從lambda表達式中排除null或空字符串值

在我的GetAll函數應用程序中，我有一個名為（ CustomerModel ）的參數。我用它來對查詢進行一些過濾，我使用規範模式來避免使用if-else ：

    public async Task<List<CustomerModel>> GetAllAsync(CustomerModel customer, Order order = Order.Ascending, int pageIndex = 1, int pageSize = int.MaxValue)
    {
        var skip = (pageIndex - 1) * pageSize;

        var filter = new CustomerNameSpecification(customer)
            .And(new CustomerNoSpecification(customer))
            .And(new CustomerCompanySpecification(customer))
            .And(new CustomerPhoneSpecification(customer))
            .And(new CustomerEmailSpecification(customer))
            .And(new CustomerAddressSpecification(customer))
            .Take(pageSize)
            .Skip(skip);

        var orderSpecification = new CustomerOrderSpecification(order);

        return await _customerRepository.GetAllAsync(filter, orderSpecification);
    }

例如，規範對象之一（ CustomerNameSpecification ）：

public class CustomerNameSpecification : Specification<Customer>
{
    public CustomerModel Customer { get; set; }

    public CustomerNameSpecification(CustomerModel customerModel)
    {
        Customer = customerModel;
    }

    public override Expression<Func<Customer, bool>> AsExpression()
    {
        return customerFiler =>
            customerFiler.Name.Contains(Customer.Name);
    }
 }

UPDATE

並在規範模式中操作：

public class AndSpecification<T> : Specification<T> 
    where T : class
{
    private readonly ISpecification<T> _left;
    private readonly ISpecification<T> _right;

    public AndSpecification(ISpecification<T> left, ISpecification<T> right)
    {
        _left = left;
        _right = right;
    }

    public override Expression<Func<T, bool>> AsExpression()
    {
        var leftExpression = _left.AsExpression();
        var rightExpression = _right.AsExpression();

        var parameter = leftExpression.Parameters.Single();
        var body = Expression.AndAlso(leftExpression.Body, SpecificationParameterRebinder.ReplaceParameter(rightExpression.Body, parameter));

        return Expression.Lambda<Func<T, bool>>(body, parameter);
    }
  }
}

這些鏈在最後創建一個lambda表達式，存儲庫使用它來過濾查詢。

當CustomerModel每個字段都有值時，此解決方案可以正常工作，但即使一個屬性具有null值或空值，它也不起作用。

如何修復此問題並排除lambda表達式，其中我有一個空值或空字符串值？