使用 LINQ 按孙子过滤列表

Question

I need to filter a list by the DamageCodeName field in the DamageCode class.

public partial class DamageCategory
{
    public string DamageCategoryId { get; set; }
    public string CategoryName { get; set; }
}

public partial class DamageGroup
{
    public string DamageGroupId { get; set; }
    public string DamageCategoryId { get; set; }
    public string GroupName { get; set; }
}

public partial class DamageCode
{
    public string DamageCodeId { get; set; }
    public string DamageGroupId { get; set; }
    public string DamageCodeName { get; set; }
}

I pull the records using EF CORE 5 into a list:

private List<DamageCategory> _DamageCodeList { get; set; } = new();

_DamageCodeList = _contextDB.DamageCategories
                            .Include(i => i.DamageGroups)
                            .ThenInclude(d => d.DamageCodes).AsSingleQuery().ToListAsync();

Now I need to filter this list by the DamageCode.DamageCodeName property.

private string _SearchText { get; set; } = "Bubble";
private List<DamageCategory> _CategoryList { get; set; } = new();

_CategoryList = _DamageCodeList.Where(g => g.DamageGroups.SelectMany(c => c.DamageCodes
                               .Where(w => w.DamageCodeName.ToLower().Contains(_SearchText.ToLower()))).Any()).ToList();

The code above only filters for the DamageCategory. It brings back all the records for the DamageGroup and all the records for the DamageCodes.

I need the linq query result to produce a list like the one below (Filtered by "Bubble") and bring back only the DamageCategory, DamageGroup, and DamageCodes filtered by DamageCode.DamageCodeName.Contains("Bubble"):

Here is the SQL that produces the result above that I need:

SELECT 
    CT.[DamageCategoryID],
    CT.[CategoryName],
    DG.[DamageGroupID],
    DG.[DamageCategoryID],
    DG.[GroupName],
    DC.[DamageCodeID],
    DC.[DamageGroupID],
    DC.[DamageCodeName]
  FROM 
    [dbo].[DamageCategory] AS CT
    INNER JOIN [dbo].[DamageGroup] AS DG ON CT.[DamageCategoryID] = DG.[DamageCategoryID]
    INNER JOIN [dbo].[DamageCode] AS DC ON DG.[DamageGroupID] = DC.[DamageGroupID]
  WHERE 
    DC.[DamageCodeName] LIKE '%Bubble%'

Answer 1

This is where query syntax shines.

from dc in _contextDB.DamageCategories
from dg in dc.DamageGroups
from dc in dg.DamageCodes
where dc.DamageCodeName.Contains("Bubble")
select new
{
    dc.DamageCategoryID,
    dc.CategoryName,
    dg.DamageGroupID,
    dg.DamageCategoryID,
    dg.GroupName,
    dc.DamageCodeID,
    dc.DamageGroupID,
    dc.DamageCodeName
}

The query shape from... from is the query syntax equivalent of SelectMany .

You use ToLower in your code. That may not be necessary. The query is translated into SQL and if the database field has a case-insensitive collation you don't need ToLower .