在LINQ表达式有条件的经营者造成异常的NHibernate [英] Conditional operator in Linq Expression causes NHibernate exception

问题描述

我想在ASP.NET MVC 2应用程序中实现搜索功能。我创建基于用户输入的条件表达式：

I'm trying to implement search functionality in an ASP.NET MVC 2 application. I create an expression based on criteria entered by the user:

public ViewResult FindCustomer( string forename, string familyname, DateTime? dob)
  {
  Expression<Func<Customer, bool>> searchCriteria = p => (
                                                            forename.IsNullOrEmpty() ? true : p.Forename == forename
                                                            && familyname.IsNullOrEmpty() ? true : p.FamilyNames.Any(n => n.Name == familyname)
                                                            && dob.HasValue ? true : p.DOB == dob
                                                            ); 

然后把它传递给方法在存储库

which then gets passed to a method in the repository

IQueryable<Customer> customers = CustomerRepository.FilterBy(searchCriteria);

现在的问题是，当我运行此我得到下面的异常

The problem is when I run this I get the following exception

System.InvalidCastException: Unable to cast object of type 'NHibernate.Hql.Ast.HqlCast' to type 'NHibernate.Hql.Ast.HqlBooleanExpression'

据的这个的问题是在表达式中使用条件运算符。

According to this the problem is the use of the conditional operator in the expression.

所以，我想我必须创建表达一些其他的方式，但我不知道该怎么做。我是很新，这样的Linq任何帮助将欣然接受！

So I suppose I have to create the Expression some other way but I'm not sure how to do that. I'm pretty new to Linq so any help would be gratefully accepted!

推荐答案

什么动态创建查询？像这样的：

What about dynamically create your query? Like this:

var customers = CustomerRepository.AllEntities();

if (!forename.IsNullOrEmpty())
    customers = customers.Where(p => p.Forename == forename);
if (!familyname.IsNullOrEmpty())
    customers = customers.Where(p => p.FamilyNames.Any(n => n.Name==familyname));
if (dob.HasValue)
    customers = customers.Where(p => p.DOB == dob);

我不知道，如果这个工程，但我认为这可能是更有效的。

I don't know if this works but I think this could be more efficient.

这篇关于在LINQ表达式有条件的经营者造成异常的NHibernate的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！