怎么解决“ToString”方法没有采用“1”个参数的重载

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

protected void Button6_Click(object sender, EventArgs e)
{
this.TextBox11.Text =ToString(double.Parse(this.TextBox7.Text) + double.Parse (this.TextBox8.Text) + double.Parse(this.TextBox9.Text) + double.Parse(this.TextBox5.Text));
}

怎么修改呢？

this.TextBox11.Text =(double.Parse(this.TextBox7.Text) + double.Parse (this.TextBox8.Text) + double.Parse(this.TextBox9.Text) + double.Parse(this.TextBox5.Text)).ToString();

Tostring这样用就可以了。

试试model.prices.tostring("f3")，要判断model是否为空，不然会有异常