选择列表中的Bootstrap Modal弹出窗口是否已关闭？

Question

我正在模态弹出窗口上创建2下拉列表，从数据库中获取，但是当我选择任何选项时，模态弹出窗口已关闭。我该如何解决？帮助我解决这个问题！我也曾在模式弹出式按钮的单击按钮上写过data-backdrop="static" data-keyboard="false"，但没有用。

<div class="modal fade" id="myModal" role="dialog">

        <div class="modal-dialog">

          <!-- Modal content-->
          <div class="modal-content">
            <div class="modal-header">
              <button type="button" class="close" data-dismiss="modal">&times;</button>
              <h4 class="modal-title">Your Orderline Item</h4>
            </div>
              <div class="modal-body">
                  <div class="col-lg-12 col-sm-12 col-md-12 col-xs-12">
                      <div class="form-group">
                          <asp:Label ID="lblBrandnames" runat="server" Text="Brand Name"></asp:Label>
                          <div style="margin-left: 5%">
                              <asp:DropDownList ID="drpListBrands" runat="server" OnSelectedIndexChanged="brandname_changed" AutoPostBack="true"></asp:DropDownList>
                          </div>
                      </div>
                      <div class="form-group">
                          <asp:Label ID="lblProductnames" runat="server" Text="Product Name"></asp:Label>
                          <div style="margin-left: 5%">
                              <asp:DropDownList ID="drpListProduct" runat="server" AutoPostBack="true" ></asp:DropDownList>
                              <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
                              <cc1:AutoCompleteExtender ID="AutoCompleteExtender1" runat="server"></cc1:AutoCompleteExtender>
                          </div>
                      </div>
                      <div class="form-group">
                          <asp:Label ID="lblquantity" runat="server" Text="Quantity"></asp:Label>
                          <div style="margin-left: 5%">
                              <asp:TextBox ID="txtQuantities" runat="server"></asp:TextBox>
                          </div>
                      </div>
                  </div>
              </div>
            <div class="modal-footer">
              <button type="button" style="background-color:orange" data-dismiss="modal">Close</button>

            </div>
          </div>
        </div>
      </div>