Question

嘿，我有以下疑问，即

    public int GetDefaultCurrencyForOrganization(string organizationId)
    {
        return (from a in _dataContext.allocations
                where a.organizationId.Equals(organizationId)
                select a.currencyId).SingleOrDefault();
    }

对于很多公司来说，这可能不会返回任何内容，而这是我想要设置值4来返回。只是想知道如何将其添加到上面？

Answer 1

我认为你正在寻找这样的东西：

public int GetDefaultCurrencyForOrganization(string organizationId)
{
    return (from a in _dataContext.allocations
            where a.organizationId.Equals(organizationId)
            select (int?)a.currencyId).SingleOrDefault() ?? 4;
}

你也可以这样做：

public int GetDefaultCurrencyForOrganization(string organizationId)
{
    var alloc = _dataContext.allocations
        .SingleOrDefault(a => a.organizationId.Equals(organizationId));
    return alloc != null ? alloc.currencyId : 4;
}

Answer 2

尝试使用DefaultIfEmpty（4）而不是SingleOrDefault来指定值：

public int GetDefaultCurrencyForOrganization(string organizationId)
{
    return (from a in _dataContext.allocations
            where a.organizationId.Equals(organizationId)
            select a.currencyId).DefaultIfEmpty(4).Single();
}

http://msdn.microsoft.com/en-us/library/bb355419.aspx

Linq检查值是否存在，否则设置默认值

2 个答案: