在代码中获取NullReferenceException

Question

此代码有什么问题？

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

为什么我会收到NullReferenceException？

Answer 1

您没有制作types（您的词典）的实例。

试

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

Answer 2

types变量未初始化。 使用types = new Dictionary<String , PropertyInfo[]>();

Answer 3

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

Answer 4

显然，您的类型字段未初始化，

 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());
        }
}