Question

我有一个下拉列表，可以从数据库中获取一个学期列表。选择一个学期后，将显示该学期的课程下拉列表。选择课程后，将显示该课程的学生下拉列表。选择学生后，将显示一种分配分数信息。当我提交作业时，我想将学生DDL的值从SaveScore_Click函数传递给我的Grades.cs类。出于某种原因，enrollmentId（课程的学生）的值始终返回0.学生DDL正确填充所有学生ID。为什么这个值没有传递给我的Grades.calculate（）函数？

代码隐藏（AddScore.aspx.cs）

public partial class AddScore : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if(!IsPostBack)
                PopulateSemesterList();
        }
private void PopulateSemesterList()
        {
            string connstring;
            connstring = ConfigurationManager.ConnectionStrings["dbConn"].ConnectionString;
            SqlConnection conn = new SqlConnection(connstring);

            SqlCommand cmd = new SqlCommand("dbo.GetSemesters", conn);
            conn.Open();

            DDSemesters.DataSource = cmd.ExecuteReader();
            DDSemesters.DataTextField = "semesterName";
            DDSemesters.DataValueField = "semesterId";
            this.DataBind();

            conn.Close();
            conn.Dispose();

            DDSemesters.Items.Insert(0, new ListItem("Select Semester", "0"));
            DDSemesters.SelectedIndex = 0;
        }

        protected void DDSemesters_SelectedIndexChanged(object sender, EventArgs e)
        {
            DropDownList DDSemesters = sender as DropDownList;

            int selectedSemester = Convert.ToInt32(DDSemesters.SelectedItem.Value);

            string connstring;
            connstring = ConfigurationManager.ConnectionStrings["dbConn"].ConnectionString;
            SqlConnection conn = new SqlConnection(connstring);

            SqlCommand cmd = new SqlCommand("dbo.GetCourses", conn);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.Add(new SqlParameter("@semesterId", selectedSemester));

            conn.Open();

            DDCourses.DataSource = cmd.ExecuteReader();
            DDCourses.DataTextField = "courseName";
            DDCourses.DataValueField = "courseId";
            this.DataBind();

            conn.Close();
            conn.Dispose();

            DDCourses.Items.Insert(0, new ListItem("Select Course", "0"));
            DDCourses.SelectedIndex = 0;
            DDCourses.Visible = true;
            CoursesLbl.Visible = true;
        }

        protected void DDCourses_SelectedIndexChanged(object sender, EventArgs e)
        {
            DropDownList DDCourses = sender as DropDownList;

            int selectedCourse = Convert.ToInt32(DDCourses.SelectedItem.Value);

            string connstring;
            connstring = ConfigurationManager.ConnectionStrings["dbConn"].ConnectionString;
            SqlConnection conn = new SqlConnection(connstring);

            SqlCommand cmd = new SqlCommand("dbo.CourseEnrollment", conn);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.Add(new SqlParameter("@courseId", selectedCourse));

            conn.Open();

            DDStudents.DataSource = cmd.ExecuteReader();
            DDStudents.DataTextField = "fullName";
            DDStudents.DataValueField = "enrollmentId";
            this.DataBind();

            conn.Close();
            conn.Dispose();

            DDStudents.Items.Insert(0, new ListItem("Select Student", "0"));
            DDStudents.SelectedIndex = 0;
            DDStudents.Visible = true;
            StudentLbl.Visible = true;

        }

        protected void DDStudents_SelectedIndexChanged(object sender, EventArgs e)
        {
            assignmentInfoDiv.Visible = true;

        }

        protected void SaveScore_Click(object sender, EventArgs e)
        {
                Grades studentGrade = new Grades();
                studentGrade.enrollmentId = Convert.ToInt32(DDStudents.SelectedItem.Value);
                studentGrade.calculate();
                AssignmentError.Text = Convert.ToString(studentGrade.enrollmentId);               

        }

    }

AddScore.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="AddScore.aspx.cs" Inherits="midterm.AddScore" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Label ID="Label1" runat="server" Text="Select Semester"></asp:Label><br />
        <asp:DropDownList ID="DDSemesters" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DDSemesters_SelectedIndexChanged" DataTextField="semesterName" DataValueField="semesterId"></asp:DropDownList><br />

