Image size change and save

private string uploadMediumimg(string strid, string strLimage)//for uploading medium image
    {
        string fileName = "";
        string strSimg = "";
        if (strLimage != string.Empty)
        {
            string strExist = Server.MapPath("../Upload_largeimg/") + strLimage; //Server.MapPath("../Upload_largeimg") + "\\" + strLimage;
            Random randObj = new Random();
            string strName = Path.GetFileNameWithoutExtension(fileName) + "_M_" + randObj.Next(100).ToString() + strid;
            string strext = Path.GetExtension(strLimage);
            System.Drawing.Image imgPhotoVert = System.Drawing.Image.FromFile(strExist);
            imgPhotoVert = FixedSize(imgPhotoVert, 150, 150, "m");
            imgPhotoVert.Save(Server.MapPath("../Upload_mediumimg") + "/" + strName + strext);
            strSimg = strName + strext;
        }
        return strSimg;
    }