String 无法将参数值从字符串转换为Int32 c

我有两个下拉列表：一个是省，一个是市，它们连接到DB。 我希望能够从第一个下拉列表中选择一个省，并能够看到 第二个下拉列表中该特殊省份的城市。 但我收到错误，无法将参数值从字符串转换为Int32。联机数据集ds1=新数据集

My DB: -------- _Province Prv_Id --- int (P.key) Prv_Name --- nvarchar -------------- _City Cty_Id --- int (P.key) Cty_Name --- nvarchar Cty_Prv_Id --- int (F.key) ---------------------------- ---------------------------- My ST.Procedures: ----------------------- ALTER PROCEDURE [dbo].[_City_selectItems] (@vari int) AS BEGIN SELECT * FROM _City WHERE (Cty_Prv_Id=@vari) END -------------------------------------------------- ALTER PROCEDURE [dbo].[_Province_selectAll] AS BEGIN SELECT * FROM _Province END --------------------------------------------------

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异常点处Label1.Text的值是多少。由于您正在页面加载上运行此代码，您的label1.text可能尚未初始化。label1仅用于检查。实际上，我不确定在DrpDwnProvince之后我在做什么。DataBind是否自动选择会引发IndexChange事件的索引。您可能需要检查DrpDwnProvince.Items.Count是否大于0，并设置SelectedIndex=0以强制加载Label1.Text。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;

namespace WebApplication3_DrpDwnListAndSQL
{
    public partial class WebForm2 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                func1();
                func2();
                //func3();
            }
        }

        protected void DrpDwnProvince_SelectedIndexChanged(object sender, EventArgs e)
        {
            Label1.Text =DrpDwnProvince.SelectedValue;
            //string a = DrpDwnProvince.SelectedValue;
        }




        //First function for Province DrpDwnList 
        private void func1()
        {
            SqlConnection con = new SqlConnection("Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=DrpBoxDB;Data Source=ARASH-PC");
            SqlDataAdapter com = new SqlDataAdapter("_Province_selectAll", con);
            com.SelectCommand.CommandType = CommandType.StoredProcedure;
            DataSet ds = new DataSet();
            if (com != null)
            { com.Fill(ds); }

            DrpDwnProvince.DataSource = ds;
            DrpDwnProvince.DataTextField = "Prv_Name";
            DrpDwnProvince.DataValueField = "Prv_Id";
            DrpDwnProvince.DataBind();
        }

        //Second function for City DrpDwnList
        private void func2()
        {
            SqlConnection con = new SqlConnection("Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=DrpBoxDB;Data Source=ARASH-PC");
            SqlDataAdapter com1 = new SqlDataAdapter("_City_selectItems", con);
            com1.SelectCommand.Parameters.Add("@vari",SqlDbType.Int).Value=Label1.Text;

            com1.SelectCommand.CommandType = CommandType.StoredProcedure;

            DataSet ds1 = new DataSet();
            if (com1 != null)
            { com1.Fill(ds1); }

            DrpDwnCity.DataSource = ds1;
            DrpDwnCity.DataTextField = "Cty_Name";
            DrpDwnCity.DataValueField = "Cty_Id";
            DrpDwnCity.DataBind();
        }

        //Third function for District DrpDwnList
       // private void func3()
       // {

      //  }


    }
}