CODEWITHSUNDEEP
c#.netnullnullif
AXMIM
AXMIM

Reputation: 2472

Is there an equivalent of SQL NULLIF function in c#?

Is there an equivalent of SQL NULLIF function built-in within c#?

Example of what it could look like :

double? result
double denominator = 0;
double Numerator = 100;
result = Numerator / NullIf(denominator, 0);
result = Numerator / denominator.NullIf(0);
result = Numerator / Object.NullIf(denominator, 0);

Upvotes: 12

Views: 9185

Answers (5)

JM123
JM123

Reputation: 187

Why do we assume this extension method is able to know what is null in our context.

Its the responsibility of the context that calls it. Therefore is a mistake of saying only one value will be considered null as all the response in this thread impliy.

public static T? NullIf<T>(this T value, Func<T,bool> isConsideredNull) 
{
        if(value == null)
        {
           return null;
        }
        return isConsideredNull(value) ? (T?)null : value;
}

We would use it the following way

string test = "NULL";

test.NullIf((x)=> x.Equals("NULL"));
test.NullIf((x)=> x == "NULL");
test.NullIf((x)=> x.Equals("NULL",StringComparison.InvariantCultureIgnoreCase));

Upvotes: 0

BorisSh
BorisSh

Reputation: 571

Accepted answer give me:

Operator '==' cannot be applied to operands of type 'T' and 'T'

My working example of NULLIF:

public static T? NullIf<T>(T left, T right) where T : struct
{
    return EqualityComparer<T>.Default.Equals(left, right) ? (T?)null : left;
}

Upvotes: 7

Rowland Shaw
Rowland Shaw

Reputation: 38130

No, there is no language feature for this at present.

You can easily get the same result, either with a ternary if:

result = Numerator / (denominator == 0 ? (double?)null : denomiantor);

Or even wrapping it as a generic function, so something like:

Nullable<T> NullIf<T>(T left, T right)
{
    return left == right ? (T?)null : left;
}

which could then be called like:

result = Numerator / NullIf(denominator, 0);

Upvotes: 9

juharr
juharr

Reputation: 32276

No but you could create one.

public static Nullable<T> NullIf<T>(T first, T second) where T : struct
{
    if(first == second)
        return new Nullable<T>();
    return new Nullable<T>(first);
}

Upvotes: 4

vittore
vittore

Reputation: 17579

There is no. but you can use ternary operator for compact way of writing it:

double? result
double denominator = 0;
double Numerator = 100;
result = denominator == 0 ? (double?)null : Numerator / denominator;

However there is equivalent of IFNULL:

result = x ?? 0;

equivalent of:

result = x.HasValue? x.Value : 0;

Upvotes: 1

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