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

Question

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?

Almost all cases of `NullReferenceException` are the same. Please see "[What is a NullReferenceException in .NET?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net)" for some hints. — John Saunders, Nov 22 '13 at 08:28

score 97 · Accepted Answer · answered Nov 22 '13 at 08:15

97

You need to initialize the list first:

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

answered Nov 22 '13 at 08:15

Tinsa

Soner Gönül · Answer 2 · 2013-11-22T08:22:50.257

31

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.

edited Nov 22 '13 at 08:22

answered Nov 22 '13 at 08:16

Soner Gönül

2 Answers2