检查对象是否为空

Question

I am coding a MVC 5 internet application, and I have a question in regards to checking if an object is null or not, before setting some values in the object.

Here is some example code:

public async Task TestFunction(TestObject obj)
{
    obj.name = "Test Name";
    repository.Insert(obj);
}

Should the check to see if the object is null be done before the function call every time? Is there any need at all to check if the object is null within the function call?

Thanks in advance.

Answer 1

It depends on the purpose of the function, in your function's case it looks like you will be using it to insert the object into a repository therefore passing a null object into a repository should throw an exception and not just silently fail.

You should check for null and throw an ArgumentException if the parameter is null.

public async Task TestFunction(TestObject obj)
{
    if(obj == null) {
        throw new ArgumentException("obj cannot be null");
    }

    obj.name = "Test Name";
    repository.Insert(obj);
}

However there are cases where you could have a function that can accept a null object possibly returning a default value if you do pass it in.

Just don't write code like this:

public async Task TestFunction(TestObject obj)
{
    if(obj != null) {//if null don't do anything 
        obj.name = "Test Name";
        repository.Insert(obj);
    }
}

This method will do nothing and if the developer calling it didn't realise that the object passed was null then it will fail silently without letting the developer know what happened.