        <asp:Label ID="CoursesLbl" runat="server" Text="Select Course" Visible="false"></asp:Label><br />
        <asp:DropDownList visible="false" ID="DDCourses" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DDCourses_SelectedIndexChanged" DataTextField="courseName" DataValueField="courseId"></asp:DropDownList><br />

        <asp:Label ID="StudentLbl" runat="server" Text="Select Student" Visible="false"></asp:Label><br />
        <asp:DropDownList visible="false" ID="DDStudents" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DDStudents_SelectedIndexChanged" DataTextField="fullName" DataValueField="enrollmentId"></asp:DropDownList><br />

        <div id="assignmentInfoDiv" runat="server" visible="false" style="margin-top: 50px;">

            <asp:Label ID="studentName" runat="server" Text="Student Name" ></asp:Label>

            <asp:Label ID="AssignmentLbl" runat="server" Text="Assignment"></asp:Label><br />
            <asp:DropDownList ID="AssignmentList" runat="server">
                <asp:ListItem Text="Assignment 1"></asp:ListItem>
                <asp:ListItem Text="Assignment 2"></asp:ListItem>
                <asp:ListItem Text="Assignment 3"></asp:ListItem>
                <asp:ListItem Text="Assignment 4"></asp:ListItem>
                <asp:ListItem Text="Assignment 5"></asp:ListItem>
                <asp:ListItem Text="Assignment 6"></asp:ListItem>
                <asp:ListItem Text="Assignment 7"></asp:ListItem>
                <asp:ListItem Text="Assignment 8"></asp:ListItem>
                <asp:ListItem Text="Assignment 9"></asp:ListItem>
                <asp:ListItem Text="Assignment 10"></asp:ListItem>
                <asp:ListItem Text="Quiz 1"></asp:ListItem>
                <asp:ListItem Text="Quiz 2"></asp:ListItem>
                <asp:ListItem Text="Midterm Project"></asp:ListItem>
                <asp:ListItem Text="Final Project"></asp:ListItem>
            </asp:DropDownList>                
            <asp:Label ID="earnedLbl" runat="server" Text="Points Earned:"></asp:Label>
            <asp:TextBox ID="earnedTxt" runat="server"></asp:TextBox>

            <asp:Label ID="possibleLbl" runat="server" Text="Points Possible:"></asp:Label>
            <asp:TextBox ID="possibleTxt" runat="server"></asp:TextBox>

            <asp:Button ID="SaveScore" runat="server" Text="Save" OnClick="SaveScore_Click" />
            <asp:Label ID="AssignmentError" runat="server"></asp:Label>
        </div>
    </div>
    </form>
</body>
</html>

Grades.cs

public class Grades
    {
        public int pointsEarned;
        public int pointsPossible;
        public int totalEarned;
        public int totalPossible;
        public int percentage;
        public int courseId;
        public string enrollmentId;
        public string assignmentName;
        public string error;
        public string letterGrade;
        public double score;

        public void calculate()
        {
           return enrollmentId;

            }
        }

Answer 1

您好我认为您已经错过了下拉控制的Databind方法。

 DDSemesters.DataSource = cmd.ExecuteReader();
            DDSemesters.DataTextField = "semesterName";
            DDSemesters.DataValueField = "semesterId";
            this.DataBind();

这里this.DataBind（）方法来自System.Web.UI.Page.DataBind（）而不是你必须使用DDSemesters.DataBind（）为下拉列表绑定下拉列表，如下所示

 DDSemesters.DataSource = cmd.ExecuteReader();
            DDSemesters.DataTextField = "semesterName";
            DDSemesters.DataValueField = "semesterId";
            DDSemesters.DataBind();

Answer 2

我认为你的grade.cs应该是这样的

public class Grades
{
    public int pointsEarned;
    public int pointsPossible;
    public int totalEarned;
    public int totalPossible;
    public int percentage;
    public int courseId;
    public string strenrollmentId;
    public string assignmentName;
    public string error;
    public string letterGrade;
    public double score;
      public string enrollmentId;
       {
        get { return strenrollmentId; }
        set { strenrollmentId= value; }
       }
}

按钮点击应为

 protected void SaveScore_Click(object sender, EventArgs e)
    {
            Grades studentGrade = new Grades();
            studentGrade.enrollmentId = DDStudents.SelectedItem.Value;
            //studentGrade.calculate();
            AssignmentError.Text = studentGrade.enrollmentId;               

    }

为什么我的DropdownList值没有从我的代码隐藏传递到asp中的C＃类？

2 个答案: