对象引用不是设置为对象的实例，而是吗？

Question

I must be missing something here, but I've got an instance of my submission object called up, in scope, and when I try to use it in another line, I throw this error about not setting the reference to an instance. What gives?

protected void Page_Load(object sender, EventArgs e)
{

    string x = Request.QueryString["SubmissionId"];

    SubmissionService ss = new SubmissionService();
    Submission sub = ss.getSubmissionByID(x);

if (sub.Status1.Equals(0))
    {
        PanelComment.Visible = false;

    }
    else

Answer 1

These could be null:

ss 
sub
sub.Status1
x

Put a breakpoint, and debug...

Answer 2

您的提交对象“ sub”上的Status1属性可能为null ...

Answer 3

Given the code that you supplied, there can be three causes:

1. the "Status1" property is null, this would generate a NullReferenceException.
2. PanelComment is null
3. sub is null

Answer 4

Given the code, the following properties could be null:

• Submission sub (If there is no submission with the ID = x)
• sub.Status1
• List item

PanelComment

Just change your code by the following:

Submission sub = String.IsNullOrEmpty(x) ? null : ss.getSubmissionByID(x);

if (sub!= null && sub.Status1 == 0){
...

It should fix most of the null references.