asp.net-mvc LINQ Distinct()
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LINQ Distinct()
提问by Pinu
I am working on getting the results of this sql query in LINQ
我正在努力在 LINQ 中获取此 sql 查询的结果
SELECT DISTINCT(Type)
FROM Product
WHERE categoryID = @catID
this is my repository query:
这是我的存储库查询：
public IQueryable<ProdInfo> GetProdInfo()
{
var data = from u in db.Prod
select new ProdInfo
{
PID = u.PID,
CatID = u.CatID,
LastChanged = u.LastChanged,
ChangedBy = u.ChangedBy,
Type = u.Type,
};
return data;
}
filter:
筛选：
public static IQueryable<ProdInfo> GetDistinctProdType(this IQueryable<ProdInfo> qry,int CatID)
{
return from p in qry
where p.CatID.Equals(CatID)
select p;
}
I need the filter to return the distinct prod type? How can i do this?
我需要过滤器来返回不同的 prod 类型吗？我怎样才能做到这一点？
回答by Jon Skeet
Simply like this:
就像这样：
public static IQueryable<ProdType> GetDistinctProdType(
this IQueryable<ProdInfo> query,
int categoryId)
{
return (from p in query
where p.CatID == categoryId
select p.Type).Distinct();
}
Note that I've changed the return type - it should match whatever the type of ProdInfo.Typeis.
请注意，我已经更改了返回类型 - 它应该匹配任何类型ProdInfo.Type。
You may find it more readable to use the extension methods for the whole query if the query expression itself is reasonably simple:
如果查询表达式本身相当简单，您可能会发现对整个查询使用扩展方法更具可读性：
public static IQueryable<ProdType> GetDistinctProdType(
this IQueryable<ProdInfo> query,
int categoryId)
{
return query.Where(p => p.CatID == categoryId)
.Select(p => p.Type)
.Distinct();
}
回答by msarchet
return (from p in qry
where p.CatId.Equals(CatID)
select p.Type).Distinct();
This matches what your provided SQL Query should be doing.
这与您提供的 SQL 查询应该执行的操作相匹配。
