FileUpload--未将对象引用设置到对象的实例

private void ImageUpload()
    {
        DBOperation dbo = new DBOperation();
        pageFunction func = new pageFunction();


        string path = this.imageUpload.PostedFile.FileName;

        FileInfo image = new FileInfo(path);

        string name = image.Name;

        string type = image.Extension;


        if (".png" == type || ".PNG" == type || ".jpg" == type || ".JPG" == type || ".gif" == type || ".GIF" == type)
        {

            string savepath = Server.MapPath("Upload");

            this.imageUpload.SaveAs(savepath + "\\" + name);

            string dbpath = "../BgPage/Upload/" + name;
            dbo.InsertImage(dbpath);

            string insText = "";
            this.editArea.Text = this.editArea.Text + insText;
            func.WriteScipt(this.Page, "alert('上传成功!')");
        }
        else
        {
            func.WriteScipt(this.Page, "alert('不支持该图片类型,请选择gif、png或jpg类型的图片!')");
        }
    }

string path = this.imageUpload.PostedFile.FileName;
获取完整路径有问题，但是从代码上看我实在找不出错在什么地方