why is gridview not showing data on slecting a dropdown value

Question

User186897 posted

Hello

I have this aspx page and vb page...on selecting a value in dropdownlist i am unable to see any values in the grid?

    Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load

        If Not Me.IsPostBack Then
            Me.BindGrid()
        End If
    End Sub
    Private Sub BindGrid()
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Using con As New SqlConnection(constr)
            Using cmd As New SqlCommand("SELECT Id,SiteName,Email FROM Sites where Country=' " & DropDownList1.SelectedValue & "'")
                Using sda As New SqlDataAdapter()
                    cmd.Connection = con
                    sda.SelectCommand = cmd
                    Using dt As New DataTable()
                        sda.Fill(dt)
                        GridView1.DataSource = dt
                        GridView1.DataBind()
                    End Using
                End Using
            End Using
        End Using
    End Sub

 <div>
    
    
        <asp:DropDownList ID="DropDownList1" runat="server" autopostback="true" CssClass="auto-style2" DataSourceID="SqlDataSource1" DataTextField="Country" DataValueField="Country">
        </asp:DropDownList>
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:constr %>" SelectCommand="SELECT [Country] FROM [Sites]"></asp:SqlDataSource>
        <p>
            <asp:Button ID="Button1" autopostback="true" runat="server" CssClass="auto-style1" style="z-index: 1" Text="Button" />
        </p>
        
           
        <p>
            <asp:Button ID="Button2" runat="server" CssClass="auto-style4" Text="send email"  />
        </p>
        <asp:GridView ID="GridView1" runat="server" CssClass="auto-style3" AutoGenerateColumns="False">
            <Columns>
                <asp:TemplateField>
            <ItemTemplate>
                <asp:CheckBox ID="chkSelect" runat="server" />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="Id" HeaderText="Id" ItemStyle-Width="30" />
 
        <asp:BoundField DataField="SiteName" HeaderText="Name" ItemStyle-Width="150" />
        <asp:TemplateField HeaderText="Email">
            <ItemTemplate>
                <asp:HyperLink ID="lnkEmail" runat="server" Text='<%# Eval("Email") %>'  />
            </ItemTemplate>
        </asp:TemplateField>
            </Columns>
        </asp:GridView>
        </div>

Answer 1

User3690988 posted

I think that there are two reasons:

1. I think that your PostBack logic is backwards.  I would Bind if it is a PostBack.  Your logic will only load the GridView once.
2. Your SQL is inserting a space in the Country.  Change it to:

   Using cmd As New SqlCommand("SELECT Id,SiteName,Email FROM Sites where Country='" & DropDownList1.SelectedValue & "'")
    

(Get rid of the space in ... where Country=' ")
                                                                   ^

Answer 2

User-2057865890 posted

Hi Lexi85,

on selecting a value in dropdownlist i am unable to see any values in the grid?

You should use a SelectedIndexChanged event of a dropdownlist control by binding it with a database.

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" onselectedindexchanged="DropDownList1_SelectedIndexChanged">

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
   ...
}

reference:

Working With DropDownList SelectedIndexChanged Event

Gridview DropDownList Selected Index Changed Event & Get GridView Row Index

Best Regards,

Chris