Question

我想在过滤属性具有值（非空）时使用where条件构建查询。如果使用多个过滤器，则它们必须是AND组合。

当where属性值不为null时，如何组合/添加每个谓词以使最终查询准备好进行过滤？

IQueryable<Customer> filter = null;

Expression<Func<Customer, bool>> predicatetest1 = res => res.test1 == request.test1;
Expression<Func<Customer, bool>> predicatetest2 = res => res.test2 == request.test2;
Expression<Func<Customer, bool>> predicatetest3 = res => res.test3 == request.test3;

if (request.test1 != null)
{
     // add the above predicate to the filter
}

if (request.test2 != null)
{
    // add the above predicate to the filter
}

if (request.test3 != null)
{
   // add the above predicate to the filter
}

Answer 1

IQueryable<Customer> filter = Context.Customers;

if (request.test1 != null)
{
  filter = filter.Where(predicatetest1);
}

if (request.test2 != null)
{
  filter = filter.Where(predicatetest2);
}

if (request.test3 != null)
{
  filter = filter.Where(predicatetest3);
}

var customers = filter.ToList();

当所有3个属性都不为空时

，以下内容将是等效的

Context.Customers.Where(predicatetest1).Where(predicatetest2).Where(predicatetest3).ToList();

从多个谓词构建IQueryable

1 个答案: