<%@ Page Title="" Language="VB" MasterPageFile="~/Admin/ADMIN.master" AutoEventWireup="false" CodeFile="EditSTUdetail.aspx.vb" Inherits="Admin_EditSTUdetail" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server">
<style type="text/css">
.auto-style1
{
height: 42px;
}
</style>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
<div align="center">
<fieldset>
<legend style="font-size: 16px;">SEARCH / EDIT / DELETE STUDENT RECORDS
</legend>
<div style="overflow: auto">
<div>
<asp:Label ID="lblMsg" runat="server" CssClass="lblresponse" />
<table style="margin: 3px auto 1px auto; height: 72px;">
<tr>
<td style="text-align: right;" class="auto-style2">Select Session/सत्र का चयन करें :
</td>
<td class="auto-style3">
<asp:DropDownList ID="ddlSession" runat="server" AppendDataBoundItems="True" Width="236px" Height="28px">
<asp:ListItem Text="--Select Session--" Value=""></asp:ListItem>
<asp:ListItem Text="" Value=""></asp:ListItem>
</asp:DropDownList>
</td>
<td>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="*" ControlToValidate="ddlSession" ForeColor="#990000"></asp:RequiredFieldValidator></td>
</tr>
<tr>
<td style="text-align: right;" class="auto-style1">Select Course /कक्षा का चयन करें :
</td>
<td>
<asp:DropDownList ID="ddlCourse" runat="server" AppendDataBoundItems="true" Width="236px" Height="28px">
<asp:ListItem Text="--Select Course--" Value=""></asp:ListItem>
<asp:ListItem Text="" Value=""></asp:ListItem>
</asp:DropDownList>
</td>
<td>
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ErrorMessage="*" ControlToValidate="ddlCourse" ForeColor="#990000"></asp:RequiredFieldValidator></td>
</tr>
<tr>
<td class="auto-style1"></td>
<td class="auto-style1">
<asp:Button ID="btnSearch" runat="server" Text="SEARCH" CssClass="button" OnClick="btnSearch_Click" Height="34px" Width="77px" /></td>
<td colspan="2" class="auto-style1">
<asp:Button ID="btnRefresh" runat="server" Text="REFRESH" CssClass="button" OnClick="btnRefresh_Click" Height="34px" Width="77px" /></td>
</tr>
</table>
</div>
</div>
<asp:GridView ID="GVdata" runat="server" Width="674px" CaptionAlign="Top"
AutoGenerateColumns="False" Height="100px" BackColor="White"
BorderColor="#999999" BorderStyle="None" BorderWidth="1px" CellPadding="3"
CellSpacing="2" GridLines="Vertical"
EmptyDataText="There Are No Record Found" OnRowCancelingEdit="gvManageOrders_RowCancelingEdit"
OnRowDeleting="gvManageOrders_RowDeleting" OnRowEditing="gvManageOrders_RowEditing"
OnRowUpdating="gvManageOrders_RowUpdating">
<AlternatingRowStyle BackColor="#DCDCDC" />
<Columns>
<asp:TemplateField HeaderText="Sr. No." ItemStyle-Width="20">
<ItemTemplate>
<asp:Label ID="lblRowNumber" Text='<%# Container.DataItemIndex + 1 %>' runat="server" />
</ItemTemplate>
</asp:TemplateField>
<asp:CommandField HeaderText="Edit/Remove" ShowDeleteButton="True"
ShowEditButton="True" DeleteText="Remove" />
<asp:TemplateField HeaderText="Student ID" Visible="True">
<ItemTemplate>
<asp:Label ID="studentID" runat="server" Text='<%# Bind("studentID")%>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Student Name" Visible="True">
<ItemTemplate>
<asp:Label ID="Sname" runat="server" Text='<%# Bind("Sname")%>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Father's Name" Visible="True">
<ItemTemplate>
<asp:Label ID="Fname" runat="server" Text='<%# Bind("Fname")%>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
</Columns>
<EmptyDataRowStyle BackColor="#eeeeee" BorderColor="Black"
BorderStyle="Solid" BorderWidth="1px" Font-Size="Large" ForeColor="#851010"
HorizontalAlign="Center" />
<FooterStyle BackColor="#CCCCCC" ForeColor="Black" />
<HeaderStyle BackColor="#851010" Font-Bold="True" ForeColor="White" />
<PagerStyle BackColor="#851010" ForeColor="Black" HorizontalAlign="Center" />
<RowStyle BackColor="#EEEEEE" ForeColor="Black" HorizontalAlign="Center" />
<SelectedRowStyle BackColor="#008A8C" Font-Bold="True" ForeColor="White" />
<SortedAscendingCellStyle BackColor="#F1F1F1" />
<SortedAscendingHeaderStyle BackColor="#0000A9" />
<SortedDescendingCellStyle BackColor="#CAC9C9" />
<SortedDescendingHeaderStyle BackColor="#000065" />
