Huma Ali Huma Ali - 1 year ago 71
C# Question

Lambda Expression for Finding properties

I want to retreive

property from
is equal to

public class PromotionCatalogResponseRootObject
public PromotionCatalogResponse PromotionCatalog { get; set; }

public class Promotion
public string PromotionId { get; set; }
public string LineOfBusiness { get; set; }
public string PromotionName { get; set; }

public class PromotionCatalogResponse
public List<Promotion> Promotion { get; set; }

I started off like this but I know I'm doing it wrong. Please guide

string myId = "7596";
string lineOfBusiness = dataPromotionCatalog.PromotionCatalog
.Promotion.Find(p => p.LineOfBusiness);

Answer Source

What you are missing is the the Find method is expecting to receive a predicate with a bool return value but you are returning a string, the LineOfBusiness property.

First filter the items you want and then select the desired property. In addition, I'd go with the Where instead of the Find. (Find() vs. Where().FirstOrDefault())

var result = dataPromotionCatalog.PromotionCatalog.Promotion
                                 .Where(i => i.PromotionId == myId)
                                 .Select(i => i.LineOfBusiness);

or in query syntax

var result = (from item in dataPromotionCatalog.PromotionCatalog.Promotion
              where item.PromotionId == myId
              select item.LineOfBusiness);

If you are expecting/want to have one item then use FirstOrDefault:

var result = dataPromotionCatalog.PromotionCatalog.Promotion
                 .FirstOrDefault(i => i.PromotionId == myId)?.LineOfBusiness;
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