Getting NullReferenceException in Code

Question

What is wrong with this code?

public partial class MainForm : Form
 {
        private Dictionary<String , PropertyInfo[]> types;  
        public MainForm()
        {
            //OpenAccountStruct is in the scope
            types.Add("OpenAccount", new OpenAccountStruct().GetType().GetProperties());
        }
}

Why am I getting NullReferenceException?

Put types = new Dictionary(); on the first line of your method. — Mike Chaliy, Sep 22 '11 at 07:18
Basic debugging would have taught you that `types` is the null reference here, and so your question has very little, if anything, to do with Reflection. — Damien_The_Unbeliever, Sep 22 '11 at 07:19
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, May 15 '14 at 19:38

score 4 · Answer 1 · answered Sep 22 '11 at 07:17

4

You didn't make an instance of types (your Dictionary).

try

types = new Dictionary<String , PropertyInfo[]>();

answered Sep 22 '11 at 07:17

gsharp

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Might wanna mention that `types` is the dictionary. – Aviad P. Sep 22 '11 at 07:18

score 1 · Answer 2 · answered Sep 22 '11 at 07:18

1

The types variable is not initialized. Use types = new Dictionary<String , PropertyInfo[]>();

answered Sep 22 '11 at 07:18

Johann Blais

9,249
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score 0 · Accepted Answer · answered Sep 22 '11 at 07:19

0

 private Dictionary<String , PropertyInfo[]> types = 
                        new Dictionary<String , PropertyInfo[]>();

answered Sep 22 '11 at 07:19

Rami Alshareef

6,787
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score 0 · Answer 4 · answered Sep 22 '11 at 07:20

Obviously, your types field is not initialized,

 public partial class MainForm : Form
 {
        private Dictionary<String , PropertyInfo[]> types = new Dictionary<String , PropertyInfo[]>();
        public MainForm()
        {
            //OpenAccountStruct is in the scope
            types.Add("OpenAccount", new OpenAccountStruct().GetType().GetProperties());
        }
}

Getting NullReferenceException in Code

4 Answers4