Question

我有这个LINQ：

    private static IQueryable<Contract> getValidContracts(DbContext context, DateTime date,int clientId)
    {
        return (from contract in context.Set<Contract>()
                where contract.ValidityDate >= date
                where contract.ClientId == clientId
                select contract);
    }

LINQ中的

我给了这一行：

 where contract.ClientId == clientId

我希望只有当 clientId 变量不等于零时，此行才会包含在where子句中。

任何想法我怎样才能使它优雅？

Answer 1

只需在其中添加0的检查

where ((contract.ClientId == clientId && clientId != 0) || clientId == 0)

Answer 2

由于客户端ID是外部变量，您可以在LINQ外部检查它：

if(clientId==0)
{
   return (from contract in context.Set<Contract>()
                where contract.ValidityDate >= date
                select contract);
}
else
{
 return (from contract in context.Set<Contract>()
                where contract.ValidityDate >= date
                where contract.ClientId == clientId
                select contract);
}

Answer 3

对于动态查询，最好使用流畅的语法。在这种特殊情况下，您可以使用类似这样的内容

private static IQueryable<Contract> getValidContracts(DbContext context, DateTime date, int clientId)
{
    var query = context.Set<Contract>().Where(contract => contract.ValidityDate >= date);
    if (clientId != 0)
        query = query.Where(contract => contract.ClientId == clientId);
    return query; 
}

Answer 4

您可以将条件修改为：

where ((clientId!=0)?(contract.ClientId == clientId):true)

LINQ with conditional where子句

4 个答案: