WHERE與DropDownList的選定值

Question

條款我有這樣的下拉列表：

<asp:DropDownList ID="ddlEvents" runat="server" AppendDataBoundItems="True" 
    AutoPostBack="True" Width="140px"> 
    <asp:ListItem Value="0">Choose Location</asp:ListItem> 
    </asp:DropDownList> 

以上下拉列表選項動態地從數據庫中填充。

然後，我有這樣的代碼隱藏：

Public Sub BindGrid() 
     Dim oconn As New SqlConnection(sqlconn) 
     AddHandler ddlLocation.SelectedIndexChanged, New EventHandler(AddressOf ddl_SelectedIndexChanged) 
     oconn.Open() 
     Dim ocmd As New SqlCommand("select e.eventsId,e.Location, dbo.fnFormatDate(t.trainingDates, 'MON/DD/YYYY') t.eventDates, t.eventTime,t.eventDescription from tblEvents e, tblEventgDates t where e.eventid = t.eventid and e.eventid = " & ddlEvents.SelectedValue, oconn) 
     Dim oda As New SqlDataAdapter(ocmd) 
     Dim builder As New SqlCommandBuilder(oda) 
     Dim ds As New DataSet() 
     oda.Fill(ds) 
     gv1.DataSource = ds 
     gv1.DataBind() 

End Sub 

我們的用戶希望通過選擇下拉列表eventLocation來篩選結果，並只顯示與該位置相關聯的事件有。

上面的代碼沒有做任何事情。

我懷疑我需要selectedIndexChanged？

但是，如何將其納入BindData()事件？

感謝很多提前

Imports System.Collections.Generic 
Imports System.Linq 
Imports System.Web 
Imports System.Web.UI 
Imports System.Web.UI.WebControls 
Imports System.Data 
Imports System.Configuration 
Imports System.Data.SqlClient 

Partial Class Events 
    Inherits System.Web.UI.Page 
    Private sqlconn As String = ConfigurationManager.ConnectionStrings("DBConnectionString").ToString() 
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load 
     If Not IsPostBack Then 
      BindGrid() 
     End If 
     PopulateDates() 
    End Sub 
    Public Sub BindGrid() 
     Dim oconn As New SqlConnection(sqlconn) 
     ' AddHandler ddlEvents.SelectedIndexChanged, New EventHandler(AddressOf ddl_SelectedIndexChanged) 
     oconn.Open() 
     Dim ocmd As New SqlCommand("select e.eventsId,e.Location, dbo.fnFormatDate(t.trainingDates, 'MON/DD/YYYY') t.eventDates, t.eventTime,t.eventDescription from tblEvents e, tblEventgDates t where e.eventid = t.eventid and e.eventid = " & ddlEvents.SelectedValue, oconn) 
     Dim oda As New SqlDataAdapter(ocmd) 
     Dim builder As New SqlCommandBuilder(oda) 
     Dim ds As New DataSet() 
     oda.Fill(ds) 
     gv1.DataSource = ds 
     gv1.DataBind() 

    End Sub 

    Protected Sub gv1_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs) 
     Dim oconn As New SqlConnection(sqlconn) 
     oconn.Open() 
     Dim ocmd As New SqlCommand("SELECT* FROM Events", oconn) 
     Dim oda As New SqlDataAdapter(ocmd) 
     Dim builder As New SqlCommandBuilder(oda) 
     Dim ds As New DataSet() 
     oda.Fill(ds) 
     Dim ddl As DropDownList = DirectCast(e.Row.FindControl("ddlInstructors"), DropDownList) 
     If ddl IsNot Nothing Then 
      ddl.DataSource = ds 
      ddl.DataValueField = "EventsId" 
      ddl.DataTextField = "EventName" 
      ddl.DataBind() 
     End If 
     If e.Row.RowType = DataControlRowType.Footer Then 
      Dim ddldesig As DropDownList = DirectCast(e.Row.FindControl("ddladddesig"), DropDownList) 
      ddldesig.DataSource = ds 
      ddldesig.DataValueField = "EventsId" 
      ddldesig.DataTextField = "EventName" 

      ddldesig.DataBind() 
     End If 
    End Sub 

    Protected Sub gv1_RowDeleting(ByVal sender As Object, ByVal e As GridViewDeleteEventArgs) 
     Dim EID As Integer = Convert.ToInt32(gv1.DataKeys(e.RowIndex).Value) 
     Dim oconn As New SqlConnection(sqlconn) 
     oconn.Open() 
     Dim ocmd As New SqlCommand() 
     ocmd.CommandText = "DELETE FROM Events WHERE CourseID=@EID" 
     ocmd.Parameters.AddWithValue("@EID", EID) 
     ocmd.Connection = oconn 
     ocmd.ExecuteNonQuery() 
     oconn.Close() 
     BindGrid() 

    End Sub 

    Protected Sub gv1_RowEditing(ByVal sender As Object, ByVal e As GridViewEditEventArgs) 
     gv1.EditIndex = e.NewEditIndex 
     BindGrid() 
    End Sub 