</asp:GridView>
</fieldset>
</div>
</asp:Content>
这是我的vb代码：
Imports System.Collections.Generic
Imports System.Configuration
Imports System.Data.SqlClient
Imports System.Globalization
Imports System.Linq
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Net.Mail
Imports System.Data
Imports System.ComponentModel
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms
Partial Public Class Admin_EditSTUdetail
Inherits System.Web.UI.Page
Private myds As DataSet
Protected Sub LoadSession()
Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("cmsDB").ConnectionString)
con.Open()
Dim com As New SqlCommand("select sessionID, session from tblcategories ORDER by session DESC", con)
Dim da As New SqlDataAdapter(com)
Dim ds As New DataSet()
da.Fill(ds)
ddlSession.DataTextField = ds.Tables(0).Columns("session").ToString()
' text field name of table dispalyed in dropdown
ddlSession.DataValueField = ds.Tables(0).Columns("sessionID").ToString()
' to retrive specific textfield name
ddlSession.DataSource = ds.Tables(0)
'assigning datasource to the dropdownlist
ddlSession.DataBind()
ddlSession.SelectedIndex = -1
'binding dropdownlist
End Sub
Protected Sub LoadCourse()
Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("cmsDB").ConnectionString)
con.Open()
Dim com As New SqlCommand("SELECT DISTINCT course AS mycolumn FROM " _
& " tblsubjects where course is not null and " _
& "not course = '' order by mycolumn", con)
Dim da As New SqlDataAdapter(com)
Dim ds As New DataSet()
da.Fill(ds)
ddlCourse.DataTextField = ds.Tables(0).Columns("mycolumn").ToString()
' text field name of table dispalyed in dropdown
ddlCourse.DataValueField = ds.Tables(0).Columns("mycolumn").ToString()
' to retrive specific textfield name
ddlCourse.DataSource = ds.Tables(0)
'assigning datasource to the dropdownlist
ddlCourse.DataBind()
ddlCourse.SelectedIndex = -1
'binding dropdownlist
End Sub
Protected Sub fillgrid()
Dim cn As New SqlConnection(ConfigurationManager.ConnectionStrings("cmsDB").ConnectionString)
Dim cmd As New SqlCommand("SELECT StudentID,session,course,Sname,Fname FROM [tblstudetail] WHERE " _
& " [session] = '" + ddlSession.SelectedValue.ToString() + "' AND " _
& " [course] = '" + ddlCourse.SelectedValue.ToString() + "'", cn)
cn.Open()
Dim da As New SqlDataAdapter(cmd)
myds = New DataSet()
da.Fill(myds)
GVdata.DataSource = myds
GVdata.DataBind()
End Sub
Private Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
If Not Page.IsPostBack Then
LoadSession()
LoadCourse()
fillgrid()
End If
End Sub
Protected Sub gvManageOrders_RowCancelingEdit(sender As Object, e As GridViewCancelEditEventArgs)
Throw New NotImplementedException
End Sub
Protected Sub gvManageOrders_RowDeleting(sender As Object, e As GridViewDeleteEventArgs)
Throw New NotImplementedException
End Sub
Protected Sub gvManageOrders_RowEditing(sender As Object, e As GridViewEditEventArgs)
Throw New NotImplementedException
End Sub
Protected Sub gvManageOrders_RowUpdating(sender As Object, e As GridViewUpdateEventArgs)
Throw New NotImplementedException
End Sub
Protected Sub btnSearch_Click(sender As Object, e As EventArgs) Handles btnSearch.Click
If Not Page.IsPostBack Then
fillgrid()
End If
End Sub
Protected Sub btnRefresh_Click(sender As Object, e As EventArgs) Handles btnRefresh.Click
GVdata.DataSource = Nothing
End Sub
End Class
但它没有归还我的要求。 请帮助我....
答案 0 :(得分：0)
请删除这些行，
ddlSession.SelectedIndex = -1
ddlCourse.SelectedIndex = -1
从LoadCourse和LoadSession方法的末尾开始。这些正在重置下拉值并导致问题。
流程在您的代码中搞砸了。您正在从页面加载方法中串行调用loadsession，loadcourses和fillgrid。想一想。当fillgrid中的代码执行时，下拉列表中没有选定的值。显然没有找到数据，所以gridview不可见。
更好的处理方法是引入两种新方法，
Protected Sub ddlCourses_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles ddlSession.SelectedIndexChanged
和
Protected Sub ddlAC3_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles ddlCourse.SelectedIndexChanged
在这些方法中发出对fillgrid的调用。 同样在fillgrid方法内部首先验证ddlCourse和ddlSession下拉列表中是否有一些值，然后发出数据库命令。
答案 1 :(得分：0)
首先
ddlSession.SelectedValue.ToString()
成为
ddlSession.SelectedValue
然后在Protected Sub中btnSearch_Click删除
If Not Page.IsPostBack Then
然后
ddlCourse.SelectedIndex = -1
成为
ddlCourse.ClearSelection();
最后，你确定数据库中没有NULL值吗？