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Difference between OperationCanceledException and TaskCanceledException?
What is the difference between OperationCanceledException and TaskCanceledException ? If I am using .NET 4.5 and using the async / await keywords, which one should I be looking to catch?
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Why use sprintf function in PHP?
..., specify number format (hex, decimal, octal), number of decimals, padding and more. Google for printf and you'll find plenty of examples. The wikipedia article on printf should get you started.
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Find kth smallest element in a binary search tree in Optimum way
...(log n) in the worst case on a balanced BST, or O(log n) on average for a random BST.
A BST requires O(n) storage, and it takes another O(n) to store the information about the number of elements. All BST operations take O(depth of node) time, and it takes O(depth of node) extra time to maintain the...
How do I write outputs to the Log in Android?
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Look into android.util.Log. It lets you write to the log with various log levels, and you can specify different tags to group the output.
For example
Log.w("myApp", "no network");
will output a warning with the tag myApp and the ...
Method call if not null in C#
...ke();
or:
obj?.SomeMethod();
The ?. is the null-propagating operator, and will cause the .Invoke() to be short-circuited when the operand is null. The operand is only accessed once, so there is no risk of the "value changes between check and invoke" problem.
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Prior to C# 6, no: there is no...
Difference between two lists
...Using Except is exactly the right way to go. If your type overrides Equals and GetHashCode, or you're only interested in reference type equality (i.e. two references are only "equal" if they refer to the exact same object), you can just use:
var list3 = list1.Except(list2).ToList();
If you need t...
printf() formatting for hex
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The # part gives you a 0x in the output string. The 0 and the x count against your "8" characters listed in the 08 part. You need to ask for 10 characters if you want it to be the same.
int i = 7;
printf("%#010x\n", i); // gives 0x00000007
printf("0x%08x\n", i); // gives 0x0...
Cloning a MySQL database on the same MySql instance
...s a bit dodgy.
Integrated from various good other answers
Both mysqldump and mysql commands accept options for setting connection details (and much more), like:
mysqldump -u <user name> --password=<pwd> <original db> | mysql -u <user name> -p <new db>
Also, if the ...
jQuery Data vs Attr?
What is the difference in usage between $.data and $.attr when using data-someAttribute ?
3 Answers
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Find rows that have the same value on a column in MySQL
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This query will give you a list of email addresses and how many times they're used, with the most used addresses first.
SELECT email,
count(*) AS c
FROM TABLE
GROUP BY email
HAVING c > 1
ORDER BY c DESC
If you want the full rows:
select * from table where email ...