将值赋给属性时出现空错误(Null error when assigning value to property)

 尝试创建一个自定义对象，允许我在记录中拾取错误。 
 
public class gridIntegerField
{
    private int value;
    private bool isValid;
    private string message;



    public int Value
    {
        get { return this.value; }
        set { this.value = value; }
    }
    public bool IsValid
    {
        get { return isValid; }
        set { isValid = value; }
    }
    public string Message
    {
        get { return message; }
        set { message = value; }
    }


}

public class gridRecord    
{
    private gridIntegerField printRun;

    public gridIntegerField PrintRun
    {
      get { return printRun; }
      set { printRun = value; }
    }

}
 
 当创建对象并尝试设置值时，我得到以下错误... 
 
 XML-Console.exe中发生了未处理的“System.NullReferenceException”类型异常 
 
 创建对象的代码...... 
 
gridRecord spr = new gridRecord();
spr.PrintRun.Value = 200;
spr.PrintRun.IsValid = true;
spr.PrintRun.Message = "No Errors";

Console.WriteLine(spr.PrintRun.Value.ToString());
Console.WriteLine(spr.PrintRun.IsValid.ToString());
Console.WriteLine(spr.PrintRun.Message.ToString());
Console.ReadKey();
 
 错误发生在这行代码中 
 
spr.PrintRun.Value = 200;

Trying to create a custom object that will allow me to pickup errors in the records. 
 
public class gridIntegerField
{
    private int value;
    private bool isValid;
    private string message;



    public int Value
    {
        get { return this.value; }
        set { this.value = value; }
    }
    public bool IsValid
    {
        get { return isValid; }
        set { isValid = value; }
    }
    public string Message
    {
        get { return message; }
        set { message = value; }
    }


}

public class gridRecord    
{
    private gridIntegerField printRun;

    public gridIntegerField PrintRun
    {
      get { return printRun; }
      set { printRun = value; }
    }

}
 
when creating object and trying to set the values i get the folowing error...
 
An unhandled exception of type 'System.NullReferenceException' occurred in XML- Console.exe
 
Code for creating object...
 
gridRecord spr = new gridRecord();
spr.PrintRun.Value = 200;
spr.PrintRun.IsValid = true;
spr.PrintRun.Message = "No Errors";

Console.WriteLine(spr.PrintRun.Value.ToString());
Console.WriteLine(spr.PrintRun.IsValid.ToString());
Console.WriteLine(spr.PrintRun.Message.ToString());
Console.ReadKey();
 
the error happens at this line of code 
 
spr.PrintRun.Value = 200;

原文：https://stackoverflow.com/questions/33119791