Question

在常规SQL中，我可以编写类似

的查询

select * from geocodes where NAME='somename' and STATE='somestate'

但是在LINQ中，我不知道该怎么做。我想为使用LINQ的以下单个查询编写一些组合查询：

if (!String.IsNullOrEmpty(searchString))
        {
            switch (searchBy)
            {
                case "Name":
                    geocodes = geocodes.Where(s => s.NAME.Contains(searchString));
                    break;
                case "Site":
                    geocodes = geocodes.Where(s => s.CFN_SITE.Contains(searchString));
                    break;
                case "Address":
                    geocodes = geocodes.Where(s => s.STREET1.Contains(searchString));
                    break;
                case "City":
                    geocodes = geocodes.Where(s => s.CITY.Contains(searchString));
                    break;
                case "State":
                    geocodes = geocodes.Where(s => s.STATE_CODE.Contains(searchString));
                    break;
                case "Acct":
                    geocodes = geocodes.Where(s => s.AccountNumber.Contains(searchString));
                    break;
            }

        }

Answer 1

使用&&逻辑AND运算符：

geoCodes = geoCodes.Where(s => s.Name.Contains(someName) && s.State.Contains(someState));

Answer 2

如果geocodes是IQueryable<>，则可以利用创建可查询对象所附带的延迟执行。您的代码可能看起来像这样：

if(searchByName) //Some boolean value to indicate you are searching the name
{
    geocodes = geocodes.Where(s => s.NAME.Contains(searchString));
}

if(searchBySite)
{
    geocodes = geocodes.Where(s => s.CFN_SITE.Contains(searchString));
}

if(searchByAddress)
{
    geocodes = geocodes.Where(s => s.STREET1.Contains(searchString));
}

//etc...

您的查询实际上不会发送到数据库，因为您纯粹是在构建它。仅当您通过枚举结果（通过调用ToList()或仅对其进行循环）来实现数据时，实体框架才会构建所需的SQL

将“ WHERE”查询与LINQ结合

2 个答案: