Using MVC3 WebGrid - Column does not exist error

I am getting this error - System.InvalidOperationException: Column "UserID" does not exist.

This is my View Model.

public class UserVM
{
    public int UserID;
    public string Name;
}

This is my action method in the controller.

public ActionResult TestGrid()
{
    List<UserVM> rows = new List<UserVM>();
    rows.Add(new UserVM { UserID = 100, Name = "Abc" });
    rows.Add(new UserVM { UserID = 101, Name = "Def" });
    rows.Add(new UserVM { UserID = 102, Name = "Ghi" });
    return View("TestGrid", rows.AsEnumerable());
}

This is my view.

@model IEnumerable<Module.ViewModels.UserVM>
@{
    var grid = new WebGrid(Model);
}

<div>
@grid.GetHtml(
    columns: grid.Columns(
        grid.Column("UserID", header: "User ID"),
        grid.Column("Name", header: "Name")
    )
)
</div>

That's it. Any idea why I am getting the error?

Your UserVM class is using fields instead of properties. Will not work with webgrid.
Here's your class with properties:

public class UserVM
{
    public int UserID { get; set; }
    public string Name { get; set; }
}