How to convert string to nullable int LINQ

Question

I saw a lot of questions like this but seems I cant find anything to relate one to another and find solution for mine. I am using MVC 4 application where I have a dropdownlist with some values inside.

I am using viewbag to populate it.

ViewBag.Roles = new SelectList(db.Roles, "RoleId", "RoleName");

In the view my dropdown looks like this.

@Html.DropDownList("selectedRole", ViewBag.Roles as SelectList, String.Empty)

The string selectedRole is getting the RoleId value from the view.

After this I am doing some LINQ to the database with selectedRole which says that I cannot convert string to Int inside my LINQ which I really want so I can return better results.

     public ActionResult SearchResults(string selectedRole, string selectedCourse, string SearchParam)
        {
            var members = (from m in db.Members
                           select m);

            if (!String.IsNullOrEmpty(selectedRole))
            {
                members = (from m in db.Members
                           where m.UserRole == Int32.Parse(selectedRole)
                           select m);


            }
        //some more if's here...
        return View(members.ToList());
}

So the question is how to convert this selectedRole to Integer. Are there any rules to follow when converting in LINQ?

PS: I tried also Convert.ToInt32(selectedRole) which returns same error.

Saying "I receive an error" isn't enough. There are hundred of possible errors. You should write the error in the question. — xanatos
– xanatos, Commented Apr 26, 2015 at 18:16

xanatos · Accepted Answer · 2015-04-26 18:11:27Z

3

In this case the question is irrelevant...

if (!String.IsNullOrEmpty(selectedRole))
{
    int selectedRole2 = Int32.Parse(selectedRole);

    members = (from m in db.Members
               where m.UserRole == selectedRole2
               select m);

You don't do it in linq, you do it outside.

In general, you aren't using only Linq, you are using Linq-to-Sql or Linq-to-Entities, because Members is a table. Sadly at least Linq-to-Entities doesn't have any cast method. You can obtain something similar by using a user defined function, but it is a little complex. Linq-to-Sql instead should support Convert.ToInt32 (see https://msdn.microsoft.com/en-us/library/vstudio/bb882655.aspx)

answered Apr 26, 2015 at 18:11

xanatos

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1 Comment

vLr Over a year ago

Very simple solution, feeling dumb right now. I got on the same query the same error using Convert.ToInt32 so I doubt it supports any conversion at all.

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