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Entity Framework code first unique column
...ou will see this error with Entity Framework Code First:
Column 'x' in table 'dbo.y' is of a type that is invalid for use as a key column in an index.
The reason is because of this:
SQL Server retains the 900-byte limit for the maximum total size of all index key columns."
(from: http://...
Is there a way that I can check if a data attribute exists?
...
if ($("#dataTable").data('timer')) {
...
}
NOTE this only returns true if the data attribute is not empty string or a "falsey" value e.g. 0 or false.
If you want to check for the existence of the data attribute, even if empty, do th...
Python Requests and persistent sessions
...= s.get('https://localhost/profile_data.json', ...)
#cookies sent automatically!
#do whatever, s will keep your cookies intact :)
For more about sessions: https://requests.kennethreitz.org/en/master/user/advanced/#session-objects
...
Image Greyscale with CSS & re-color on mouse-over?
...rayscale(100%);
/* Chrome 19+ & Safari 6+ */
-webkit-transition: all .6s ease;
/* Fade to color for Chrome and Safari */
-webkit-backface-visibility: hidden;
/* Fix for transition flickering */
}
img.grayscale:hover {
filter: none;
-webkit-filter: grayscale(0%);
}
sv...
How to increase the vertical split window size in Vim
:vsplit (short form: :vs ) split the Vim viewport vertically. :30vs splits the viewport, making the new window 30 characters wide. Once this 30 char window is created, how would one change it's size to 31 or 29?
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Markdown and image alignment
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I like to be super lazy by using tables to align images with the vertical pipe (|) syntax. This is supported by some Markdown flavours (and is also supported by Textile if that floats your boat):
| I am text to the left |  |
or
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Why would $_FILES be empty when uploading files to PHP?
I have WampServer 2 installed on my Windows 7 computer. I'm using Apache 2.2.11 and PHP 5.2.11. When I attempt to upload any file from a form, it seems to upload, but in PHP, the $_FILES array is empty. There is no file in the c:\wamp\tmp folder. I have configured php.ini to allow file uploads...
Javascript - How to detect if document has loaded (IE 7/Firefox 3)
I want to call a function after a document loads, but the document may or may not have finished loading yet. If it did load, then I can just call the function. If it did NOT load, then I can attach an event listener. I can't add an eventlistener after onload has already fired since it won't get cal...
Finding the index of elements based on a condition using python list comprehension
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In Python, you wouldn't use indexes for this at all, but just deal with the values—[value for value in a if value > 2]. Usually dealing with indexes means you're not doing something the best way.
If you do need an API similar to Matlab's, you would use numpy, a packag...
Speed up the loop operation in R
... much guessing you eliminate.
Next, consider optimized packages: The data.table package can produce massive speed gains where its use is possible, in data manipulation and in reading large amounts of data (fread).
Next, try for speed gains through more efficient means of calling R:
Compile your...