我正在创建一个概念证明,它使用Lambda / LINQ来进行动态的和orderby.以下代码适用于where表达式,但我无法弄清楚如何通过表达式创建顺序.对于这个例子,如果可能,我想保持简单;我宁愿不编写修改表达式树的代码.
void Main()
{
DateTime productSince = DateTime.UtcNow.Subtract(new TimeSpan(1,30,0));
Expression<Func<Products,bool>> filter = d => d.CreatedDate > productSince && d.Price < 100 ;
List<Products> products = GetProducts(filter,Products);
Console.WriteLine(products);
}
private static List<Products> GetProducts(Expression<Func<Products,bool>> filter,Table<Products> Products)
{
var products = Products.Where(filter);
return products.ToList();
}
我想要的是类似于以下内容,但无法弄清楚通过表达式创建顺序的代码.
void Main()
{
DateTime productSince = DateTime.UtcNow.Subtract(new TimeSpan(1,bool>> filter = d => d.CreatedDate > productSince && d.Price < 100 ;
Expression<Func<Products,????>> orderBy = d => ??????;
List<Products> products = GetProducts(filter,orderBy,Expression<Func<Products,???>> orderBy,Table<Products> Products)
{
var products = Products.Where(filter).OrderBy(orderBy);
return products.ToList();
}
如果你想知道,我使用LinqPad这个概念证明.
解决方法
private static List<Products> GetProducts<TOrderBy>(Expression<Func<Products,TOrderBy>> orderBy,Table<Products> Products)
{
var products = Products.Where(filter).OrderBy(orderBy);
return products.ToList();
}
如果你看到OrderBy扩展方法,它接受一个表达式< Func< T,TOrderBy>>因为表达式可能导致任何类型的依赖
.OrderBy(x => x.ID) // <T,int> .OrderBy(x => x.Name) // <T,string>
因此,您的包装方法需要能够接受通用类型.
