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Does a foreign key automatically create an index?
...se through a FK-relationship, you'll often need to lookup a relating table and extract certain rows based on a single value or a range of values.
So it makes good sense to index any columns involved in a FK, but a FK per se is not an index.
Check out Kimberly Tripp's excellent article "When did SQ...
Casting a variable using a Type variable
...
Here is an example of a cast and a convert:
using System;
public T CastObject<T>(object input) {
return (T) input;
}
public T ConvertObject<T>(object input) {
return (T) Convert.ChangeType(input, typeof(T));
}
Edit:
Some p...
文本框输入十六进制，按字节通过蓝牙发送 · App Inventor 2 中文网
....BeforePicking() {
列表选择器1.Elements = 蓝牙客户端1.AddressesAndNames
}
when 列表选择器1.AfterPicking() {
if (蓝牙客户端1.Connect(列表选择器1.Selection)) {
标签1.Text = "已连接"
}
}
实验一：先看清两种发法的区别
不连...
How to scroll to bottom in a ScrollView on activity startup
...iew. On activity startup (method onCreate) I fill the ScrollView with data and want to scroll to the bottom.
9 Answers
...
How to set the thumbnail image on HTML5 video?
...Video First Frame as Thumbnail:
Add preload="metadata" to your video tag and the second of the first frame #t=0.5 to your video source:
<video width="400" controls="controls" preload="metadata">
<source src="https://www.w3schools.com/html/mov_bbb.mp4#t=0.5" type="video/mp4">
&...
Making your .NET language step correctly in the debugger
...at for dynamic-compiled code is 100% different between .NET 2 (PDB stream) and .NET 4 (IL DB I think they called it?)
The 'nop's sound about right. See rules for generating implicit sequence points below.
You don't actually need to emit things on different lines. By default, VS will step 'symbol-sta...
RuntimeError on windows trying python multiprocessing
I am trying my very first formal python program using Threading and Multiprocessing on a windows machine. I am unable to launch the processes though, with python giving the following message. The thing is, I am not launching my threads in the main module. The threads are handled in a separate modu...
How to change title of Activity in Android?
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setTitle not working for me, getSupportActionBar() and getActionBar() also nulls i cant set the title in runtime.
– Ninja Coding
Jan 26 '16 at 17:30
1
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App Inventor 2 KIO4_Gradient 拓展：布局中的颜色渐变 · App Inventor 2 中文网
...后将它和两种颜色组成的列表传给 Gradient。方向值可按 Android GradientDrawable.Orientation 的 1～8 选择：
when Screen1.Initialize() {
KIO4_Gradient1.Shape = 0
KIO4_Gradient1.Type = 0
KIO4_Gradient1.CornerRadius = 24
KIO4_Gradient1.Gradient(
水平布局_标题,
...
Hide Utility Class Constructor : Utility classes should not have a public or default constructor
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If this class is only a utility class, you should make the class final and define a private constructor:
public final class FilePathHelper {
private FilePathHelper() {
//not called
}
}
This prevents the default parameter-less constructor from being used elsewhere in your code. Ad...