Registering a custom filter
Name Surname Marital status Age Employed
Joe Crosswave Married 36 False
Merry Lisel Widowed 46
Henry Crux Single 34 True
Cody Jurut 54 False
Simon Scranton Single 39
Leena Laurent Divorced 24 False
Ode Cosmides Married 58 True
Diandra Mizner Single 25 False
Pete Cassel Married 27 False
Nicky Tremblay Married 36 True
Startup 

MvcGrid.Filters.Register(typeof(Int32), "contains", typeof(NumberContainsFilter))
Filter 

public class NumberContainsFilter : BaseGridFilter
{
    public override Expression Apply(Expression expression)
    {
        if (Values.Count == 0 || Values.Any(String.IsNullOrEmpty))
            return null;

        return base.Apply(expression);
    }

    protected override Expression Apply(Expression expression, String value)
    {
        Expression valueExpression = Expression.Constant(value.ToUpper());
        MethodInfo toStringMethod = typeof(Int32).GetMethod("ToString", new Type[0]);
        MethodInfo containsMethod = typeof(String).GetMethod("Contains", new[] { typeof(String) });

        Expression toString = Expression.Call(expression, toStringMethod);

        return Expression.Call(toString, containsMethod, valueExpression);
    }
}
Javascript 

var ExtendedNumberFilter = (function (base) {
    MvcGridExtends(ExtendedNumberFilter, base);

    function ExtendedNumberFilter(column) {
        base.call(this, column);

        this.methods.unshift('contains');
    }

    return ExtendedNumberFilter;
})(MvcGridNumberFilter);

new MvcGrid(document.querySelector('.mvc-grid'), {
    filters: {
        'number': ExtendedNumberFilter
    }
});

MvcGrid.prototype.lang.number.contains = 'Contains';