assign a name to your checkbox:
<input name="gender" type="checkbox" id="@checkBoxId" class="chkclass" value="@names.Value" />
Then accept a string array of with parameter name gender
[HttpPost]
public ActionResult HandleFormSubmit(string[] gender,
MembershipFormViewModel model)
{
//model not valid, do not save, but return current umbraco page
if (ModelState.IsValid == false)
{
return CurrentUmbracoPage();
}
string test = "Gender: " + model.Gender + Environment.NewLine; //getting null here
return RedirectToCurrentUmbracoPage();
}