insert query executing when every time page got refreshing

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.IO;

public partial class ImageUpLoader : System.Web.UI.Page
{
    string sqlstr;
    static string path;
    string strFileName1;
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {

        }
    }

    public void uploadDocument()
    {

        if ((FileUpload1.PostedFile != null))
        {

            HttpPostedFile file1 = FileUpload1.PostedFile;
            path =  /* "Documents/" + */     file1.FileName;
            strFileName1 = Server.MapPath("~/Documents/") + file1.FileName;
            file1.SaveAs(strFileName1);

            string ext = Path.GetExtension(path);
            string contenttype = String.Empty;

            switch (ext)
            {
                case ".jpg":
                    contenttype = "image/jpg";
                    break;
                case ".png":
                    contenttype = "image/png";
                    break;
                case ".gif":
                    contenttype = "image/gif";
                    break;
                case ".pdf":
                    contenttype = "image/pdf";
                    break;
                //case ".doc":
                //    contenttype = "Documents/vnd.ms-word";
                //    break;
                //case ".docx":
                //    contenttype = "Documents/vnd.ms-word";
                //    break;
                //case ".xls":
                //    contenttype = "Documents/vnd.ms-excel";
                //    break;
                //case ".xlsx":
                //    contenttype = "Documents/vnd.ms-excel";
                //    break;

            }

        }

    }
    protected void btnUpload_Click(object sender, EventArgs e)
    {
        uploadDocument();
        string date = DateTime.Now.ToString("dd-MM-yyyy");
        string imageid = DAL.getRunningID("4");
        sqlstr = "insert into Images(ImageID,URL,DateTime)values(" + imageid + ",'" + path + "','" + date + "')";
        string sqlUpdate = "update Fms_Autonumber set RNo='" + imageid + "' where RCode='4'";
        List<string> ids = new List<string>();
        ids.Add(sqlstr);
        ids.Add(sqlUpdate);
        int j = DAL.sqlTransaction(ids);
        if (j > 0)
        {
            ScriptManager.RegisterStartupScript(this, this.GetType(), "Successfully Inserted", "alert('Image Uploaded Successfully..!')", true);
        }

        mltImageurl.Text = strFileName1;
    }
}