Close the output file.
        bw.Close();
        fs.Close();
    }
    // Close the reader and the connection.
    myReader.Close();
    _conn.Close();

}