how can select multiple rows from gridview and store in array in asp.net c#

I wrote code for asp.net c#

I use grid view to display information from database and I am using checkbox to select the data , but the problem How can save these data I selected in array , then save it to data base .

this my code

the grid view

            <Columns>

                <asp:TemplateField HeaderText="Select">

                    <ItemTemplate>

                        <asp:CheckBox ID="chkSelect" runat="server" onclick="Check_Click(this)" />
                    </ItemTemplate>
                </asp:TemplateField>

                <asp:BoundField HeaderText="Q_ID" DataField="Q_Multiple_ID" />

                <asp:BoundField HeaderText="The Question" DataField="Multiple_Question" />




            </Columns>

        </asp:GridView>

the c#

protected void GetSelectedRecords(object sender, EventArgs e) {

    string selected = "";
    foreach (GridViewRow row in GridView3.Rows)

        {

            CheckBox chk = (CheckBox)row.FindControl("chkSelect");


        // get the selected AutoId and cells text
        if (chk.Checked)
            {

            string QID = GridView3.DataKeys[row.DataItemIndex].Values["Q_Multiple_ID"].ToString();
            selected += QID;
            test.Text = selected;


        }
    }

    test.Text = selected;

}