How to ignore joining objects in LINQ Select statement to pull record-CodePudding

I am working on LINQ script/lambda to pull data from objects. There is a joining table/class to connect A and B table/ object.

I have managed to pull the record but it is in the following form

List<IEnumerable<ValidationRule>>

where I want to ignore joining object and simply get List<ValidationRule>?

public static List<ValidationRule> GetValidations(string fieldName, Dictionary<string, DataMappingPolicy> dataMappingPolicies)
{
    List<ValidationRule> validationRules = new List<ValidationRule>();

    var policyValidations = dataMappingPolicies.Where(_ => _.Key == fieldName).Select(_ => _.Value.PolicyValidationRules.Select(_ => _.ValidationRule)).ToList();

    return validationRules;
}

DataMappingPolicy

public class DataMappingPolicy
{
    public DataMappingPolicy()
    {
        this.PolicyValidationRules = new HashSet<PolicyValidationRule>();
    }

    public Guid DataMappingPolicyId { get; set; }

    public ICollection<PolicyValidationRule> PolicyValidationRules { get; set; }

}

PolicyValidationRule

public class PolicyValidationRule
{
    public Guid PolicyValidationRuleId { get; set; }
    public Guid DataMappingPolicyId { get; set; }
    public DataMappingPolicy DataMappingPolicy { get; set; }
    public Guid ValidationRuleId { get; set; } 
    public ValidationRule ValidationRule { get; set; }
}

CodePudding user response：

Flatten the list from PolicyValidationRules to get all ValidationRule via .SelectMany().

var policyValidations = dataMappingPolicies
    .Where(_ => _.Key == fieldName)
    .SelectMany(_ => _.Value.PolicyValidationRules)
    .Select(_ => _.ValidationRule)
    .ToList();

CodePudding user response：

I have an Idea on how you can fix your problem.

public static List<ValidationRule> GetValidations(string fieldName, Dictionary<string, DataMappingPolicy> dataMappingPolicies)
    {
        List<ValidationRule> validationRules = new List<ValidationRule>();

        var policyValidations = dataMappingPolicies.Where(_ => _.Key == fieldName).Select(_ => _.Value.PolicyValidationRules.Select(_ => _.ValidationRule));

        foreach(var item in policiValidations)
        {
           validationRules.Add(item);
        }

        return validationRules;
    }

First remove the the ToList() from your code.

Then if policyValidations is of type IEnumerable<ValidationRule> than you should be able to iterate through the values with a foreach statement and add each of them to the list you are trying to return.

CodePudding user response：

You can use SelectMany which flattens queries that return lists of lists.

var policyValidations = dataMappingPolicies.Where(_ => _.Key == fieldName)
                         .Select(_ => _.Value)
                         .SelectMany(_ => _.PolicyValidationRules)
                         .Select(_ => _.ValidationRule))
                         .ToList();