Linq查询性能很慢

Question

I have 700 records that have different columns with type string and I want to select all records using this code:

public virtual object GetAll()
{
    var AllList = unitOfWork.Repository<STUser>().GetAll().ToList();

    return (from STUser in AllList
            select new
            {
                STUser.ID,
                FullName = STUser.HRPerson.LastName,
                STUser.USR,
                STUser.Active,
                STUser.TryCount,
                STUser.Description           
            }).OrderByDescending(i => i.ID).ToList();
}

However, unitl Fill "var AllList" is good but when Linq query execution is very slow. I removed FullName = STUser.HRPerson.LastName, line and it was executed very fast. Join clause slowed it down.

I ran SQL profiler for every row in the List and it looks like it executes the Query 700 times. Query is

exec sp_executesql N'SELECT 
[Extent1].[ID] AS [ID], 
[Extent1].[FirstName] AS [FirstName], 
[Extent1].[LastName] AS [LastName], 
[Extent1].[EnFullName] AS [EnFullName], 
[Extent1].[FatherName] AS [FatherName], 
[Extent1].[GenderID] AS [GenderID], 
[Extent1].[NationalCode] AS [NationalCode], 
[Extent1].[IdentityNumber] AS [IdentityNumber], 
[Extent1].[BirthCityID] AS [BirthCityID], 
[Extent1].[BirthDate] AS [BirthDate], 
[Extent1].[VeteranID] AS [VeteranID], 
[Extent1].[PersonPic] AS [PersonPic], 
[Extent1].[Active] AS [Active], 
[Extent1].[Description] AS [Description], 
[Extent1].[DateTimes] AS [DateTimes]
FROM [dbo].[HRPerson] AS [Extent1]
WHERE [Extent1].[ID] = @EntityKeyValue1',N'@EntityKeyValue1 int',@EntityKeyValue1=1502

Please help me.

Answer 1

i use IQueryable in repo and add Include(u => u.HRPerson) its ok

var AllList = unitOfWork.Repository<STUser>().GetAll().Include(u => u.HRPerson).ToList();

thankyou @HansKesting for your help

Answer 2

Just a thought I would like to share: (I'm not familiar with that platform)

What about this:

public virtual IEnumerable<YourDataObject> GetAll()
{
    var result = from STUser in unitOfWork.Repository<STUser>().GetAll() // << what is GetAll()??
                 orderby STUser.ID
                 select new YourDataObject // <-- you should create a data holder class for it
                 {
                    STUser.ID,
                    FullName = STUser.HRPerson.LastName,
                    STUser.USR,
                    STUser.Active,
                    STUser.TryCount,
                    STUser.Description
                 });

    return result;
}

By doing the ordering before the creation of the data holder class, you might use an optimalization on the database side.

Answer 3

You could try using.AsNoTracking() on your query.

From the Microsoft docs -

No tracking queries are useful when the results are used in a read-only scenario. They're quicker to execute because there's no need to set up the change tracking information. If you don't need to update the entities retrieved from the database, then a no-tracking query should be used. You can swap an individual query to be no-tracking.

More here - https://docs.microsoft.com/en-us/ef/core/querying/tracking