我数据库中存的是string类型的  在实体中时Guid类型的

下面是转换成泛型时遇到的问题 的代码：

  PropertyInfo[] properties = typeof(CommedityClassesEntity).GetProperties();//获取实体类型的属性集合
            Hashtable hh = GetColumnType(dt.Columns);//属性名称和类型名的键值对集合
            IList<string> colNames = GetColumnNames(hh);//按照属性顺序的列名集合
            ListEntity<CommedityClassesEntity> list = new ListEntity<CommedityClassesEntity>();
              CommedityClassesEntity  model = default(CommedityClassesEntity);
            foreach (DataRow dr in dt.Rows)
            {
                model = new CommedityClassesEntity();//创建实体
                int i = 0;
                foreach (PropertyInfo p in properties)
                {
                    if (p.PropertyType == typeof(string))
                    {
                        p.SetValue(model, dr[colNames[i++]], null);
                    }
                    else if (p.PropertyType == typeof(int))
                    {
                        p.SetValue(model, int.Parse(dr[colNames[i++]].ToString()), null);
                    }
                    else if (p.PropertyType == typeof(DateTime))
                    {
                        p.SetValue(model, DateTime.Parse(dr[colNames[i++]].ToString()), null);
                    }
                    else if (p.PropertyType == typeof(float))
                    {
                        p.SetValue(model, float.Parse(dr[colNames[i++]].ToString()), null);
                    }
                    else if (p.PropertyType == typeof(double))
                    {
                        p.SetValue(model, double.Parse(dr[colNames[i++]].ToString()), null);
                    }
                    else if (p.PropertyType == typeof(Guid))
                    {
                        p.SetValue(model,new Guid(dr[colNames[i++]].ToString()), null); 这句话错误 我想问问 怎么想才正确
                    }
                }