Question

public ActionResult Index()
{
    Queries q1 = new Queries();
    return View(q1);
}

public ActionResult Index(string id)
{
    Queries q1 = new Queries(id);
    return View(q1);
}

public ActionResult Select(string id)
{
    return RedirectToAction("Index",id);
}

what is wrong…

It says:
The current request for action ‘Index’ on controller type ‘CompanyController’ is ambiguous between the following action methods:
System.Web.Mvc.ActionResult Index() on type LookUpForm.Controllers.CompanyController
System.Web.Mvc.ActionResult Index(System.String) on type LookUpForm.Controllers.CompanyController

Since the Action Index one doesnot have parameters and other have a string parameter, I think it must be valid.

Answer 1

You cannot have 2 actions on the same controller with the same name even if they take different parameters. The only way to disambiguate them is to use a different HTTP verb:

public ActionResult Index()
{
    Queries q1 = new Queries();
    return View(q1);
}

[HttpPost]
public ActionResult Index(string id)
{
    Queries q1 = new Queries(id);
    return View(q1);
}

or if both actions need to be accessible with the GET verb you will have to either find a different name or write a custom action selector.