如何在C#中检查int数组对象是否为空？

Question

I have an array of int grades[5]. I have a loop that checks the objects of the array one by one to see if they're empty. I used:

if (grades[i] != null)

I get an error message that an int object is never "null" and therefor this expression always returns "true." If not "null," how do I check to see if a specific object in the array is empty?

Thanx a lot for the help!

Answer 1

I think you should check for the default value of 0 like so.

if (grades[i] != 0)

However, if 0 is a valid value in your use case and you are expecting to store null (ie grade not set ) then you should declare the array as of type nullable int . Like so.

int?[] grades

Then you can check for null value in individual items like so.

if (grades[i].HasValue )
{  
    // mean grades[i] is not null and has some int value inside it
}

Answer 2

int is not a nullable type. If you want to be able to check an empty int, you must use a nullable int : int? .

Answer 3

int is a non-nullable type, instead of being null it will have its default value of 0 . If you want to have an array of int that allows for nulls you can make use of a nullable int. int?

You could use it this way

int?[] grades = new int?[5];
if (grades[i].HasValue) //The way to check for != null

Then to retrieve the value it does not work like a traditional int .

int gradeValue = grades[i].Value;

Answer 4

int should be nullable according to implement this.

Nullabele int array is creation can be done using this

int?[] grades = new int?[5];

You can check whether there is value using

grades[i].HasValue

Answer 5

I would consider making a validator class. Code above should be work on nullable types too.

public class ArrayObjectValidator<T>
{
public ArrayObjectValidator(T[] array)
{
    this.array = array;
}

private T[] array { get; set; }

public bool ValidateIndex(int index)
{
    bool result = false;

    if (array != null && array.Length > 0)
    {
        result = CheckItemAt(index);
    }

    return result;
}

private bool CheckItemAt(int index)
{
    return index >= 0 && index < array.Length && NullControl(index);
}

private bool NullControl(int index)
{
    return array[index] != null && array[index] is T;
}
}

you can use it as below;

int[] integerArray = new int[10]={1,2,3,4,5,6,7,8,9,0};
ArrayObjectValidator<int> intArrayObjValidator = new ArrayObjectValidator<int>(integerArray);
bool isItemAtIndexFiveNullOrEmpty = integerArray.ValidateIndex(5);