运行时程序报错：输入字符串格式不正确，谁来帮帮忙？

[supercsharp1]

try
{
string type=this.tyDownList.SelectedItem.Value;
string bookname=this.tyname.Text;
string author=this.tyAuthor.Text;
string translator=this.tyTranslator.Text;
string publisher=this.tyPublisher.Text;
string price=this.typrice.Text;
string discount=this.DiscountDownList.SelectedItem.Value;
string ImgName=Server.MapPath("\\webshop\\UpFile").ToString().Trim()+"\\"+ViewState["PostFileName"];
string introduce=this.TextBox1.Text;
string hits=this.tyHits.Text;
string sales=this.tySales.Text;
string status=this.DropDownList1.SelectedItem.Value;

mybook.AddBook(int.Parse(type),bookname,author,translator,publisher,double.Parse(price),double.Parse(discount),ImgName,introduce,int.Parse(hits),int.Parse(sales),int.Parse(status));
}

catch(Exception ex)
{
HttpContext.Current.Response.Write("<script type='text/javascript'>alert('"+ex.Message+"')</script>");

上面的mybook.AddBook即调用下面的：
--------------------------------------------------------------------------
public void AddBook(int type,string bookname,string author,string translator,string publisher,double price,double discount,string cover,string introduce,int hits,int sales ,int status)
{
try
{
string commstring="insert into Book (Type,BookName,Author,Translator,Publisher,price,Discount,Cover,Introduce,Hits,Sales,Status) values ("+type+",'"+bookname+"','"+author+"','"+translator+"','"+publisher+"',"+price+","+discount+",'"+cover+"','"+introduce+"',"+hits+","+sales+","+status+")";

sqldata.ExcuteDml(commstring);

}
catch(Exception ex)
{
HttpContext.Current.Response.Write("<script type='text/javascript'>alert('"+ex.Message+"')</script>");
}
}
}
上面的sqldata.ExcuteDml即调用下面的：
--------------------------------------------------------------------------

public void ExcuteDml(string commstring)
{
try
{
comm.CommandText = commstring;
comm.ExecuteNonQuery();
}

catch(Exception ex)
{
HttpContext.Current.Response.Write("<script type='text/javascript'> alert('"+ex.Message+"')</script>");
}
}

最后显示一个messagebox说输入字符串格式不正确，哪位高手来说说？