单击按钮事件时更新数据库？

Question

当我的复选框被选中并单击验证按钮时，我无法更新我的数据库。注意：（我使用 Session 逐页传递我的数据）

在这个页面后面的另一个代码中，我向我的网格视图添加了一个列复选框。

   //Add a colum check row
    SubjectlistTable.Columns.Add("Check", Type.GetType("System.Boolean"));

    Session["ValidateSubject"] = SubjectlistTable;

    Response.Redirect("ValidateSubjectTeacher.aspx");

在ValidateSubjectTeacherPage中：

这是程序 ASP：

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="ValidateSubjectTeacher.aspx.cs" Inherits="SoftwareAnalysisAndDesign.SAD.ValidateSubjectTeacher" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Student Assessment Form</title>
    <meta charset="utf-8"/>
    <meta name="viewport" content="width=device-width, initial-scale=1"/>
    <link rel="stylesheet" href="Bootstrap/css/bootstrap-theme.css" />
    <link rel="stylesheet" href="Bootstrap/css/bootstrap.min.css"/> 
    <link rel="stylesheet" type="text/css" href="Stylesheets/ValidateSubjectTeacherStyle.css"/>

    <!--Side bar link-->
    <link rel="stylesheet" href="SidebarBootstrap/css/bootstrap.min.css" />
    <link rel="stylesheet" href="SidebarBootstrap/css/simple-sidebar.css" />
</head>
<body>
    <form id="form1" runat="server">
        <div class="headerwrapper">
            <div id="headercontent" class="jumbotron">
                <img id="img1" src="usjrlogo.png" />
                <h1 id="title">Online AppSess System</h1>
            </div>
        </div>

        <div class="container" style="text-align: center; margin: 0 auto;">
            <br />
            <h1>Validation of Subjects</h1>
            <br />
            <asp:GridView runat="server" CssClass="table table-hover table-bordered" ID="ValidateSubject" Style="text-align: center"></asp:GridView>
        </div>

        <div style="float: right; padding-right: 75px;">
            <button type="button" runat="server" class="btn btn-primary" onserverclick="ValidateSubject_Click">Validate</button>
            <button type="button" runat="server" class="btn btn-success" onserverclick="GoBackTeacher_Click">Go Back</button>
        </div>
    </form>

    <script src="jquery/jquery.min.js"></script>
    <script src="Bootstrap/js/bootstrap.min.js"></script>
</body>
</html>

背后的 Aspx 代码：

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

namespace SoftwareAnalysisAndDesign.SAD
{
    public partial class ValidateSubjectTeacher : System.Web.UI.Page
    {
        CheckBox check = new CheckBox();
        protected void Page_Load(object sender, EventArgs e)
        {
            if (Session["ValidateSubject"] == null)
            {
                Response.Redirect("TeacherPage.aspx", true);
            }

            if (!IsPostBack)
            {
                ValidateSubject.DataSource = Session["ValidateSubject"];
                ValidateSubject.DataBind();
            }
            //Add a checkbox in the last row of GridView Progmatically
            foreach (GridViewRow row in ValidateSubject.Rows)
            {
                check = row.Cells[row.Cells.Count - 1].Controls[0] as CheckBox; //position Check column on last row in gridview
                check.Enabled = true;
                check.CheckedChanged += ValidateSubject_Click; //Bind the event on the button
                check.AutoPostBack = true; //Set the AutoPostBack property to true
            }
        }
        protected void ValidateSubject_Click(object sender, EventArgs e)
        {
            CheckBox chk = (CheckBox)sender;
            GridViewRow grvRow = (GridViewRow)chk.NamingContainer;//This will give row


            string validated = "Validated";
            string notyetvalidated = "Not yet validated";
            string studid = grvRow.Cells[0].Text;
            string coursenum = grvRow.Cells[1].Text;

            if (chk.Checked)
            {
                grvRow.Cells[10].Text = validated;
                //Open Connection
                using (SqlConnection conn = new SqlConnection("Data Source=Keith;Initial Catalog=SAD;Integrated Security=True"))
                {
                    //Open Connection to database
                    try
                    {
                        conn.Open();
                    }
                    catch (Exception E)
                    {
                        Console.WriteLine(E.ToString());
                    }

                    using (SqlCommand cmd = new SqlCommand("Update AssessmentForm set Status = @Validated where StudentID = @studentID and CourseNo = @Coursenumber" ,conn))
                    {
                        cmd.Parameters.AddWithValue("@Validated", validated);
                        cmd.Parameters.AddWithValue("@studentID", studid);
                        cmd.Parameters.AddWithValue("@Coursenumber", coursenum);
                        cmd.ExecuteNonQuery();
                    }

                    //Close Connection to database
                    try
                    {
                        conn.Close();
                    }
                    catch (Exception E)
                    {
                        Console.WriteLine(E.ToString());
                    }
                }

            }
            else
            {
                grvRow.Cells[10].Text = notyetvalidated;
            }
        }
        protected void GoBackTeacher_Click(object sender, EventArgs e)
        {
            Response.Redirect("TeacherPage.aspx");
        }
    }
}

代码可以运行，但是当我点击提交按钮时，系统提示我一个错误，我无法更新我的数据库：

错误信息：

“System.InvalidCastException”类型的异常发生在 SoftwareAnalysisAndDesign.dll 但未在用户代码中处理 附加信息：无法转换类型的对象 'System.Web.UI.HtmlControls.HtmlButton' 键入 'System.Web.UI.WebControls.CheckBox'。

这里的复选框事件有问题：

CheckBox chk = (CheckBox)sender;

似乎无法同时处理复选框事件和按钮事件。 请帮忙，这是我要解决的唯一问题，以便我的系统完全正常工作。

相关链接Get specific data and update database

Answer 1

当您单击按钮时，您正在处理的“事件”不是来自 GridView 中的 CheckBox。它来自您的 <button> 元素。

您的应用程序的架构方式似乎不需要按钮 - 任何时候单击复选框以选择或取消选择它都会对该单行数据执行操作。所以不清楚当按钮被按下时你想要发生什么。

如果您愿意，您可以在同一方法中为这两个事件提供服务，方法是在开始时执行以下操作：

protected void ValidateSubject_Click(object sender, EventArgs e) {
    if ( sender.GetType().FullName == "System.Web.UI.WebControls.CheckBox" ) {
        // Have what you currently have for checkboxes here
    } else if ( sender.GetType().FullName == "System.Web.UI.HtmlControls.HtmlButton" ) {
        // Do something else for the button, probably involving getting the GridView's rows and iterating through them
    }
}

但我建议为单独的事件使用单独的事件处理程序。