pass a null as a one param argument

I have a method that accepts params as a parameter to check if a property has invalid value or not. If the property has an invalid value, it throws an exception

private void ShouldNotEqual<T>(Expression<Func<Ticket, T>> outExpr, params object[] notValidPropertyValue)

The usage is:

ShouldNotEqual(student => student.Name, "jack", string.Empty);
ShouldNotEqual(student => student.Address, string.Empty, null);

The problem with this implementation is when I want to check a property against null, the parameter notValidPropertyValue is set as null, not an array with one element whose value is equal to null.

// I need to use it in this way
ShouldNotEqual(student => student.Phone, null); // Throws NullReferenceException for notValidPropertyValue

How can I fix it?

Solution 1:

Explicitly pass an object[]:

ShouldNotEqual(student => student.Phone, new object[] { null });

Or add an overload to prevent this happening:

private void ShouldNotEqual<T>(
    Expression<Func<Ticket, T>> outExpr,
    object notValidPropertyValue)
{
    ShouldNotEqual(outExpr, new object[] { notValidPropertyValue });
}

This will take precedence when a single object, or null is passed.

Solution 2:

Are you sure you want null in the array and not just an empty array?

If you want null, use

var array = new object[] { null };

to create an array containing one value, null.

Then call ShouldNotEqual with the array, e.g.

ShouldNotEqual(student => student.Phone, array);

Or just inline it:

ShouldNotEqual(student => student.Phone, new object[] { null });

If you want an empty array, then just use

ShouldNotEqual(student => student.Phone, new object[0]);