how to encode and decode an uploaded image in base 64 in sql table

i must convert my uploaded images in base 64 to and from a sql table... my codes are as follow:

protected void ddlImage_SelectedIndexChanged(object sender, EventArgs e)
{
    string selectedValue = ddlImage.SelectedItem.Value;
    ShowImages(txtEmail.Text);
}

private void ShowImages(string email)
{
    string[] images = Directory.GetFiles(Server.MapPath("~/images/customers/" + email));
    ArrayList imageList = new ArrayList();
    foreach (string image in images)
    {
        string imageName = image.Substring(image.LastIndexOf(@"\") + 1);
        imageList.Add(imageName);
    }
    ddlImage.DataSource = imageList;
    ddlImage.DataBind();
}

protected void btnuploadimage_Click(object sender, EventArgs e)
{
    try
    {
        string folder = Server.MapPath("~/images/customers/" + txtEmail.Text);
        if (!Directory.Exists(folder))
        {
            Directory.CreateDirectory(folder);
        }
        string filename = Path.GetFileName(FileUpload1.FileName);
        FileUpload1.SaveAs(Server.MapPath("~/images/customers/" + txtEmail.Text + "/" + filename));               
        lblImage.Text = "image " + FileUpload1.FileName.ToString() + " successfully uploaded!";               
        Image1.ImageUrl = "~/images/customers/" + txtEmail.Text + "/" + filename;
    }
    catch (Exception)
    {
        lblImage.Text = "uppload Failed!";
    }
}

how i should put the encoded image to sql table and how i should decode it from sql table and put in Image1.ImageUrl??!!
appreciate your respond, more grateful if you give me the codes. kind regards