This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 8 years ago.
When im trying to set checkbox.checked, i got null refedence exception. I dont know why, it looks like that checkbox isnt initialized.
There is my code
public UpdateProduct(DataGridViewRow row,Form1 form)
{
this.row = row;
this.form = form;
product = row.DataBoundItem as object;
visibilityCheckBox.Checked = true;
InitializeComponent();
}
Exception is firing in line visibilityCheckBox.Checked = true;
Please can anybody help me with this issue ? Thanks much !
I guess you didn't call InitializeComponent before, and since you are trying to set it before the call to InitializeComponent, visibilityCheckBox will be null.
Call InitializeComponent first or write another method that does only update the created UI elements.
Related
This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 3 months ago.
I am getting this error:
NullReferenceException: Object reference not set to an instance of an object Obstacle.OnTriggerEnter2D (UnityEngine.Collider2D collision) (at Assets/Scripts/Obstacle.cs:22)
There is no problem in the code. Where am I making a mistake?
[[enter image description here](https://i.stack.imgur.com/sSDkt.png)](https://i.stack.imgur.com/PRHdO.png)
Please help.
This is an issue caused by a small typo in the form of a lowercase ‘s’ instead of an uppercase ‘S’.
Because the Unity Engine was looking for Start and couldn’t find it, your “start” code never ran. Because of that, your Player was never assigned to, and had a “null reference”. And that’s why when you tried to read the tag, for a reference that was null, you got the error.
Your code should be:
private void Start ()
{
..
}
Note the exact case for Start and all C# commands.
This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 1 year ago.
When I am inputting wrong username and password this error shows
this is my code
RegLog reuser = res.ResultAs<RegLog>(); //database result <-- Error Occurs here.
any solution? I already tried to declare it as var but error still persist.
Thank you.
It is because for some reason (probably wrong username and password), the variable res is null.
Try to check a null reference before using res.
Example: if(res == null) { //do something }
This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 2 years ago.
This code is basically using the code from https://gist.github.com/runewake2/b4b7bf73485222f7c5a0fe0c91dd1322strong text
I have already assigned the variable but still got this error. Can anybody tell me how? I watched this guy tutorial and he did it with this code so there shouldn't be a problem I guess.
The problem is that you don't initialize the property private Material material; When you create object like that you create a reference that points to null. In your code you are trying to modify this object but since it's not initialized it's null. The solution is to initialize it in the constructor like so:
public FlowLines()
{
this.material = new Material();
}
This question already has answers here:
Why is there a default instance of every form in VB.Net but not in C#?
(2 answers)
Objects implicitly instantiated in vb.net?
(2 answers)
Closed 7 years ago.
Recently I've picked an old project in VB.NET and I keep finding things like this that annoy me:
Dim answer as String
answer = Form_Input_Text.Lbl_Answer.Text
Apparently, in VB.NET it is allowed to access stuff which should belong to an instance of a Form as if it is something static. In C# one would need to write this:
string answer = null;
using (Form_Input_Text my_form = new Form_Input_Text())
{
//stuff
answer = my_form.Lbl_Answer.Text;
}
The first bit of code is compiled with no errors, but sometimes I get NullReferenceException as expected.
How do I enforce this behaviour on VB.NET?
This question already has answers here:
Clearing a drop down list in C#
(2 answers)
Closed 8 years ago.
I am trying with this line of code :
comboxBox.items = null;
it's not working, i have an error.
Anyone can give me a hand ? Thanks.
You can try like this :
comboBox.items.Clear ();
or like this :
comboBox.dataSource = null;
depend if its datasource
if you want to show an empty selection , try this :
comboBox.selectedIndex = -1;
Hope this will help :)
comboBox.Items.Clear();
Should do the trick.
Items is a read-only property of the combo box, so you can't assign to it.