This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 5 years ago.
first time posting on here and a bit of a noob in c#. Basically I'm creating a linkedlist and initializing it to null at the beginning of my class. When I'm ready to use it, I check to make sure that it's not equal to the string passed by the method. I immediately get a NullReferenceException, and i'm supposed to be comparing it to null. Any fixes?
private DoubleLinkedListCell<DoubleLinkedListCell<GamePiece>> _columns = null;
public void FindColumn(string columnId)
{
bool right = true;
while (_columns.Id != columnId)
{
if (_columns.Next == null)
{
right = false;
}
if (right)
{
Columns = Columns.Next;
}
else
{
Columns = Columns.Prev;
}
}
}
You will get null reference if u try to access any property or member of _columns List (ex _columns.Id,_columns.Next etc..) so initialize it in constructor or direct when u declare field
Related
This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 1 year ago.
script 1
[SerializeField] public int staminaLeft;
[SerializeField] public int maxStamina;
void Start()
{
maxStamina = 100;
staminaLeft = maxStamina;
}
second script
public PlayerStamina playerStamina;
private void Update()
{
if (playerStamina.staminaLeft <= 0)
{
}
else if (playerStamina.maxStamina > 0 && !fillImage.enabled)
{
}
}
It says Object reference not set to an instance of that object but I am quite sure that playerStamina.staminaLeft has a value that isn't null
It says that your object variable playerStamina is null.
I don't see in your code that you checked that this object is not null so that it might be that this object is null.
You might initialize it with the new keyword and also you might verify in your method that playerStamina is not null to avoid unhandled exceptions.
This question already has answers here:
Check if list is empty in C#
(8 answers)
Closed 3 years ago.
This is my Code:
public int PostCanal(List<int> listchannel) {
if (listchannel == null || listchannel.Contains(0))
{
listchannel.Add(1);
}
This list has values coming from a checkbox menu. So, if the user uncheck all the options I want to still using "1" as default value.
On this case, the listchannel List<int> is arriving with [0] value. However the if condition is skipped.
Any idea? Also tried .Equals Method.
You could use Any Or Count to check if the list is empty or not, like the following code :
if(listchannel == null || !listchannel.Any())
{
}
//Or
if(listchannel == null || listchannel.Count == 0)
{
}
I hope you find this helpful.
This question already has answers here:
C# difference between == and Equals()
(20 answers)
Are string.Equals() and == operator really same? [duplicate]
(8 answers)
Closed 5 years ago.
I'm writing a simple contains function which accepts a value and checks if it exists in the linked list. Returns a bool. However, when temp.Data is the same as data, as checked through debugging, it still proceeds to enter the while statement and cycle through the list, as if they are not equal. I have found a solution, by using toString() on all values. So I have to compare temp.Data.ToString() and data.ToString(). Then it works...I am new to C#, I haven't used the Object keyword much. I'm wondering if it's something to do with that? So my function works with my quick fix but I'm trying to understand why...thanks!
public bool Contains(Object data)
{
Node temp = head;
while((temp.Data != data) && (temp.Next != null))
{
temp = temp.Next;
}
//Rest of code
This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 8 years ago.
In my model I have this particular property to add two different model values and show it in my index page.
public decimal Amount
{
get { return Products.Price * Qty; }
}
When I go to my create page and try to create another sale after I hit submit I get a yellow screen of death with the following:
Object reference not set to an instance of an object.
System.NullReferenceException: Object reference not set to an instance of an object.
It points to this part of my model get { return Products.Price * Qty; }
I'm not really interested in storing anything from here, and I don't even use the Amount property in my create page. Is there a way to tell it to ignore on submit?
How about this?
public decimal Amount
{
get
{
if (Products == null) { return 0; }
return Products.Price * Qty;
}
}
This question already has answers here:
Easier way of writing null or empty?
(7 answers)
Closed 9 years ago.
Is there any way to check for string either it is null or blank("") in c#?
Currently I have to check two conditions first for null and other for blank value
if(val == "" || val == null)
{
return true;
}
You can use String.IsNullOrEmpty() method which checks for string references that are null or have no data:
if(String.IsNullOrEmpty(val))
{
return true;
}
There is also a method String.IsNullOrWhitespace() which indicates whether a specified string is null, empty, or consists only of white-space characters.
if(String.IsNullOrWhitespace(val))
{
return true;
}
The above is a shortcut for the following code:
if(String.IsNullOrEmpty(val) || val.Trim().Length == 0)
{
return true;
}
You can use String.IsNullOrEmpty method.
Indicates whether the specified string is null or an empty string.
if(String.IsNullOrEmpty(val))
{
return true;
}
There is easiest and simple way.
if (string.IsNullOrEmpty("Val")) //This condition comparing both NULL and EMPTY also
{
}
.Net has provided default function for this purpose you should use like this.
if (string.IsNullOrEmpty("any string"))
{
}
You can use String.IsNullOrEMpty.