Validate DropDown if CheckBox is checked in ASP.Net using jQuery

Here I have created sample that will help you out.

HTML

<div>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <script type="text/javascript">
        $(document).ready(function () {
            $('[id*=btnSave]').click(function () {
                var IsValid = true;
                $('[id*=myGridview] tr:not(:has(th))').each(function () {
                    var chk = $(this).find('[id*=CheckBox1]');
                    if (chk.is(':checked')) {
                        if ($.trim($(('[id*=ddlRole]'), $(chk).closest('tr')).val()) == "") {
                            $(('[id*=ddlRole]'), $(chk).closest('tr')).focus();
                            alert('Please select a Project Role from the dropdown box.');
                            IsValid = false;
                        }
                    }
                });
                return IsValid;
            });
        });
    </script>
    <asp:GridView ID="myGridview" runat="server" AutoGenerateColumns="false">
        <Columns>
            <asp:TemplateField HeaderText="ID" Visible="true">
                <ItemTemplate>
                    <asp:Label ID="lblID" runat="server" Text='<%# Eval("PRJ_ID")%>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Title" Visible="true">
                <ItemTemplate>
                    <asp:Label ID="lblPrjTit" runat="server" Text='<%# Eval("PRJ_TITLE")%>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Project Role">
                <ItemTemplate>
                    <asp:DropDownList ID="ddlRole" CssClass="form-control" runat="server">
                        <asp:ListItem Text="" />
                        <asp:ListItem Text="Role1" />
                        <asp:ListItem Text="Role2" />
                    </asp:DropDownList>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Check">
                <ItemTemplate>
                    <asp:CheckBox ID="CheckBox1" runat="server" AutoPostBack="true" />
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>
    <br />
    <br />
    <asp:Button ID="btnSave" Text="Save" runat="server" />
</div>

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[]
                { 
                    new DataColumn("PRJ_ID") ,
                    new DataColumn("PRJ_TITLE") 
                }
        );
        dt.Rows.Add("1", "Title1");
        dt.Rows.Add("2", "Title2");
        myGridview.DataSource = dt;
        myGridview.DataBind();
    }
}

Screenshot

this is how i solved

<script type="text/javascript">
      function validateDDL() {
          //debugger;

      var flag = true;
      var gridView = document.getElementById('<%= gvSearch.ClientID %>');

      for (var i = 1; i < gridView.rows.length; i++) {
        var inputs = gridView.rows[i].getElementsByTagName('input');
        var dropdowns = gridView.rows[i].getElementsByTagName('Select');

       if (inputs != null && inputs.length >= 1 && inputs[0] != null && dropdowns != null && dropdowns.length >= 1 && dropdowns[0] != null) {

            if (dropdowns[0].type == "select-one" && inputs[0].type == "checkbox") {
              var ddlSelectedItem = dropdowns[0].value;

             // if (inputs[0].checked && (ddlSelectedItem == "Select" || txtval == null)) {
                if (inputs[0].checked && ddlSelectedItem == "Select" ) {

                flag = false;
                break;
              }
              else {
                flag = true;

              }
            }
          }
        }

      if (!flag) {
        alert('your message alert here');

    }
    return flag;
  }

  </script>