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POasp.net drop down list not selecting any value
 

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    <p>At btnSave - button event-handler, in the following two lines, SelectedValue is always returning null. </p> <pre><code>not.TargetSessionCode = this.sessionsDropDownList1.SelectedValue; not.CourseCode = this.coursesDropDownList1.SelectedValue; </code></pre> <p>Can anyone say why?</p> <p>This is my aspx code:</p> <pre><code>&lt;%@ Page Language="C#" MasterPageFile="~/MasterPage.Master" AutoEventWireup="true" CodeBehind="TeacherComposeNotice.aspx.cs" Inherits="Ice_Web_Portal_v_3_0_WebApplication.Teacher.TeacherComposeNotice" Title="Untitled Page" %&gt; &lt;asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server"&gt; &lt;table style="width: 270px"&gt; &lt;tr&gt; &lt;td style="text-align: right"&gt; Session:&lt;/td&gt; &lt;td colspan="2"&gt; &lt;asp:DropDownList ID="sessionsDropDownList1" runat="server" Width="178px"&gt; &lt;/asp:DropDownList&gt;&lt;/td&gt; &lt;td colspan="1" style="width: 6px"&gt; &lt;asp:Label ID="userNameLabel" runat="server" Text="usernameLabel" Width="167px"&gt;&lt;/asp:Label&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td style="text-align: right"&gt; Courses:&lt;/td&gt; &lt;td colspan="2"&gt; &lt;asp:DropDownList ID="coursesDropDownList1" runat="server" Width="178px"&gt; &lt;/asp:DropDownList&gt;&lt;/td&gt; &lt;td colspan="1"&gt;&lt;asp:Label id="labCourses" runat="server" Width="167px" Text="labCourses"&gt;&lt;/asp:Label&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td style="text-align: right"&gt; Subject:&lt;/td&gt; &lt;td colspan="3"&gt; &lt;asp:TextBox ID="mailSubjectTextBox" runat="server" Width="343px"&gt;&lt;/asp:TextBox&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td style="text-align: right" valign="top"&gt; Content:&lt;/td&gt; &lt;td colspan="3"&gt; &lt;asp:TextBox ID="mailContentTextBox" runat="server" Height="181px" Width="343px" Font-Names="Verdana"&gt;&lt;/asp:TextBox&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td style="text-align: right" valign="top"&gt; Expiry Date :&lt;/td&gt; &lt;td colspan="3"&gt; &lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td style="text-align: right" valign="top"&gt; &lt;/td&gt; &lt;td colspan="3" style="text-align: center"&gt; &amp;nbsp;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td style="text-align: right" valign="top"&gt; &lt;/td&gt; &lt;td colspan="3" style="text-align: left"&gt; &lt;asp:Label ID="errorMessageLabel" runat="server" ForeColor="#C00000" Text="***" Width="314px"&gt;&lt;/asp:Label&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td style="text-align: right" valign="top"&gt; &lt;/td&gt; &lt;td colspan="3" style="text-align: left"&gt; &lt;asp:Button ID="btnBack" runat="server" OnClick="btnBack_Click" Text="Back" /&gt; &lt;asp:Button ID="btnSave" runat="server" OnClick="btnSave_Click" Text="Save" /&gt;&lt;/td&gt; &lt;/tr&gt; &lt;/table&gt; &lt;/asp:Content&gt; </code></pre> <p>This is my code-behind:</p> <pre><code>public partial class TeacherComposeNotice : System.Web.UI.Page { string username = string.Empty; protected void Page_Load(object sender, EventArgs e) { username = (string)Request.QueryString["username"]; if (!IsPostBack) { LoadAllSessionsToDDL(); LoadAllCoursesToDDL(); } } private void LoadAllSessionsToDDL() { this.sessionsDropDownList1.Items.Clear(); List&lt;Ice_Web_Portal.BO.Session_&gt; items = Ice_Web_Portal.BO.Session_.GetAllSessions(); this.sessionsDropDownList1.DataSource = items; this.sessionsDropDownList1.DataTextField = "SessionName"; this.sessionsDropDownList1.DataValueField = "SessionCode"; this.sessionsDropDownList1.DataBind(); this.sessionsDropDownList1.SelectedIndex = 0; } private void LoadAllCoursesToDDL() { this.coursesDropDownList1.Items.Clear(); List&lt;Course&gt; items = Course.GetCourses(); this.coursesDropDownList1.DataSource = items; this.coursesDropDownList1.DataTextField = "CourseName"; this.coursesDropDownList1.DataValueField = "CourseCode"; this.coursesDropDownList1.DataBind(); } protected void btnBack_Click(object sender, EventArgs e) { Server.Transfer("~/Teacher/TeacherControlPanel.aspx?username=" + username); } protected void btnSave_Click(object sender, EventArgs e) { Ice_Web_Portal.BO.Teacher teacher = Ice_Web_Portal.BO.Teacher.GetTeacherByUsername(username); if (teacher != null) { Notice not = new Notice(); not.HangingDate = DateTime.Now; not.TeacherCode = teacher.TeacherCode; not.TargetSessionCode = this.sessionsDropDownList1.SelectedValue; not.CourseCode = this.coursesDropDownList1.SelectedValue; not.NoticeSubject = this.mailSubjectTextBox.Text; not.NoticeContent = this.mailContentTextBox.Text; not.ExpiryDate = DateTime.Now.AddMonths(1); not.IsExpired = false; bool success = Notice.Save(not); if (success) { errorMessageLabel.Text = "Saved"; } else { errorMessageLabel.Text = "Save failed"; } } else { //labErrorMessage.Text = "No teacher found"; } } } </code></pre>
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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