過濾 LINQ 中的嵌套對象

Question

我在 LINQ 中有以下查詢，以返回帶有策略風險列表的策略對象，並在策略風險中返回其事務移動列表。

corePolicy = _db.Policies
    .OrderByDescending(p => p.BatchId)
    .Include(policy => policy.PolicyRisks.Select(policyRisks =>
        policyRisks.TransactionMovements))
    .Include(policy => policy.PolicyRisks.Select(policyRisks =>
        policyRisks.PolicyRiskClaims.Select(prc =>
            prc.TransactionMovements)))
    .AsNoTracking()
    .First(p =>
        p.PolicyReference == policyFromStaging.PolicyReference &&
        p.PolicySourceSystemId == policyFromStaging.PolicySourceSystemId);

我如何將.Where()子句應用於交易動作，比如TransactionReference == 'ABC'

下面是我的數據模型

[Table("business.Policy")]
public class Policy
{
    [Required, StringLength(50)]
    public string PolicyReference { get; set; }

    public int PolicySourceSystemId { get; set; }
    public System PolicySourceSystem { get; set; }
}

[Table("business.PolicyRisk")]
public class PolicyRisk
{
    public ICollection<TransactionMovement> TransactionMovements { get; set; }
}

[Table("business.TransactionMovement")]
public class TransactionMovements
{
    public string TransactionReference { get; set; }
}

Answer 1

不可能在 Include 中使用 Where 語句。 你可以有任何類似下面的東西：

corePolicy = _db.Policies
.OrderByDescending(p => p.BatchId)
.Include(policy => policy.PolicyRisks.Select(policyRisks =>
    policyRisks.TransactionMovements))
.Include(policy => policy.PolicyRisks.Select(policyRisks =>
    policyRisks.PolicyRiskClaims.Select(prc =>
        prc.TransactionMovements)))
.AsNoTracking()
.Where(p => p.PolicyRisks.Any(pr => pr.PolicyRiskClaims.Any(prc => prc.TransactionMovements.Any(tm => tm.TransactionReference == 'ABC'))))
.First(p =>
    p.PolicyReference == policyFromStaging.PolicyReference &&
    p.PolicySourceSystemId == policyFromStaging.PolicySourceSystemId);

如果任何交易引用是 ABC（在其子集合上），這將包括策略。 因此，您再次必須在 c# 端有一個循環機制來獲取具有此 TransactionReference 的策略。

如果您想避免循環，那么我建議您從其他端含義編寫 linq，從 TransactionMovement 開始，然后返回 Policy。

您可以使用此處提到的某些第三方庫在 Include 過濾器中使用 WHERE 子句。