    Protected Sub gv1_RowUpdating(ByVal sender As Object, ByVal e As GridViewUpdateEventArgs) 
     Dim EID As Integer = Convert.ToInt32(gv1.DataKeys(e.RowIndex).Value) 
     'Dim ENAME As String = DirectCast(gv1.Rows(e.RowIndex).Cells(1).FindControl("txtename"), TextBox).Text 
     Dim DESIGID As Integer = Integer.Parse(DirectCast(gv1.Rows(e.RowIndex).Cells(1).FindControl("ddlInstructors"), DropDownList).SelectedValue) 
     Dim oconn As New SqlConnection(sqlconn) 
     oconn.Open() 
     Dim ocmd As New SqlCommand() 
     ocmd.CommandText = "UPDATE MainEvents SET EventsId=@DESIGID WHERE CourseID=@EID " 
     ocmd.Parameters.AddWithValue("@EID", EID) 
     ocmd.Parameters.AddWithValue("@DESIGID", DESIGID) 
     ocmd.Connection = oconn 
     ocmd.ExecuteNonQuery() 
     gv1.EditIndex = -1 
     BindGrid() 
    End Sub 

    Protected Sub gv1_RowCancelingEdit(ByVal sender As Object, ByVal e As GridViewCancelEditEventArgs) 
     gv1.EditIndex = -1 
     BindGrid() 
    End Sub 
    Public Sub PopulateDates() 
     Dim cmd As New SqlCommand("Select EventsId, eventName from tblEvents order by location asc", New SqlConnection(ConfigurationManager.ConnectionStrings("DBConnectionString").ConnectionString)) 
     cmd.Connection.Open() 
     ddlEvents.Items.Clear() 
     Dim ddlValues As SqlDataReader 
     ddlValues = cmd.ExecuteReader() 

     ddlEvents.DataSource = ddlValues 
     ddlEvents.DataValueField = "EventsId" 
     ddlEvents.DataTextField = "EventName" 
     ddlEvents.DataBind() 

     cmd.Connection.Close() 
     cmd.Connection.Dispose() 
    End Sub 
    Protected Sub GridView1_RowUpdated(ByVal sender As Object, ByVal e As GridViewUpdatedEventArgs) 

     ' Indicate whether the update operation succeeded. 
     If e.Exception Is Nothing Then 
      Dim index As Integer = gv1.EditIndex 
      Dim row As GridViewRow = gv1.Rows(index) 
      Message.Text = "Row updated successfully'!" 
     Else 
      e.ExceptionHandled = True 
      Message.Text = e.Exception.Message 
     End If 
    End Sub 
End Class 

Answer 1

我已經解決了這個問題，並希望分享它，以防將來幫助其他人。

新增onselectedindexchanged的下拉列表

<asp:DropDownList ID="ddlEvents" runat="server" AutoPostBack="True" Width="140px" onselectedindexchanged="ddlEvents_SelectedIndexChanged" > 
    <asp:ListItem Value="0">Choose Location</asp:ListItem> 
    </asp:DropDownList> 

創造了SelectedIndexChange子，並呼籲BindGrid分從那裏：

Protected Sub ddlEvents_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) 
     BindGrid() 
    End Sub 

而且它解決了我的問題。

Answer 2

直接回答你的問題，採取了在BindGrid的addHandler操作代碼（）。添加參數BindGrid（）選定的指數變化事件所需，及導線上事件標記：

<asp:DropDownList ID="ddlEvents" runat="server" AppendDataBoundItems="true" AutoPostBack="true" OnSelectedIndexChanged="BindGrid"> 
      <asp:ListItem Value="0">Choose Location</asp:ListItem> 
     </asp:DropDownList> 


    Public Sub BindGrid(ByVal Sender As Object, ByVal e As EventArgs) 
     Dim oconn As New SqlConnection(sqlconn)   
     oconn.Open() 
     Dim ocmd As New SqlCommand("select e.eventsId,e.Location, dbo.fnFormatDate(t.trainingDates, 'MON/DD/YYYY') t.eventDates, t.eventTime,t.eventDescription from tblEvents e, tblEventgDates t where e.eventid = t.eventid and e.eventid = " & ddlEvents.SelectedValue, oconn) 
     Dim oda As New SqlDataAdapter(ocmd) 
     Dim builder As New SqlCommandBuilder(oda) 
     Dim ds As New DataSet() 
     oda.Fill(ds) 
     gv1.DataSource = ds 
     gv1.DataBind() 
    End Sub 

不過，我想提出一個更簡單的解決方案。您根本不需要處理SelectedIndexChanged，以便將其用作查詢參數。馬克它是這樣的：

<asp:DropDownList ID="ddlEvents" runat="server" AppendDataBoundItems="true" AutoPostBack="true" > 
     <asp:ListItem Value="0">Choose Location</asp:ListItem> 
</asp:DropDownList> 

標記您的網格像這樣用的DataSourceID指一個SqlDataSource（如下圖所示）：

​​

最後創建網格一個SqlDataSource並用它配置參數（防止SQL注入攻擊），可以自動從您的DropDownList拉：

<asp:SqlDataSource runat="server" 
SelectCommand="SELECT e.eventsId, e.Location, fnFormatDate(t.trainingDates, 'MON/DD/YYYY') t.eventDates, t.eventTime,t.eventDescription from tblEvents e, tblEventgDates t where e.eventid = t.eventid and e.eventid = @eventId)"> 
<SelectParameters> 
    <asp:ControlParameter ControlID="ddlEvents" PropertyName="SelectedValue" Name="@eventId" /> 
</SelectParameters>    

現在，當用戶從DropDownList中選擇時，網格會自動重新查詢並綁定數據。