Null checking for if then in C#-CodePudding

I am checking two conditions which is following in C#:

 if (result.Data.Count > 0)
 {
     if(result.Data[0].AdditionalData != null)
      {
         // To Do
      }
  }

My confusion is there is any better way to check these in a single if condition?

I am trying to use Null-Condition operator, but did not work it. Null-Conditional operator in MSDN

CodePudding user response：

Like written also by @Hans Killian try to use the extensions already there for IEnumerables In your case I think .ElementAtOrDefault(0) (or if you always want to use index 0 just use .FirstOrDefault()) is the best fit for you here.

if (result?.Data != null && result.Data.Any())
{
    /// Expecting 'AdditionalData' is `string`
    if (!string.IsNullOrEmpty(result.Data.ElementAtOrDefault(0)?.AdditionalData))
    {
        Console.WriteLine("Null check working...");
    }
    else
    {
        Console.WriteLine("AdditionalData is null or empty!");
    }
}
else
{
    Console.WriteLine("No data!");
}

Full working example can be found here

CodePudding user response：

One liner using System.Linq.

if (result.Data.FirstOrDefault()?.AdditionalDate != null)
{
 
}

CodePudding user response：

I think the best way to have clean and good code is to use FluentValidation. Please note the following code snippet:

  public class RegisterValidator : AbstractValidator<RegisterDTO>
{
    public RegisterValidator()
    {
        RuleFor(a => a.PhoneNumber).NotNull().WithMessage(Utility.GetEnumTitlePersian(enmErrorMessage.InValidMobileNumber));
        RuleFor(a => a.PhoneNumber).NotEmpty().WithMessage(Utility.GetEnumTitlePersian(enmErrorMessage.InValidMobileNumber));
        RuleFor(a => a.PhoneNumber).MinimumLength(11).WithMessage(Utility.GetEnumTitlePersian(enmErrorMessage.InValidMobileNumber));
        RuleFor(a => a.PhoneNumber).MaximumLength(11).WithMessage(Utility.GetEnumTitlePersian(enmErrorMessage.InValidMobileNumber));
    }

}

The above code is an example of validating a model to check null, empty and etc. and this code must check validation in business logic:

var validator = new RegisterValidator();
var validatorResult = await validator.ValidateAsync(register);

if (!validatorResult.IsValid)
    return BadRequest("", validatorResult.Errors[0].ToString());

It is very simple to use and very clean. You can even perform multiple checks and get results through the error list This link is the site address of FluentValidation

CodePudding user response：

You forgot to check the value is empty or not. Empty or null is differences value.

CodePudding user response：

Null conditional can work along with Any, and short-circuiting the next check

if (result?.Data?.Any() && result.Data[0]?.AdditionalData != null)
{
    // to do
}

Explanation of each of the steps

result?

Is result not null?

Data?

if so, is Data not null?

Any()

if so, does Data have any items?

Data[0]?

if so, is the first item not null? (the reason I use index here is because you may want to check the nth item, so FirstOrDefault may be too restrictive)

AdditionalData != null

if so, is Additional data not null?

Of course, if any of these checks are unnecessary or superfluous you can remove the specific check from the chain (remove ? in the case of null-conditional). Here the checks are all laid out clearly in one line so it's simple to modify the chain of logic.

CodePudding user response：

You can create extension method on IEnumerable and use it

    public static bool HasValue<T>(this IEnumerable<T> source, int index)
    {
        if (source == null)
            return false;

        return source.Count() > index && source.ElementAt(index) != null;
    }

// usage
if(result.Data.HasValue(0))
{
}