Question 87884 in ASP.NET Question posted in
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Null checking for if then in C# – Asp.net

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

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5

Answers


  1. 0

    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))
{
}
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  2. 0

    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)
{
    /// 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

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  3. 0

    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.

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  4. 0

    One liner using System.Linq.

    if (result.Data.FirstOrDefault()?.AdditionalDate != null)
{
 
}
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  5. 0

    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

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