error on define grid view
<p>error is remove one grid view</p>

<pre><code>protected void dropdwnfilter_SelectedIndexChanged(object sender, EventArgs e)
{
    if (dropdwnfilter.SelectedItem.Value == "usd")
    {
        SqlCommand cmd = new SqlCommand(("Select name,prize*50,detail from product"), con);
        SqlDataAdapter adapter = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        adapter.Fill(ds);
        GridView1.DataSource = ds;
        GridView1.DataBind();
    }
    else
    {
        SqlCommand cmd = new SqlCommand(("Select * from product"), con);
        SqlDataAdapter adapter = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        adapter.Fill(ds);
        GridView1.DataSource = ds;
        GridView1.DataBind();
    }
}
</code></pre>

<p>I try this .basically wht i need if user go with usd(doller) then prize multiple with 50 and if he goes with another he get same prize</p>
