Why doesn't instantiating an object automatically instantiate its properties?

Question

I have the following classes:

public class CustomerResult
{
    public string CompanyStatus { get; set; }
    public OverallResult Result { get; set; }
}

public class OverallResult
{
    public string StatusDescription { get; set; }
    public int StatusCode { get; set; }
    public string CustomerId { get; set; }        
}

I instantiate:

var apiResult = new CustomerResult();

Why does the following return a null reference? Surely OverallResult is instantiated when I create CustomerResult()?

apiResult.Result.CustomerId = "12345";

Answer 1

Because you didn't create an instance for Result. Reference types have null values by default and OverallResult is a class, hence a reference type.

You can do it in constructor.

public class CustomerResult
{
    public string CompanyStatus { get; set; }
    public OverallResult Result { get; set; }
    public CustomerResult(){
        Result = new OverallResult();
    }
}

---

if your C# version heigher than 6.0 there is a simpler way Auto-Property Initializers

C# 6 enables you to assign an initial value for the storage used by an auto-property in the auto-property declaration:

public class CustomerResult
{
    public string CompanyStatus { get; set; }
    public OverallResult Result { get; set; } = new OverallResult();
}