How to solve Object reference not set to an instance of an object.? [duplicate]

Question

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• What is a NullReferenceException, and how do I fix it? 31 answers

In my asp.net program.I set one protected list.And i add a value in list.But it shows Object reference not set to an instance of an object error

protected List<string> list;
protected void Page_Load(object sender, EventArgs e)
{
     list.Add("hai");
}

How to solve this error?

Answer 1

You need to initialize the list first:

protected List<string> list = new List<string>();

Answer 2

I think you just need;

List<string> list = new List<string>();
list.Add("hai");

There is a difference between

List<string> list; 

and

List<string> list = new List<string>();

When you didn't use new keyword in this case, your list didn't initialized. And when you try to add it hai, obviously you get an error.