How can I bypass the validation while click on anchor tag of menu.

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C#

ASP.NET

I have set require field validator for few fields of insert mode formview(AddVenue.aspx). Its working fine on click event of my Insert Button.But When I am navigate through few menus/submenu(which contains click event) of my menubar(AddVenue.aspx), all validation is getting trigger. please help me how I can avoid validation on click event of menu and Submenu.

What I have tried:

AddVenue.aspx.cs

public void click_Vendor1(object sender, EventArgs e)
    {
        Vendor1.CausesValidation = false;
        Session["VendorCategory"] = "Photographers";
        Response.Redirect("SearchVendor.aspx");
        
    }
    public void click_Vendor2(object sender, EventArgs e)
    {
        Vendor2.CausesValidation = false;
        Session["VendorCategory"] = "Makeup Artists";
        Response.Redirect("SearchVendor.aspx");
        
    }
    public void click_Vendor3(object sender, EventArgs e)
    {
        Vendor3.CausesValidation = false;
        Session["VendorCategory"] = "Mehendi Artists";
        Response.Redirect("SearchVendor.aspx");

    }
    public void click_Vendor4(object sender, EventArgs e)
    {
        Vendor4.CausesValidation = false;
        Session["VendorCategory"] = "Decorators";
        Response.Redirect("SearchVendor.aspx");
    }
    public void click_Vendor5(object sender, EventArgs e)
    {
        
        Vendor5.CausesValidation = false;
        Session["VendorCategory"] = null;
        Response.Redirect("SearchVendor.aspx");
    }

AddVenue.aspx

<ul>
                                                                       <li><a href='#' runat="server" id="Vendor1"   onserverclick="click_Vendor1">Photographers</a></li>
                                                                       <li><a href='#' runat="server" id="Vendor2" onserverclick="click_Vendor2">Makeup Artists</a></li>
                                                                       <li><a href='#' runat="server" id="Vendor3" onserverclick="click_Vendor3">Mehendi Artists</a></li>
                                                                       <li><a href='#' runat="server" id="Vendor4" onserverclick="click_Vendor4">Wedding Lawns</a></li>
                                                                       <li><a href='#' runat="server" id="Vendor5" onserverclick="click_Vendor5">All Wedding Vendors</a></li>
                                                           </ul>