Error: LINQ to Entities does not recognize the method 'System.String ToString(System.Object)' method occurs while string conversion

I have an entity framework's EDMX generated class.

public partial class Contact : EntityBase
{
    public Contact()
    {
    }

    public string FirstName { get; set; }
    public string MiddleName { get; set; }
    public string LastName { get; set; }
    public string NickName { get; set; }
    public Nullable<System.DateTime> DOB { get; set; }
}

I've a LINQ expression for searching a text against all above properties.

Expression<Func<Contact, bool>> cntExpression = p => p.LastName.ToLower().Trim().Contains(searchedText) ||
                p.FirstName.ToLower().Trim().Contains(searchedText) ||
                p.MiddleName.ToLower().Trim().Contains(searchedText) ||
                p.NickName.ToLower().Trim().Contains(searchedText) ||
                (p.DOB.HasValue && p.DOB.Value.ToShortDateString().ToLower().Trim().Contains(searchedText));

'searchedText' is a variable containing the text value which has to be matched.

I now used business logic class's method to filter records using the above LINQ expression.

IQueryable<Contact> qryContact = _cntMgr.GetFiltered(cntExpression);

Till here the code gets executed, but it throws error while looping through Contact records existing in the above IQueryable result.

foreach (var contact in qryContact)
            {
                if (contact!=null)
                {
                    // Some code executes here..
                }
            }

The error I get is this:

 LINQ to Entities does not recognize the method 'System.String ToString(System.Object)' method, and this method cannot be translated into a store expression.

I already know that System.String ToString is not supported in Linq to Entities, but I need a solution or a workaround for this issue.

Please help me in getting it fixed.

Thanks in advance.