linq中基于参数值的倍数 [英] multiple where in linq based on parameters value

问题描述

我想在linq中有多个where子句，但是其中只有一个应该执行，我正在尝试如下操作:

I want to have multiple where clauses in linq but out of them only one should execute, i was trying something like this:

public JsonResult GetPost(int? id, int? tagid, DateTime? date)
{
    var ret = from data in db.Posts.Include(x => x.Tags)
                 .Include(x => x.Neighbourhood)
                 .Where((x => x.NeighbourhoodId == id) || (y => y.PostedDate == date) || third condition).ToList()

但是在y后面加点之后，我无法在第二和第三条件那里放becoz，我看不到任何选择.

but i was unable to put second and third condition there becoz after putting dot after y, i cant see any options.

现在，在这三个参数中，只有一个参数将具有值，而另外两个参数将具有null，因此，它仅应检查具有值的参数.

Now, out of these three, only one parameter would have value and other two would have null so, it should checks for parameter only with value.

我应该这样写查询吗，这是正确的方法吗?

should i write query like this, is it correct way:

if (id != null)
{
//whole query here
}
else if (tagid != null)
{
//whole query here
}
else (date != null)
{
//whole query here
}

这是执行此操作的最佳方法，还是可能的其他方法.任何建议都要提前很多.

Is it the best way to do this or something else is possible. many many thnks in advance for any suggestion.

推荐答案

像这样吗?

            var ret = from data in db.Posts.Include(x => x.Tags)
             .Include(x => x.Neighbourhood)
             .Where(x => x.NeighbourhoodId == (id ?? x.NeighbourhoodId) &&
                         x.<condition>  == (tagid ?? x.<condition>) &&
                         x.PostedDate == (date ?? x.PostedDate).ToList();

或者像这样:

            var ret = from data in db.Posts.Include(x => x.Tags)
             .Include(x => x.Neighbourhood)
             .Where(x => id.HasValue ? x.NeighbourhoodId == id :
                            tagid.HasValue ? x.<condition> == tagid :                             
                                x.PostedDate == date).ToList();

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