show data in gridview after selection from dropdown list - asp.net

Question

Hi i just want to show data in my gridview after selecting value from dropdown list and after selecting my dropdown list when i press on search button data can be seen in gridview. My gridview is connected with my database how can i do that my code is this:
aspx page:
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
CellPadding="4" DataSourceID="SqlDataSource1" ForeColor="#333333"
GridLines="None">
<AlternatingRowStyle BackColor="White" />
<Columns>
<asp:BoundField DataField="ID" HeaderText="ID" InsertVisible="False"
ReadOnly="True" SortExpression="ID" />
<asp:BoundField DataField="Portal" HeaderText="Portal"
SortExpression="Portal" />
<asp:BoundField DataField="TID" HeaderText="TID" SortExpression="TID" />
<asp:BoundField DataField="PNR" HeaderText="PNR" SortExpression="PNR" />
<asp:BoundField DataField="TicketNumber" HeaderText="TicketNumber"
SortExpression="TicketNumber" />
<asp:BoundField DataField="ESACCode" HeaderText="ESACCode"
SortExpression="ESACCode" />
<asp:BoundField DataField="WaiverCode" HeaderText="WaiverCode"
SortExpression="WaiverCode" />
<asp:BoundField DataField="Remarks" HeaderText="Remarks"
SortExpression="Remarks" />
<asp:BoundField DataField="UnusedTicketAmount" HeaderText="UnusedTicketAmount"
SortExpression="UnusedTicketAmount" />
<asp:BoundField DataField="ddlUnusedAmount" HeaderText="ddlUnusedAmount"
SortExpression="ddlUnusedAmount" />
<asp:BoundField DataField="AirlinePenality" HeaderText="AirlinePenality"
SortExpression="AirlinePenality" />
<asp:BoundField DataField="ddlAirlinePenality" HeaderText="ddlAirlinePenality"
SortExpression="ddlAirlinePenality" />
<asp:BoundField DataField="NetRefundProcess" HeaderText="NetRefundProcess"
SortExpression="NetRefundProcess" />
<asp:BoundField DataField="ddlNetRefundProcess"
HeaderText="ddlNetRefundProcess" SortExpression="ddlNetRefundProcess" />
<asp:BoundField DataField="RefundableCommission"
HeaderText="RefundableCommission" SortExpression="RefundableCommission" />
<asp:BoundField DataField="ddlRefundableCommission"
HeaderText="ddlRefundableCommission" SortExpression="ddlRefundableCommission" />
<asp:BoundField DataField="CouponRefunded" HeaderText="CouponRefunded"
SortExpression="CouponRefunded" />
<asp:BoundField DataField="RefundType" HeaderText="RefundType"
SortExpression="RefundType" />
<asp:BoundField DataField="DateTime" HeaderText="DateTime"
SortExpression="DateTime" />
</Columns>
<EditRowStyle BackColor="#2461BF" />
<FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
<HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
<PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
<RowStyle BackColor="#EFF3FB" />
<SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
<SortedAscendingCellStyle BackColor="#F5F7FB" />
<SortedAscendingHeaderStyle BackColor="#6D95E1" />
<SortedDescendingCellStyle BackColor="#E9EBEF" />
<SortedDescendingHeaderStyle BackColor="#4870BE" />
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:BartConnectionString %>"
SelectCommand="SELECT * FROM [Test]"></asp:SqlDataSource>
code on aspx.cs page
public void GridViewBind()
{
SqlCommand cmd = new SqlCommand("select * from Test where ID=" + DropDownList1.SelectedValue + "", con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds, "Test");
GridView1.DataSource = ds.Tables["Test"];
GridView1.DataBind();
}
protected void btnSearch_Click(object sender, EventArgs e)
{
this.GridViewBind();
}
After selecting value from my dropdown list Error : Invalid column name 'TRAVELONG'

Answer 1

Is ID a string? If so, you need inner quotes for the ID field:
SqlCommand cmd = new SqlCommand("select * from Test where ID='" + DropDownList1.SelectedValue + "'", con);
Otherwise, it may be considering the selected value as a column...