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What is a NullReferenceException, and how do I fix it?
...ess members (such as methods) through a null reference. The simplest case:
string foo = null;
foo.ToUpper();
This will throw a NullReferenceException at the second line because you can't call the instance method ToUpper() on a string reference pointing to null.
Debugging
How do you find the source ...
How to enumerate an enum with String type?
...n, you may specify the conformance directly in the declaration:
enum Suit: String, CaseIterable { case spades = "♠"; case hearts = "♥"; case diamonds = "♦"; case clubs = "♣" }
Then the following code will print all possible values:
Suit.allCases.forEach {
print($0.rawValue)
}
Compatib...
Efficiently updating database using SQLAlchemy ORM
... the fields manually:
from sqlalchemy import Column, ForeignKey, Integer, String, Date, DateTime, text, create_engine
from sqlalchemy.exc import IntegrityError
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy.orm.attributes import Instr...
How to get the list of all printers in computer
...
Try this:
foreach (string printer in System.Drawing.Printing.PrinterSettings.InstalledPrinters)
{
MessageBox.Show(printer);
}
share
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imp...
Why is string concatenation faster than array join?
Today, I read this thread about the speed of string concatenation.
9 Answers
9
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How to use enums in C++
...es themselves don't have members. What you wrote is the equivalent to std::string.clear. std::string is a type, so you can't use . on it. You use . on an instance of a class.
Unfortunately, enums are magical and so the analogy stops there. Because with a class, you can do std::string::clear to g...
Which characters make a URL invalid?
...
Here's a regex that will determine if the entire string contains only the characters above: /^[!#$&-;=?-[]_a-z~]+$/
– Leif Wickland
Oct 7 '11 at 17:01
...
How to create a jQuery plugin with methods?
...the wrapping function) and check for an entry if the parameter passed is a string, reverting to a default method ("init" here) if the parameter is an object (or null).
Then you can call the methods like so...
$('div').tooltip(); // calls the init method
$('div').tooltip({ // calls the init method...
How do I print the type of a variable in Rust?
... This is intended for diagnostic use. The exact contents and format of the string are not specified, other than being a best-effort description of the type.
If you want your type representation to stay the same between compiler versions, you should use a trait, like in the phicr's answer.
...
How to disable margin-collapsing?
...) entail using a 1px border or 1px padding. I find this unacceptable: the extraneous pixel complicates calculations for no good reason. Is there a more reasonable way to disable this margin-collapsing?
...