How can i display gridview records based on multi selected dropdown items in asp.net

Question

In my application i have multi selected dropdownlist and based on selection i need to display in gridview. If i select two items from multi select dropdown based on that i need to display that two selected records on gridview.Below code is i selected two items i am getting first selection records only.
i tried code:

protected void ddlcol2_SelectedIndexChanged(object sender, EventArgs e)
{
    string qry = "select * from Collections where col1='" + ddlcol1.SelectedValue.ToString() + "' and col2='" + ddlcol2.SelectedValue.ToString() + "'";
    SqlCommand cmd = new SqlCommand(qry,con);
    DataTable dt = new DataTable();
    SqlDataAdapter sda = new SqlDataAdapter(cmd);
    sda.Fill(dt);            
    Gridview1.DataSource = dt;
    Gridview1.DataBind();
}

ddlcol2 is the multi select dropdown if i select two items from ddlcol2 i want to display that two items records on gridview.
Can anyone please tell me to how to do this.
Thank you

Answer 1

Assume that ddcol1 is single select only

change the query string to accept multiple values

string qry = "select * from Collections where col1='" + 
             ddlcol1.SelectedValue.ToString() + 
             "' and col2 in ('" + 
             string.Join("','", ddlcol2.Items.Cast<ListItem>
                                             .Where(i => i.Selected)
                                             .Select(i => i.Value)
                                             .ToArray()) + "')";

EDIT ( without LINQ )

var sCol2 = string.Empty;
foreach(var item in ddlcol2.Items)
{
    if (item.Selected)
        sCol2 += "'" + item.Value + "',"
}

// remove the last ,
if (sCol2.Length > 0)
    sCol2 = sCol2.Substring(0, sCol2.Length - 1);

string qry = "select * from Collections where col1 = '" +
             ddlcol1.SelectedValue.ToString() +
             "' and col2 in (" +
             sCol2 + ")";