for (int i = 1; i < txtFiles.Length-1; i++)
                {                 
                    ds_files.InsertParameters[0].DefaultValue = txtFiles[i]; // массив с именами файлов
                    ds_files.Insert();
                }

<asp:SqlDataSource ID="ds_files" runat="server" 
        ConnectionString="<%$ ConnectionStrings:aut_ConnectionString %>"
            ProviderName="<%$ ConnectionStrings:aut_ConnectionString.ProviderName %>" 
            SelectCommand="SELECT template_files FROM Template_File" 
            InsertCommand="insert into Template_File (template_files) values (?)"
            UpdateCommand="update Template_File set template_files=? ">
            <InsertParameters>
                <asp:Parameter Name="template_files" Type="String" />
                </InsertParameters>
            <UpdateParameters>
                <asp:Parameter Name="template_files" Type="String" />
                </UpdateParameters>
        </asp:SqlDataSource>